WO2020124418A1

WO2020124418A1 - A hybrid anode, an electrode assembly and a direct-type fuel cell comprising the electrode assembly

Info

Publication number: WO2020124418A1
Application number: PCT/CN2018/122000
Authority: WO
Inventors: Renhe WANG; Mengjia WU; Yongyao Xia
Original assignee: Rhodia Operations; Fudan University
Priority date: 2018-12-19
Filing date: 2018-12-19
Publication date: 2020-06-25

Abstract

The present invention relates to a hybrid anode, an electrode assembly comprising the hybrid anode and a direct-type fuel cell comprising the electrode assembly. The hybrid anode comprises a first catalyst layer for the oxidation of a reductant, a second catalyst layer for the oxidation of H2, and a gas diffusion layer successively.

Description

A hybrid anode, an electrode assembly and a direct-type fuel cell comprising the electrode assembly

TECHNICAL FIELD

The present invention relates to a hybrid anode, an electrode assembly comprising the hybrid anode and a direct-type fuel cell comprising the electrode assembly.

BACKGROUND OF THE INVENTION

The following discussion of the prior art is provided to place the invention in an appropriate technical context and enable the advantages of it to be more fully understood. It should be appreciated, however, that any discussion of the prior art throughout the specification should not be considered as an express or implied admission that such prior art is widely known or forms part of common general knowledge in the field.

Fuel cells are a family of sustainable energy conversion technologies that generate electricity through electrochemical processes, rather than combustion. There are many fuel cell types, but the principal ones include alkaline fuel cells (AFCs) , proton exchange membrane fuel cells (PEMFCs) , direct methanol fuel cells (DMFCs) , molten carbonate fuel cells (MCFCs) , phosphoric acid fuel cells (PAFCs) , and solid oxide fuel cells (SOFCs) . Different fuel cells are applied in different ways owning to their specific operating characteristics. For example, the commercial use of AFCs is very limited and it is normally used in controlled aerospace and underwater environments because of its sensitiveness to carbon dioxide. The operating temperature of MCFCs and SOFCs is higher than other types of fuel cells, and therefore they are more suitable for large stationary applications. Direct-type fuel cells (DFCs) are widely used not only for stationary power plant but also for commercial fuel cell vehicles and typical temperature for that application is below 80℃. Direct methanol fuel cell (DMFCs) , which are one classical type among direct liquid type fuel cells, are specifically ideal for miniature applications at room temperature, such as cell phones and laptops. PAFCs are a type of fuel cell that uses liquid phosphoric acid as an electrolyte, which require higher loadings of expensive platinum catalyst than other types of fuel cells.

In the application of fuel cells, side reactions are always accompanied with the main reactions. Hydrogen evolution reaction (HER) is one of the important side reactions at anode, especially in the case when Pd catalyst is used. HER leads to a lot of issues in the practical use of fuel cells. The first one is the loss of electrons, which causes the decrease of efficiency of a fuel cell; the second one is the concern and management of H ₂ gas in the sealed pipeline, which might cause fuel leakage and failure of the fuel cells.

Naoko Fujiwara et al. ( “Rapid evaluation of the electrooxidation of fuel compounds with a multiple-electrode setup for direct polymer electrolyte fuel cells” , Journal of Power Source 164 (2007) 457-463) reported the electrochemical oxidation of some fuel candidates in acidic media. Noble metals were used as electrocatalysts and membrane electrode assemblies (MEAs) were prepared to run the fuel cell when hypophosphorous acid and phosphorous acid were applied as one family of the fuel compounds.

JP2011-060531 disclosed a DFC, which is characterized by the use of hypophosphorous acid, hypophosphite, ammonia or their mixture as fuel and an ion conductive polymer as electrolyte. The use of inorganic fuels eliminates carbon consumption and CO ₂ release in the atmosphere. On the other hand, since anion exchange membrane (AEM) is used instead of conventional sulfonic acid basedproton exchange membrane (PEM) , it becomes possible to avoid the using of precious electrode catalysts, such as Pt, Pd, Ir, Ru, Rh and Au. Cheap base metals, such as Ni, Ag, Co, Fe, Cu, Zn might also be considered.

There is no discussion in the Naoko Fujiwara’s article or JP2011-060531 about HER side reaction and efficiency of the fuel cells. In the article of R. Wang etc. “Hypophosphites as eco-compatible fuel for membrane-free direct liquid fuel cells” , Chem. Eur. J. 2018, 24, 10310-10314, the performance of direct hypophosphite fuel cell has been well studied and the fuel cell efficiencies are analyzed for the first time. The Faradic efficiency of direct hypophosphite fuel cell is quite low (26%in 10-hour discharge with 10 mA cm ^-2 current density and 100 mL fuel; 70%in 10 mA cm ^-2 discharge to 0 V with 10 mL fuel) . The low Faradic efficiency is a very obvious shortage in direct hypophosphite fuel cell technology.

Therefore, there is a need for a fuel cell having an improved Faradic efficiency and energy efficiency.

The present application provides a hybrid anode comprising a first catalyst layer for the oxidation of a reductant, a second catalyst layer for the oxidation of H ₂, and a gas diffusion layer, an electrode assembly comprising the hybrid anode and a direct-type fuel cell comprising the electrode assembly. By using the hybrid anode of the present application, the direct-type fuel cell can elevate about 3-folds of the faradic efficiency of the direct hypophosphite fuel cell and can also increase the energy efficiency of the cell. In addition, the added gas diffusion layer to the anode can protect the electrode, brings higher mechanical strength. This invention paved the way for wider practice of direct hypophosphite fuel cells.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 illustrates the structure of MEA D in the examples of the present disclosure.

Figure 2 shows the Faradic efficiencies in Example 1 after 3-hour discharging of 10 mL fuel with different MEAs at 10 mA cm ^-2.

Figure 3 shows the Faradic efficiencies in Example 2 after 1.5-hour discharging of 10 mL fuel with different MEAs at 20 mA cm ^-2.

Figure 4 shows the Faradic efficiencies in Example 3 after discharging to 0 V of 10 mL fuel with different MEAs at 10 mA cm ^-2.

DEFINITIONS

Throughout the description, including the claims, the term "comprising one" should be understood as being synonymous with the term "comprising at least one" , unless otherwise specified, and "between" should be understood as being inclusive of the limits.

It is specified that, in the continuation of the description, unless otherwise indicated, the values at the limits are included in the ranges of values which are given.

As used herein, the term “electrolyte” is an ion conducting medium that provides ionic conductivity between the anode and cathode portions of the fuel cell. The electrolyte medium may be any type of media that allows ionic conduction.

As used herein, the term “anode” means the electrode from which electrons migrate to the outside circuit and is the electrode where oxidation occurs.

As used herein, the term “cathode” means the electrode to which electrons migrate from the outside circuit and is the electrode where reduction occurs.

As used herein, the term “oxidizable compound” is a substance capable of being oxidized, or converted into an oxide.

As used herein, the term “metal complex” is a substance consisting of a central atom or ion, which is usually metallic and is called the coordination center, and a surrounding array of bound molecules or ions, that are in turn known as ligands or complexing agents.

As used herein, the term “metal alloy” is a metal alloy, which can be viewed as a solid metal-solid metal mixture wherein a primary metal acts as solvent while other metal (s) act (s) as solute; in a metal alloy and wherein the concentration of the metal solute does not exceed the limit of solubility of the metal solvent.

As used herein, the term “transition metals” refer to metals of group IB, IIB, IIIB, IVB, VB, VIB, VIIB and VIIIB. This group comprises the elements with atomic number 21 to 30 (Sc to Zn) , 39 to 48 (Y to Cd) , 72 to 80 (Hf to Hg) and 104 to 112 (Rfto Cn) .

As used herein, the term “Lanthanides” refer to metals with atomic number 57 to 71.

As used herein, the term “Actinides” refer to the metals with the atomic number 89 to 103.

As used herein, the term “fuel” refers to a reductant in anode. The terms “fuel” and “reductant” can be used interchangeably.

As used herein, the term “X-self standing film” means a porous thin film with X and reinforcement (such as PTFE, PVDF, polyolefin, poval, butadiene styrene rubber) , for example, X can represent for a catalyst such as Pt, Pd, Pt/C, Pd/C, or other materials such as C.

Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of present application to the extent that it may render a term unclear, the present description shall take precedence.

DETAILS OF THE INVENTION

In a first aspect, the present invention relates to a hybrid anode comprising a first catalyst layer for the oxidation of a reductant, a second catalyst layer for the oxidation of H ₂, and a gas diffusion layer successively.

In a second aspect, the present invention relates to an electrode assembly comprising:

(i) a hybrid anode,

(ii) an ion exchange membrane or a separator; and

(iii) a cathode configured and arranged for the reduction of an oxidant,

wherein the hybrid anode comprising a first catalyst layer for the oxidation of a reductant, a second catalyst layer for the oxidation of H ₂, and a gas diffusion layer successively.

In a third aspect, the present invention also relates to a direct-type fuel cell, comprising:

(a) a reductant;

(b) a solvent,

(c) an electrode assembly comprising

(i) a hybrid anode,

(ii) an ion exchange membrane or a separator; and

(iii) a cathode configured and arranged for the reduction of an oxidant,

wherein the hybrid anode comprising a first catalyst layer for the oxidation of a reductant, a second catalyst layer for the oxidation of H ₂, and a gas diffusion layer successively; and

(d) optionally electrolyte.

Hybrid anode

In present invention, electrode catalyst for the first catalyst for the hybrid anode may comprise metal element chosen from a group consisting of (i) Transition metals, (ii) Lanthanides, (iii) Actinides, (iv) Elements of Groups IA, IIA, IIIA, IVA, VA, VIA, VIIA of Periodic Table and (v) Any combination thereof.

Specifically, hydrogen is not included in metal element chosen in Group IA of the Periodic Table. Carbon is not included in metal element chosen in Group IVA of the Periodic Table. Nitrogen and phosphorus are not included in metal element chosen in Group VA of the Periodic Table. Oxygen, sulfur and selenium are not included in metal element chosen in Group VIA of the Periodic Table. Fluorine, chlorine, bromine and iodine are not included in metal element chosen in Group VIIA.

The metal elements for the purpose of the present invention are also referred to as metalloids. The term metalloid is generally designating an element which has properties between those of metals and non-metals. Typically, metalloids have a metallic appearance but are relatively brittle and have a moderate electrical conductivity. The six commonly recognized metalloids are boron, silicon, germanium, arsenic, antimony, and tellurium. Other elements also recognized as metalloids include aluminum, polonium, and astatine. On a standard periodic table all of these elements may be found in a diagonal region of the p-block, extending from boron at one end, to astatine at the other (as indicated above) .

Electrode catalyst for the first catalyst for anode of present invention may comprise metal element, which can be in the form of elemental metal, metal alloy, metal oxide or metal complex.

Electrode catalyst for the first catalyst for anode of present invention comprising metal element may be metal oxide compounds comprising typically at least one oxygen atom and at least one metal atom which are chemically bound to the oxygen atom. The metal atom comprised in the metal oxide can be notably transition metal element, post transition metal element, rare earth metal element or metalloid element.

Examples of metal oxide compounds notably are:

- Transition metal oxides, such as: titanium oxide (TiO ₂) , zinc oxide (ZnO) , zirconium oxide (ZrO ₂) and manganese oxide (MnO ₂) ;

- Post transition metal oxides, such as: aluminum oxide (Al ₂O ₃) ;

- Rare earth element oxides, such as: cerium oxide (CeO ₂) , lanthanium oxide (La ₂O ₃) , praseodymium oxide (Pr ₆O ₁₁) , neodymium oxide (Nd ₂O ₃) , yttrium oxide (Y ₂O ₃) , ruthenium oxide (RuO ₂) , europium oxide (Eu ₂O ₃) and samarium oxide (Sm ₂O ₃) ;

- Metalloid element oxides, such as: boron oxide (B ₂O ₃) and silicon oxide (SiO ₂) ;

- Perovskites, such as LaNiO ₃, LaCoO ₃.

The perovskite is any material with the same type of crystal structure as calcium titanium oxide (CaTiO ₃) , known as the perovskite structure, or ^XIIA ^2+VIB ⁴⁺X ^2- ₃with the oxygen in the face centers, while A and B can also be more than one elements. Example of the perovskite can be LaNiO ₃.

Electrode catalyst for the first catalyst for anode of present invention comprising metal element may be metal alloy. The metal alloy may be notably selected from the group consisting of Pt-Au, Pd-Au, Pt-Pd, Pd-Ni, Pt-Ni, Pt-Ru, Pd-Ru, Pd-Cu, Pd-Bi, Pd-Ce and Pt-Sn alloys.

In one embodiment, catalyst for the first catalyst for anode of present invention comprising metal element may further comprise non-metal elements, such as C, N and P. For example, non-metal element can be doped in the metal catalyst.

Electrode catalyst for the first catalyst for anode of present invention may also comprise non-metal element chosen in a group consisting of elements of Groups IA, IVA, VA, VIA, VIIA of Periodic Table or any combination thereof. Said catalyst preferably comprises non-metal elements, such as C, N and P and combinations thereof. More preferable catalyst comprising of non-metal elements is N-doped C or S-doped C.

In present invention, the first catalyst for anode may preferably comprise element chosen in a group consisting of elements of Groups IIIA, IVA, VA of Periodic Table and Transition metals.

Examples of the first catalyst of the anode notably are:

- Elemental metal comprise element chosen in a group consisting of Pd, Pt, Ru, Au, Rh, Ir, Bi, Sn, B and any combination thereof;

- Metal alloy, for example, Pd alloy, such as Pd-Au, Pd-B, Pd-Ru, Pd-Cu, Pd-Bi, Pd-Ni, Pd-Ce, Pd-Rh, Pd-Pb, Pd-W, PtRu-Pd, Pd-Pt and the like, or a Pt alloy such as Pt-Ru;

- Hydrogen storage alloy;

- Co-B-O compounds.

The above-mentioned metal or metal alloy are in the form of nanoparticles standalone or loaded on different substrate including one or more of activated carbon black, carbon nanofiber, carbon nanotube, graphene, WC/C, oxides (including CeO ₂, WO ₃, Al ₂O ₃ etc. ) and their mixtures.

In one embodiment, the first catalyst layer of the anode may comprise the first catalyst mentioned above and a substrate.

Preferably, the substrate of the first catalyst layer of the anode may be a porous substrate structures. The substrates may comprise one or more conducting materials prepared in a sheet, foam, grid, cloth or other similar structure. The cathode substrate can be chemically passive, and merely physically support the cathode catalyst and transmit electrons, and/or it can be chemically or electrochemically active, assisting in the cathode reaction, in pre-conditioning of fuel, in post-conditioning of cathode reaction products, in physical control of the location of the electrolyte and other fluids, and/or in other similarly useful processes. Cathode substrates can include stainless steel, nickel foam, sintered nickel powder, etched aluminum-nickel mixtures, metal screens, carbon fibers, and carbon cloth.

Methods for applying the first catalysts to the substrate include, for example, spreading, wet spraying, powder deposition, electro-deposition, evaporative deposition, dry spraying, decaling, painting, sputtering, low pressure vapor deposition, electrochemical vapor deposition, tape casting, screen printing, hot pressing and other methods.

When the substrates are used, the preferred range of the first catalyst loading amount may be in a range of 0.01 to 500 mg/cm ². More preferably, the catalyst loading amount may be in arange of 1 to 20 mg/cm ².

In one embodiment, the first catalyst for the first catalyst layer of the anode may also be coated on a gas diffusion layer or may be prepared into a self standing film.

As used herein, the gas diffusion layer may be made with porous conducting materials, such as carbon felt, carbon fibers, carbon paper, carbon free standing film, or carbon cloth. The carbon free standing film is a porous carbon-based thin film with conductive carbon materials (carbon black, acetylene black, carbon nanotube, carbon nanofiber, graphite, graphene) and reinforcement (PTFE, PVDF, polyolefin, poval, butadiene styrene rubber) .

For the preparation of carbon free-standing film, 160 mg XC-72 carbon, 200 mg PTFE (20 wt%, aq. ) and several drops (approximately 0.1 ml) of isopropyl alcohol were mixed to form a paste. The paste was then rolled into an integrated thin film of desired thickness (500um) and dried at room temperature for 24 hours.

The gas diffusion layer may have a microporous side and an carbon cloth opposite side. For example, the GDL-CT has a microporous side and a PTFE-treated carbon cloth opposite.

Methods for coating the first catalysts to the gas diffusion layer include, for example, spreading, wet spraying, powder deposition, electro-deposition, evaporative deposition, dry spraying, decaling, painting, sputtering, low pressure vapor deposition, electrochemical vapor deposition, tape casting, screen printing, hot pressing and other methods.

When the first catalyst of the anode is coated to the GDL layer, the preferred range of catalyst loading amount may be in a range of 0.01 to 500 mg/cm ^-2. More preferably, the catalyst loading amount may be in a range of 1 to 20 mg/cm ^-2.

The first catalyst layer for the oxidation of reductant of the anode may be a self standing film.

Examples of the first catalyst of the anode are preferably Pd, more preferably, a Pd self standing film.

In present invention, the second catalyst for the hybrid anode may preferably comprise element chosen in a group consisting of elements of Groups IIIA, IVA, VA of Periodic Table, Transition metals and Lanthanides.

Preferably, the second catalyst for the hybrid anode may comprise metal element chosen from a group consisting of Transition metals and Lanthanides, which can be in the form of elemental metal, metal alloy, metal oxide or metal complex.

It should be understood by the people skilled in the art that the first or second catalyst for anode mentioned above can be loaded on a support. The supports applied are not particularly limited. Typical example of supports can be carbon such as activated carbon black, carbon nanofiber, carbon nanotube, graphene, WC/C, oxide such as alumina, CeO ₂, WO ₃ and silica, and their mixtures, preferably is carbon.

Examples of the second catalyst for the hybrid anode notably are:

- metal element chosen from a group consisting of Pt, Pd, Ni, Ir, Ru, Rh and Au;

- metal alloy selected from a Pt based metal alloy such as Pt-Ru, Pt-Pd, Pt-Fe, Pt-Co, Pt-Ni, Pt-Au, Pt-Ag, Pt-Bi; a Ni based metal alloy such as Ni-Mo, Ni-Co, Co-Ni-Mo, Ni-Fe, Ni-Fe-Mo, Ni-Cu, Ni-Cr, Ni-Ti, Ni-La, Ni-Zn, Ni-Pb, Ni-N-carbon nanotube; a Pd based metal alloy such as Pd-Ru, Pd-Au, Pd-Cu, Pd-Bi, Pd-Ni, Pd-Ce, Pd-Rh, Pd-B, Pd-Pb, Pd-W, PtRu-Pd, Pd-Pt.

The above-mentioned metal or metal alloy can be in the form of nanoparticles standalone or loaded on different supports including one or more of activated carbon black, carbon nanofiber, carbon nanotube, graphene, WC/C, oxides (including CeO ₂, WO ₃, Al ₂O ₃ etc. ) and their mixtures.

More preferably, the second catalyst for the hybrid anode may comprise Pt or Pt-Ru.

The gas diffusion layer (GDL) in the present application may be made with porous conducting materials, such as carbon felt, carbon fibers, carbon paper, carbon free standing film, or carbon cloth. The carbon free standing film is a porous carbon-based thin film with conductive carbon materials (carbon black, acetylene black, carbon nanotube, carbon nanofiber, graphite, graphene) and reinforcement (PTFE, PVDF, polyolefin, poval, butadiene styrene rubber) .

The gas diffusion layer may have a microporous side and a carbon cloth opposite side. For example, the GDL-CT has a microporous side and a PTFE-treated carbon cloth opposite.

The second catalyst for the oxidation of H ₂ of the anode may be coated on the gas diffusion layer or may be prepared into a self standing film and then laminated with the gas diffusion layer. Preferably, the second catalyst for the oxidation of H ₂ of the anode is coated on the microporous side of the GDL layer.

Methods for coating the catalysts to the gas diffusion layer include, for example, spreading, wet spraying, powder deposition, electro-deposition, evaporative deposition, dry spraying, decaling, painting, sputtering, low pressure vapor deposition, electrochemical vapor deposition, tape casting, screen printing, hot pressing and other methods.

When the catalyst is coated to the GDL layer, the preferred range of catalyst loading amount may be in the range of 0.01 and 500 mg/cm ^-2. More preferably, the catalyst loading amount may be in a range of 1 and 20 mg/cm ^-2.

All typical methods for preparing an anode can be applied in the present application. The second catalyst for the oxidation of H ₂, such as Pt black, or Pt/C at any Pt ratio can be deposited on GDL, and then covered on or mixed with the first catalyst layer such as Pd. Preferably, the first catalyst is made into a free-standing film.

Electrode assembly

The first catalyst and the second catalyst for the hybrid anode, the gas diffusion layer and the hybrid anode comprised in the electrode assembly of the present application are as described above. In present invention, electrode catalyst for cathode may comprise metal element chosen from a group consisting of(i) Transition metals, (ii) Lanthanides, (iii) Actinides, (iv) Elements of Groups IA, IIA, IIIA, IVA, VA, VIA, VIIA of Periodic Table and (v) Any combination thereof.

Electrode catalyst for cathode of present invention may comprise metal element, which can be in the form of elemental metal, metal alloy, metal oxide or metal complex.

Electrode catalyst for cathode of present invention comprising metal element may be metal oxide compounds comprising typically at least one oxygen atom and at least one metal atom which are chemically bound to the oxygen atom. The metal atom comprised in the metal oxide can be notably transition metal element, post transition metal element, rare earth metal element or metalloid element.

Examples of metal oxide compounds notably are:

- Posttransition metal oxides, such as: aluminum oxide (Al ₂O ₃) ;

- Perovskites, such as LaNiO ₃, LaCoO ₃.

Electrode catalyst for cathode of present invention comprising metal element may be metal alloy. The metal alloy may be notably selected from the group consisting of Pt-Au, Pd-Au, Pt-Pd, Pd-Ni, Pt-Ni, Pt-Ru, Pd-Ru, Pd-Cu, Pd-Bi, Pd-Ce and Pt-Sn alloys.

In one embodiment, catalyst for cathode of present invention comprising metal element may further comprise non-metal elements, such as C, N and P. For example, non-metal element can be doped in the metal catalyst.

Electrode catalyst for cathode of present invention may also comprise non-metal element chosen in a group consisting of elements of Groups IA, IVA, VA, VIA, VIIA of Periodic Table or any combination thereof. Said catalyst preferably comprises non-metal elements, such as C, N and P and combinations thereof. More preferable catalyst comprising of non-metal elements is N-doped C or S-doped C.

In present invention, cathode catalyst may preferably comprise element chosen in a group consisting of elements of Groups IA, IIA, IIIA, IVA, VA, VIA, VIIA of Periodic Table, Transition metals and Lanthanides.

It should be understood by the people skilled in the art that the electrode catalyst for cathode mentioned above can be loaded on a support. The supports applied are not particularly limited. Typical example of supports can be carbon such as activated carbon black, carbon nanofiber, carbon nanotube, graphene, WC/C, oxide such as alumina, CeO ₂, WO ₃ and silica, and their mixtures, preferably is carbon.

Examples of cathode catalyst notably are:

- Elemental metal comprise element chosen in a group consisting of Pt, Pd, Ag, Ni, Ru, Ir, Os, Mn, La, Co, Ce and any combination thereof;

- Metal alloy, such as Pt-Ru, Pt-M (M=transition metals such as V, Cr, Co, Ni, Fe, Ti, Cu, Ag, Au, Mo, Mn, Al, etc. ) , Pd-Pt, Pd-Ru, Pd-Rh, PdRh ₃, Pd-M (M=Co, Fe, Ni, Cr, Mn, Ti, V, Sn, Cu, Ir, Ag, Rh, Au, Pt) alloys, Pd-Co-Au, Pd-Ni-P, Pd-Se, Pd-S, Pd-P and the like;

- Metal oxide, such as titanium oxide (TiO ₂) , zirconium oxide (ZrO ₂) , niobium oxide (Nb ₂O ₅) , manganese oxide (MnO ₂) , ruthenium oxide (RuO ₂) , cerium oxide (CeO) , europium oxide (Eu ₂O ₃) , samarium oxide (Sm ₂O ₃) , cobalt oxide (CoO) , cobaltic oxide (Co ₂O ₃) , Perovskites, such as LaNiO ₃, LaCoO ₃ and any combination thereof;

- M-N-C (M=Fe, Co, Cu, Cr and other transition metals, N is doped in carbon substrate such as activated carbon black, carbon nanofiber, carbon nanotube, graphene) ;

- Non-metal compound, such as N-doped C and S-doped C.

The above-mentioned metal or metal alloy are in the form of nanoparticles standalone or loaded on different supports including one or more of activated carbon black, carbon nanofiber, carbon nanotube, graphene, WC/C, oxides (including CeO ₂, WO ₃, Al ₂O _3, etc. ) and their mixtures.

In one embodiment, the cathode may comprise catalyst mentioned above and a substrate.

Preferably, the cathode can be made with porous substrate structures. The cathode substrates may comprise one or more conducting materials prepared in a sheet, foam, grid, cloth or other similar structure. The cathode substrate can be chemically passive, and merely physically support the cathode catalyst and transmit electrons, and/or it can be chemically or electrochemically active, assisting in the cathode reaction, in pre-conditioning of fuel, in post-conditioning of cathode reaction products, in physical control of the location of the electrolyte and other fluids, and/or in other similarly useful processes. Cathode substrates can include stainless steel, nickel foam, sintered nickel powder, etched aluminum-nickel mixtures, metal screens, carbon fibers, and carbon cloth.

Methods for applying the cathode catalysts to the cathode substrate include, for example, spreading, wet spraying, powder deposition, electro-deposition, evaporative deposition, dry spraying, decaling, painting, sputtering, low pressure vapor deposition, electrochemical vapor deposition, tape casting, screen printing, hot pressing and other methods.

When cathode substrates are used, the preferred range of catalyst loading amount may be in a range of 0.01 to 500 mg/cm ². More preferably, the catalyst loading amount may be in a range of 1 to 20 mg/cm ².

In one embodiment, the catalyst for cathode may also be coated on a gas diffusion layer or may be prepared into a self standing film and then laminated with the gas diffusion layer. Preferably, the catalyst for cathode is coated on the microporous side of the gas diffusion layer.

Methods for coating the cathode catalysts to the gas diffusion layer include, for example, spreading, wet spraying, powder deposition, electro-deposition, evaporative deposition, dry spraying, decaling, painting, sputtering, low pressure vapor deposition, electrochemical vapor deposition, tape casting, screen printing, hot pressing and other methods.

When the cathode catalyst is coated to the GDL layer, the preferred range of catalyst loading amount may be in a range of 0.01 to 500 mg/cm ^-2. More preferably, the catalyst loading amount may be in a range of 1 to 20 mg/cm ^-2.

The ion exchange membrane can be an anion exchange membrane or a cation exchange membrane. Preferably, the ion exchange membrane is an anion exchange membrane.

In another preferred embodiment, anode and cathode reside in two independent apartments, where a separator can be placed between the two compartments. As used herein "separator" should be understood as a layer that provides a physical separation between the anode and the cathode and acts as an electrical insulator between the two conductive electrodes. It has pores big enough for the fuel or electrolyte solution to go through. In this equipment, reductant and oxidant might exist in two compartments. But it’s still possible for reductant and oxidant freelyto communicate between the anode and cathode.

The difference between separator and ion-exchange membrane is that it is not selective to ions and it allows fuel molecules to flow freely between the anode and the cathode. Because of this difference, the separator is much cheaper andmuch less resistive than the ion-exchange membrane.

The materials of separator are not particularly limited. Examples of separators include dielectric materials such as nonwoven fibers like cotton, nylon, polyesters, glass, polymer like polyethylene, polypropylene, poly (tetrafluoroethylene) , polyvinyl chloride or naturally occurring substances like rubber, asbestos, wood.

Separators can consist of a single or multiple layers/sheets of same or different materials.

In present invention, if a separator is used, the distance between the two electrodes may be in a range of 0.1 to 10 cm and preferably in a range of 0.2 to 2 cm.

All typical methods for preparing an electrode assembly can be applied in the present application, such as those mentioned in “Principles of MEA preparation” , from “Handbook of Fuel Cells-Fundamentals, Technology and Applications” , edited by Wolf Vielstich, Hubert A. Gasteiger, Arnold Lamm and Harumi Yokokawa @2010 John Wiley&Sons, Ltd. ISBN: 978-0-470-97400-1.

Direct-type fuel cell

The first catalyst and the second catalyst for the hybrid anode, the hybrid anode, the ion exchange membrane or the separator, the cathode or the electrode assembly comprised in the direct-type fuel cell of the present application are as described above.

The reductant, which is the fuel of the direct-type fuel cell can be an oxidizable compound chosen from the group consisting of phosphorus compound, sulphur compound, nitrogen compound and any combination thereof.

In present invention, oxidizable phosphorus compound, sulphur compound, nitrogen compound might be inorganic or organic compound.

Oxidizable phosphorus compound of present invention might be hypophosphorous acid compound or phosphorous acid compound.

Hypophosphorous acid compound of the present invention may be hypophosphorous acid or its derivatives. Hypophosphorous acid derivatives of present invention may notably be salts of hypophosphorous acid.

Examples of hypophosphorous acid salts notably are:

- Alkali metal salts, such as lithium hypophosphite (LiH ₂PO ₂) , sodium hypophosphite (NaH ₂PO ₂) , potassium hypophosphite (KH ₂PO ₂) ;

- Alkaline earth metal salts, such as beryllium hypophosphite (Be (H ₂PO ₂) ₂) , magnesium hypophosphite (Mg (H ₂PO ₂) ₂) , calcium hypophosphite (Ca (H ₂PO ₂) ₂) ;

- Ammonium hypophosphite (NH ₄H ₂PO ₂) .

Among these, lithium hypophosphite (LiH ₂PO ₂) , sodium hypophosphite (NaH ₂PO ₂) , potassium hypophosphite (KH ₂PO ₂) and ammonium hypophosphite (NH ₄H ₂PO ₂) are particularly preferred.

Phosphorous acid compound of the present invention may be phosphorous acid or its derivatives. Phosphorous acid derivatives of present invention may be salts of phosphorous acid.

Examples of phosphorous acid salts notably are:

- Alkali metal salts, such as lithium phosphite (Li ₃PO ₃) , lithium hydrogen phosphite (Li ₂HPO ₃) , lithium dihydrogen phosphite (LiH ₂PO ₃) , sodium phosphite (Na ₃PO ₃) , sodium hydrogen phosphite (Na ₂HPO ₃) , sodium dihydrogen phosphite (NaH ₂PO ₃) , potassium phosphite (K ₃PO ₃) , potassium hydrogen phosphite (K ₂HPO ₃) and potassium dihydrogen phosphite (KH ₂PO ₃) ;

- Alkaline earth metal salts, such as beryllium phosphite (Be ₃ (PO ₃) ₂) , magnesium phosphite (Mg ₃ (PO ₃) ₂) and calcium phosphite (Ca ₃ (PO ₃) ₂) ;

- Ammonium phosphite ( (NH ₄) ₃PO ₃) .

Among these, lithium phosphite (Li ₃PO ₃) , sodium phosphite (Na ₃PO ₃) , potassium phosphite (K ₃PO ₃) and ammonium phosphite ( (NH ₄) ₃PO ₃) are particularly preferred.

Oxidizable sulphur compound of present invention may be sulphurous acid compound or thiosulfuric acid compound.

Sulphurous acid compound of the present invention may be sulphurous acid or its derivatives. Sulphurous acid derivatives of present invention may notably be sulphites.

Examples of sulphites notably are:

- Alkali metal salts, such as lithium sulphite (Li ₂SO ₃) , sodium sulphite (Na ₂SO ₃) and potassium sulphite (K ₂SO ₃) ;

- Alkaline earth metal salts, such as beryllium sulphite (BeSO ₃) , magnesium sulphite (MgSO ₃) and calcium sulphite (CaSO ₃) ;

- Ammonium sulphite ( (NH ₄) ₂SO ₃) .

Among these, lithium sulphite (Li ₂SO ₃) , sodium sulphite (Na ₂SO ₃) , potassium sulphite (K ₂SO ₃) and ammonium sulphite ( (NH ₄) ₂SO ₃) are particularly preferred.

Thiosulfuric acid compound of the present invention may be thiosulfuric acid and its derivatives. Thiosulfuric acid derivatives of present invention may be thiosulfates.

Examples of thiosulfates notably are:

- Alkali metal salts, such as lithium thiosulfate (Li ₂S ₂O ₃) , sodium thiosulfate (Na ₂S ₂O ₃) , potassium thiosulfate (K ₂S ₂O ₃) ;

- Alkaline earth metal salts, such as beryllium thiosulfate (BeS ₂O ₃) , magnesium thiosulfate (MgS ₂O ₃) , calcium thiosulfate (CaS ₂O ₃) ;

- Ammonium thiosulfate ( (NH ₄) ₂ S ₂O ₃) .

Among these, lithium thiosulfate (Li ₂S ₂O ₃) , sodium thiosulfate (Na ₂S ₂O ₃) , potassium thiosulfate (K ₂S ₂O ₃) and ammonium thiosulfate ( (NH ₄) ₂ S ₂O ₃) are particularly preferred.

In present invention, oxidizable nitrogen compound might be nitrous compound or amine.

Nitrous compound of present invention may be nitrous acid or its derivatives. Nitrous acid derivatives of present invention may be salts of nitrous acid.

Example of nitrous acid salts notably are:

- Alkali metal salts, such as lithium nitrite (LiNO ₂) , sodium nitrite (NaNO ₂) and potassium nitrite (KNO ₂) ;

- Alkaline earth metal salts, such as beryllium nitrite (Be (NO ₂) ₂) , magnesium nitrite (Mg (NO ₂) ₂) and calcium nitrite (Ca (NO ₂) ₂) ;

- Ammonium nitrite (NH ₄NO ₂) .

Among these, lithium nitrite (LiNO ₂) , sodium nitrite (NaNO ₂) , potassium nitrite (KNO ₂) and ammonium nitrite (NH ₄NO ₂) are particularly preferred.

Amine of present invention may be ammonia or organic amine, such as alkylamines, arylamines. Among these, ammonia is particularly preferred.

The reductant can also be an oxidizable compound chosen from the group consisting of borohydride salt, ammonia borane, formic acid, formate and hydrazine hydrate, and organic chemical hydride.

Examples of borohydride salt notably are:

- Alkali metal salts, such as lithium borohydride (LiBH ₄) , sodium borohydride (Na BH ₄) and potassium borohydride (KBH ₄) ;

- Alkaline earth metal salts, such as beryllium borohydride (Be (BH ₄) ₂) , magnesium borohydride (Mg (BH ₄) ₂) and calcium borohydride (Ca (BH ₄) ₂) .

Examples of formates notably are:

- Alkali metal salts, such as lithium formate (HCOOLi) , sodium formate (HCOONa) and potassium formate (HCOOK) ;

- Alkaline earth metal salts, such as beryllium formate (Be (HCOO) ₂) , magnesium formate (Mg (HCOO) ₂) and calcium formate (Ca (HCOO) ₂) ;

- Ammonium formate (HCOONH ₄) .

Examples of organic chemical hydride notably are:

- Cyclic hydrocarbons, such as cyclohexane, methylcyclohexane, cylohexene, 2-propanol, cyclohexanol, and decalin.

It should be understood that the fuel of the present invention may include one or several compounds above mentioned, in which any molar ratio or weight ratio of combinations thereof are contemplated as included within the scope of the invention.

In present invention, the oxidant used in the fuel cell can be organic or inorganic oxidizing agent. Preferably, oxidant can be chosen in a group consisting of hydrogen peroxide, oxygen and air.

The solvent for dissolving the fuel is not particularly limited. Any suitable solvent, such as water and hydrophilic organic solvent can be used. Examples of hydrophilic organic solvent are alcohols, such as methanol, ethanol, n-propanol, and isopropyl alcohol. It should be understood that the solvent mentioned above can be used independently or in the form of mixtures.

The concentration of the fuel in solution is preferably in a range of 0.01 M to 15 M. In one embodiment, a saturated solution might be used.

In present invention, an electrolyte may be optionally added to the solution. The electrolyte medium may be alkaline or acidic in nature. Preferred electrolyte is alkali metal hydroxide, such as lithium hydroxide (LiOH) , sodium hydroxide (NaOH) or potassium hydroxide (KOH) , alkali metal bicarbonate, such as sodium bicarbonate (NaHCO ₃) or potassium bicarbonate (KHCO ₃) , alkali metal carbonate, such as lithium carbonate (Li ₂CO ₃) , sodium carbonate (Na ₂CO ₃) or potassium carbonate (K ₂CO ₃) .

In one embodiment, additives might also been added to avoid competitive reaction or stabilize the fuel, such as thiourea, glycerol, etc. Said competitive reaction particularly refers to hydrogen evolution reaction, which is the production of hydrogen through the process of water electrolysis.

All typical methods for preparing a direct type fuel cell can be applied in the present application. For example, the single cell components include the stainless steel plate, plastic plate, anode current collector, anode plate, gasket, MEA, gasket, cathode plate, cathode current collector, plastic plate and stainless steel plate. The graphite anode/cathode plates and the current collectors are isolated from the stainless steel ends by the plastic plates. The flow fields are built in the graphite plates. Gaskets are used to seal the MEA. The single cell is compressed and sealed under the pressure of 2 N. m.

The following examples are included to illustrate embodiments of the invention. Needless to say, the invention is not limited to the described examples.

Test method:

NMR spectra analysis for Faradaic efficiency

³¹P NMR spectra were recorded on Bruker AVIII spectrometers at 300MHz for ³¹P IG (Inverse Gated Decoupling) . The chemical shift of the hypophosphite andits two oxidation compounds in strongly alkaline solution are listed as below. The reference of the chemical shifts is 85%phosphoric acid (recorded by instrument after once) . The small resonances symmetrically distributed around main peaks in decoupled spectra were residual coupling. This phenomenon is caused by large P-H coupling constant and can be removed in coupled spectra. The chemical yield of different P species is calculated by the area of correspondingpeaks.

NaH ₂PO ₂ (P ^I) : ³¹P-NMR (IG, 300 MHz, D ₂O) : δ=7.7;

Na ₂HPO ₃ (P ^III) : ³¹P-NMR (IG, 300 MHz, D ₂O) : δ=3.5;

Na ₃PO ₄ (P ^V) : ³¹P-NMR (IG, 300 MHz, D ₂O) : δ=5.3

The chemical yield can be calculated by:

where

stands for the mole of different phosphorous species yield in discharged fuel.

The Faradaic efficiency can be calculated:

where i stands for discharging current, t stands for discharging time, 96485 is the Faraday constant.

The electricity loss results from two parts: one is left in fuel as unconverted P species as P ^I or P ^III; one is lost during discharge, which can be ascribed to the chemical hydrogen evolution and dissipation on Pd surface, resulting in electrons uncollected during the conversion of P species.

The electricity left in fuel can be calculated as:

The electricity lost during discharge:

The energy efficiency is calculated as

Where i is the current value for constant discharge, V (t) is the time-dependent voltage, t is the discharging time.

is the enthalpy correlating to the conversion of hypophosphite to phosphite (-402.17 kJ/mol) ,

is the total mole of phosphite and phosphate, which is the total mole of converted hypophosphite. Similarly,

is the enthalpy of the conversion from phosphite to phosphate (-286.37 kJ/mol) , while

represents the mole of phosphate.

Examples

Example 1

Discharging test of 10mL fuel at a current density of 10 mA cm ^-2 with Hybrid anode based on Pt coated gas diffusion layer and Pd free standing film for 3-hours.

In this example, five MEAs (Membrane Electrode Assemblies) were prepared by Pd/C-based free-standing films as anode, anion exchange membrane (FumaTech FAA3PK130) and PtGDL (Pt coated Gas Diffusion Layer, provided by FuelCellsEtc., the Pt is coated on the microporous side of the GDL and the Pt loading is 4 mg cm ^-2) as cathode. The overall MEA is made by pressing the laminated anode, anion exchange membrane and cathode together under the pressure of 6 MPa. The active area of the MEA A is 2.25 cm ².

For the preparation of Pd free-standing film (PdFSF) , 160 mg Pd/C catalyst (Pd loading 20 wt%) , 200 mg PTFE (20 wt%, aq. ) (diluted from 60%PTFE dispersion with water) and several drops (approximately 0.1 ml) of isopropyl alcohol were mixed to form a paste. The paste was then rolled into an integrated thin film and dried at room temperature for 24 hours. The dried film was cut into a size of 1.5 x 1.5 cm ² (=2.25 cm ²) for cell tests. The Pd loading of the PdFSF is then controlled to be 1 mg cm ^-2.

For the preparation of Pt free-standing film (PtFSF) , 120 mg Pt black, 96 mg Vulcan XC-72 carbon, 120 mg PTFE (20 wt%, aq. ) (diluted from 60%PTFE dispersion with water) and several drops (approximately 0.1 ml) of isopropyl alcohol were mixed to form a paste. The paste was then rolled into an integrated thin film and dried at room temperature for 24 hours. The dried film was cut into a size of 1.5 x 1.5 cm ² (=2.25 cm ²) for cell tests. The Pt loading of the PtFSF is then controlled to be 4 mg cm ^-2.

For the preparation of Pd+Pt free-standing film ( (Pd+Pt) FSF) , 120 mg Pt/C catalyst (Pt loading 20 wt%) and 40 mg Pd/C catalyst (Pd loading 20 wt%) were mixed with 250 mg PTFE (20 wt%, aq. ) (diluted from 60%PTFE dispersion with water) and several drops (approximately 0.1 ml) of isopropyl alcohol to form the paste. The paste was then rolled into an integrated thin film and dried at room temperature for 24 hours. The dried film was cut into a size of 1.5 x 1.5 cm ²(=2.25 cm ²) for cell tests. The Pd loading of the mixed free-standing film is 1 mg cm ^-2 and the Pt loading is 4 mg cm ^-2.

In MEA A, bare PdFSF was used as anode electrode, the PdFSF (Pd loading=1.0 mg cm ^-2) was pressed under the pressure of 6 MPa with anion exchange membrane and PtGDL (as cathode, Pt loading=4 mg cm ^-2) . The active area of MEA A is 2.25 cm ².

In MEA B, mixed catalyst free-standing film ( (Pd+Pt) FSF) was used as anode electrode, the mixed free-standing film and the anion exchange membrane and the PtGDL (as cathode, Pt loading=4mg cm ^-2) were pressed together under the pressure of 6 MPa. The active area of the MEA B is 2.25 cm ².

In MEA C, a PtFSF (Pt loading=4 mg cm ^-2) was stacked on the configuration of MEA A, in which PtFSF, PdFSF, anion exchange membrane and PtGDL (the sequence is followed as mentioned from anode side to cathode side, the microporous side of PtGDL or GDL always oriented to the membrane) were laminated and pressed under the pressure of 6 MPa. The active area of the MEA C is 2.25 cm ².

In MEA D, a PtGDL (Pt loading=4 mg cm ^-2) was stacked on the configuration of MEA A, in which PtGDL, PdFSF, anion exchange membrane and PtGDL (the sequence is followed as mentioned from anode side to cathode side, the microporous side of PtGDL or GDL always oriented to the membrane) were laminated and pressed under the pressure of 6 MPa. The active area of the MEA D is 2.25 cm ². The structure of MEA D was shown in Figure 1, wherein 1 stands for PtGDL, 2 stands for Anion Exchange Membrane, and 3 stands for PdFSF.

In MEA E, a bare GDL was stacked on the configuration of MEA A, in which GDL, PdFSF, anion exchange membrane and PtGDL (the sequence is followed as mentioned from anode side to cathode side, the microporous side of PtGDL or GDL always oriented to the membrane) were laminated and pressed under the pressure of 6 MPa. The active area of the MEA E is 2.25 cm ².

Fuel cell tests were conducted under the following conditions: 10 mL aqueous fuel (0.5 mol/LNaH ₂PO ₂ and 1 mol/L KOH) was delivered to the anode at a constant flow rate of 12 mL min ^-1, while pure air was spontaneously diffused to the cathode at a flow rate of 100 mL min ^-1. Fuel cell performances were evaluated at room temperature (25℃) with Metrohm Autolab PGSTAT 302N.

In the polarization tests, the MEA A, B, C, D and E reached the maximum power density of 55, 58, 17, 38, 10 mW cm ^-2, respectively. After 3-hour discharge with current density of 10 mA cm ^-2, the Faradic efficiencies of MEA A, B, C, D and E were of 27%, 28%, 44%, 78%and 36%, respectively as shown in Fig. 2.

Example 2

Discharging test of 10mL fuel at a current density of 20 mAcm ^-2 with Hybrid anode based on Pt coated gas diffusion layer and Pd free standing film for 1.5-hours.

In this example, five MEAs (Membrane Electrode Assemblies) were preparedby Pd/C-based free-standing films as anode, anion exchange membrane (fumatech FAA3PK130) and PtGDL (Pt coated Gas Diffusion Layer, provided by FuelCellsEtc., the Pt is coated on the microporous side of the GDL and the Pt loading is 4 mg cm ^-2) as cathode. The overall MEA is made by pressing the laminated anode, anion exchange membrane and cathode together under the pressure of 6 MPa. The active area of the MEA A is 2.25 cm ².

For the preparation of Pd+Pt free-standing film ( (Pd+Pt) FSF) , 120 mg Pt/C catalyst (Pt loading 20 wt%) and 40 mg Pd/C catalyst (Pd loading 20 wt%) were mixed with 250 mg PTFE (20 wt%, aq. ) (diluted from 60%PTFE dispersion with water) and several drops (approximately 0.1 ml) of isopropyl alcohol to form the paste. The paste was then rolled into an integrated thin film and dried at room temperature for 24 hours. The dried film was cut into a size of 1.5 x 1.5 cm ² (=2.25 cm ²) for cell tests. The Pd loading of the mixed free-standing film is 1 mg cm ^-2 andthe Pt loading is 4 mg cm ^-2.

In MEA D, a PtGDL (Pt loading=4 mg cm ^-2) was stacked on the configuration of MEA A, in which PtGDL, PdFSF, anion exchange membrane and PtGDL (the sequence is followed as mentioned from anode side to cathode side, the microporous side of PtGDL or GDL always oriented to the membrane) were laminated and pressed under the pressure of 6 MPa. The active area of the MEA D is 2.25 cm ².

In the polarization tests, the MEA A, B, C, D and E reached the maximum power density of 55, 58, 17, 38, 10 mW cm ^-2, respectively. After 1.5-hour discharge with current density of 20 mA cm ^-2, the Faradic efficiencies of MEA A, B, C, D and E were of 37%, 37%, 64%, 87%and 48%, respectively as shown in Fig. 3.

Example 3

Discharging test of 10mL fuel at a current density of 10 mA cm ^-2 with Hybrid anode based on Pt coated gas diffusion layer and Pd free standing film to 0 V.

In the polarization tests, the MEA A, B, C, D and E reached the maximum power density of 55, 58, 17, 38, 10 mW cm ^-2, respectively. After discharge with current density of 10 mA cm ^-2 to 0 V, the Faradic efficiencies of MEA A, B, C, D and E were of 64%, 64%, 77%, 91%and 70%, respectively as shown in Fig. 4.

As Table 1 has shown, the energy efficiencies of MEAs with Pt catalyst layer are notably higher than MEAs with open structure in all the discharge conditions. Generally, the improved hybrid electrodes show>15%energy efficiency, and over 30%in the best cases.

Table 1. Energy efficiencies of MEA A, C and D in different discharge conditions

Claims

A hybrid anode comprising a first catalyst layer for the oxidation of a reductant, a second catalyst layer for the oxidation of H ₂, and a gas diffusion layer successively.
The hybrid anode according to claim 1, wherein the first catalyst comprises metal element chosen from a group consisting of (i) Transition metals, (ii) Lanthanides, (iii) Actinides, (iv) Elements of Groups IA, IIA, IIIA, IVA, VA, VIA, VIIA of Periodic Table and (v) Any combination thereof.
The hybrid anode according to any one of claims 1 to 2, wherein the first catalyst comprise non-metal element chosen in a group consisting of elements of Groups IA, IVA, VA, VIA, VIIA of Periodic Table or any combination thereof.
The hybrid anode according to any one of claims 1 to 3, wherein the first catalyst comprises elemental metal comprising element chosen from a group consisting of Pd, Pt, Ru, Au, Rh, Ir, Bi, Sn, B and any combination thereof; a Pd alloy chosen from a group consisting of Pd-Au, Pd-BPd-Ru, Pd-Cu, Pd-Bi, Pd-Ni, Pd-Ce, Pd-Rh, Pd-Pb, Pd-W, PtRu-Pd, and Pd-Pt; a Pt alloy chosen from a group consisting of Pt-Ru; hydrogen storage alloy and Co-B-O compounds.
The hybrid anode according to any one of claims 1 to 4, wherein the second catalyst comprises element chosen in a group consisting of elements of Groups IIIA, IVA, VA of Periodic Table, Transition metals and Lanthanides.
The hybrid anode according to any one of claims 1 to 5, wherein the second catalyst comprises metal element chosen from a group consisting of Pt, Pd, Ni, Ir, Ru, Rh and Au or metal alloy selected from a Ni based metal alloy, Pd based metal alloy and Pt based metal alloy.
The hybrid anode according to any one of claims 1 to 6, wherein the gas diffusion layer is made with porous conducting materials.
The hybrid anode according to any one of claims 1 to 7, wherein the gas diffusion layer is made with carbon felt, carbon fibers, carbon paper, carbon free standing film, or carbon cloth.
The hybrid anode according to any one of claims 1 to 8, wherein the first catalyst and/or the second catalyst is applied to a support.
An electrode assembly comprising:

(i) a hybrid anode according to any one of claims 1-9,

(ii) an ion exchange membrane or a separator; and

(iii) a cathode configured and arranged for the reduction of an oxidant.
The electrode assembly according to claim 10, wherein the exchange membrane is an anion exchange membrane.
The electrode assembly according to claim 10 or 11, wherein cathode comprises a catalyst comprising metal element chosen from a group consisting of (i) Transition metals, (ii) Lanthanides, (iii) Actinides, (iv) Elements of Groups IA, IIA, IIIA, IVA, VA, VIA, VIIA of Periodic Table and (v) Any combination thereof.
The electrode assembly according to any one of claims 10-12, wherein cathode comprises a catalyst comprising non-metal element chosen in a group consisting of elements of Groups IA, IVA, VA, VIA, VIIA of Periodic Table or any combination thereof.
The electrode assembly according to any one of claims 10-13, wherein cathode comprises a catalyst selected from the group consisting of elemental metal chosen from a group consisting of Pt, Pd, Ag, Ni, Ru, Ir, Os, Mn, La, Co, Ce and any combination thereof; metal alloy; metal oxide, M-N-C (M=Fe, Co, Cu, Cr and other transition metals, N is doped in carbon substrate.
The electrode assembly according to any one of claims 10-14, wherein the separator is chosen in a group consisting of fibers, polymers and naturally occurring substances.
A direct-type fuel cell, comprising:

(a) a fuel;

(b) a solvent,

(c) an electrode assembly according to any one of claims 9-15;

(d) optionally electrolyte.
The direct-type fuel cell according to claim 16, wherein the fuel is a reductant being oxidizable compound chosen in a group consisting of phosphorus compound, sulphur compound, nitrogen compound and any combination thereof.
The direct-type fuel cell according to claim 16, wherein the fuel is hypophosphorous acid compound or phosphorous acid compound.
The direct-type fuel cell according to claim 18, wherein the hypophosphorous acid compound is chosen in a group consisting of hypophosphorous acid, its alkali metal salts, its alkaline earth metal salts, its ammonium salt and any combination thereof.
The direct-type fuel cell according to claim 17, wherein the sulphur compound is sulphurous acid compound or thiosulfuric acid compound.
The direct-type fuel cell according to claim 17, wherein the nitrogen compound is chosen in a group consisting of nitrous acid, its alkali metal salts, its alkaline earth metal salts, its ammonium salt and any combination thereof.
The direct-type fuel cell according to claim 16, wherein the fuel is an oxidizable compound chosen from the group consisting of borohydride salt, ammonia borane, formic acid, formate and hydrazine hydrate, and organic chemical hydride.