CN106268798A

CN106268798A - Pd/WO for formic acid oxidation3rGO catalyst and preparation method thereof

Info

Publication number: CN106268798A
Application number: CN201610567725.8A
Authority: CN
Inventors: 刘义林
Original assignee: Individual
Current assignee: Individual
Priority date: 2016-07-18
Filing date: 2016-07-18
Publication date: 2017-01-04

Abstract

The present invention relates to a kind of catalyst, particularly to a kind of Pd/WO for formic acid oxidation₃RGO catalyst and preparation method thereof.A kind of Pd/WO for formic acid oxidation₃RGO catalyst, this catalyst is to be prepared by following methods: take graphene oxide at the AMT(ammonium metatungstate that mass concentration is 10% 30%) solution impregnates, Hydrothermal Synthesis processes and obtains WO₃GO carrier, then carries out potassium borohydride reduction method synthesis Pt-supported catalyst.Chemical property, the X-ray diffraction of catalyst are characterized by the present invention with scanning electron microscope, and Study of Support is on the impact of composite catalyst performance and the catalyst comparative study to formic acid oxidation electrocatalysis characteristic.Result shows, Pd/WO₃RGO catalyst has chemical property and the stability of optimum, and the catalyst performance that Graphene is carrier is more preferable compared with CNT.

Description

Pd/WO for formic acid oxidation3-RGO catalyst and preparation method thereof

Technical field

The present invention relates to a kind of catalyst, particularly to a kind of Pd/WO for formic acid oxidation₃-RGO catalyst and system thereof Preparation Method.

Background technology

Society, serious due to the destruction of ecological environment and environmental pollution, research and development new forms of energy become works as The severe problem of modern facing mankind.In order to efficiently solve this problem, using clean reproducible energy is only selection, Wherein the most prominent with fuel cell.Chemical energy is converted into electric energy by fuel battery energy efficiently, has specific energy high, to environment The features such as destructive power is little, long service life, composition simple, is easily portable, can play more at compact power, electric automobile Big potentiality, therefore become current study hotspot.

Direct methanoic acid fuel cell has more advantage: 1) formic acid is nontoxic, and burning-point is higher, storage and convenient transportation；2) first Acid is a kind of electrolyte, can strengthen the proton conductivity of solution in anode chamber；3) carboxyl in formic acid and the sulfonic group of Nafion Group is mutually exclusive, low to the permeability of Nafion membrane；4) concentration of the permeability permission formic acid of lower Nafion is higher, Therefore DFAFC has higher energy density；5) relatively low permeability can reduce the anticathode interference of fuel crossover film, thus subtracts The waste of few fuel.Therefore, direct methanoic acid fuel cell (DFAFC) has wide Research Prospects.

CNT, activated carbon, white carbon black etc. is all the most conventional carrier.Graphene as a kind of new carbon, because of It has the graphite plane structure of uniqueness, good electric conductivity (10³-10⁴And high specific surface area (2630m S/m)²/ g), more To be used as electro-catalyst carrier manyly.

Precious metals pd has more satisfactory catalysis behavior in terms of the electro-catalysis of formic acid.Therefore, urging of noble metal is improved Change the emphasis that performance is also research.But due to reasons such as Pd metal price are higher, less stable, the modified Pd catalyst of preparation is One research emphasis.Research shows, the modified catalyst that metal Pd and other metals form can be that catalyst provides bigger ratio Synergism between surface area, good dispersibility, suitable ion diffusion electrode skeleton and carrier and noble metal, so that improving The catalytic performance of catalyst, the stability of raising catalyst.It is thus possible to develop the modified noble metal catalyst of excellent performance, Make to keep the good performance of noble metal catalyst while reducing noble metal carrying capacity.Finally can be widely applied to each Field.

Summary of the invention

The present invention provides a kind of Pd/WO for formic acid oxidation₃-RGO catalyst, this catalyst has the electrochemistry of optimum Performance and stability.

The technical solution adopted for the present invention to solve the technical problems is:

A kind of Pd/WO for formic acid oxidation₃-RGO catalyst, this catalyst is to be prepared by following methods: take graphene oxide AMT(ammonium metatungstate mass concentration is 10%-30%) solution impregnates, Hydrothermal Synthesis processes and obtains WO₃-GO carrier, then Carry out potassium borohydride reduction method synthesis Pt-supported catalyst.

As preferably, described graphene oxide is to use Hummers method liquid phase oxidation synthesis.

As preferably, the mass concentration of AMT solution is 18-22%.

A kind of described Pd/WO for formic acid oxidation₃The preparation method of-RGO catalyst, the method includes walking as follows Rapid:

①WO₃The preparation of-GO carrier: AMT adds suitable quantity of water and dissolves, and then ultrasonic with graphene oxide mixs homogeneously, at 88-95 DEG C Lower insulation 6-8 hour, is cooled to room temperature, and reduce pressure sucking filtration, and washing is dried, 400-450 DEG C of roasting 4-5 h, obtained WO₃-GO carries Body；

2. the preparation of Pt-supported catalyst: WO₃-GO carrier mixes with suitable quantity of water, ultrasonic mix homogeneously, adds PdCl₂Solution, Make system heat up, in system, add the reducing agent KBH of excess when temperature reaches 50 ± 2 DEG C₄Solution, and nitrogen atmosphere, Condensing reflux under 50 DEG C of water-baths, maintains temperature to react at 50 ± 2 DEG C to fully, obtains Pd/WO after filtering drying₃-RGO is catalyzed Agent product.

As preferably, PdCl₂Addition for making Pd at Pd/WO₃Load capacity in-RGO catalyst is 15-25%.

The present invention carries out Hydrothermal Synthesis process and obtains loading WO graphene oxide and CNT₃Carrier, then at this base Carry out potassium borohydride reduction method synthesis Pt-supported catalyst on plinth, and study Pd/WO₃-RGO and Pd/WO₃-CNTs catalyst is to first Acid oxidase electrocatalysis characteristic, investigates the carrier impact on composite catalyst performance.Catalyst is carried out appearance structure sign, and grinds Study carefully the relation between catalyst surface pattern and microstructure and electrocatalysis characteristic.

The present invention, respectively with graphene oxide and CNT as raw material, uses hydrothermal synthesis method, it is thus achieved that WO₃-RGO with WO₃-CNTs carrier.Then potassium borohydride method is used to be prepared for Pd/WO respectively₃-RGO catalyst and Pd/WO₃-CNTs catalyst, And chemical property, the X-ray diffraction of catalyst is characterized with scanning electron microscope.And Study of Support is to composite catalyst performance Impact and the catalyst comparative study to formic acid oxidation electrocatalysis characteristic.Result shows, Pd/WO₃-RGO catalyst has Optimum chemical property and stability, and the catalyst performance of load Graphene is more preferable compared with CNT.Electro-chemical test is tied Fruit shows, uses WO on graphene oxide₃Modifying, its performance is better than the graphene oxide of unmodified, and the former has higher Hydrogen desorption electric current.SEM figure shows that on graphenic surface, Monodispersed Pd and WO₃Granule.The two is interlaced, creates and more has The synergism of profit.

Accompanying drawing explanation

Fig. 1 is electrochemical measurement three electrode cell structural representations；

Fig. 2 is different content Pd/WO₃-RGO and WO₃-GO catalyst and the XRD figure of graphene oxide；

Fig. 3 is that (a) (b) represents Pd/20%WO₃-RGO scanning electron microscope (SEM) photograph；C () (d) is Pd/20%WO₃-CNTs catalyst Scanning electron microscope (SEM) photograph；E () (f) represents Pd/20%WO respectively₃-RGO and Pd/20%WO₃Pd nano-particles size on-CNTs catalyst Scattergram；

Fig. 4 is Pd/20%WO₃-RGO and Pd/20%WO₃-CNTs catalyst electrode is at 0.5 mol/L H₂SO₄Following in electrolyte Ring volt-ampere curve, scanning speed is 50 mV/s；

Fig. 5 is Pd/20%WO₃-RGO and Pd/20%WO₃-CNTs catalyst electrode is at 1 mol L^-1 HCOOH + 0.5 mol· L^-1Cyclic voltammetry curve in electrolyte, scanning speed is 50 mV/s；

Fig. 6 is Pd/20%WO₃-RGO and Pd/20%WO₃-CNTs catalyst electrode is at 1 mol L^-1 HCOOH + 0.5 mol· L^-1 H₂SO₄Linear sweep voltammetry curve in electrolyte, scanning speed is 2 mV/s；

Fig. 7 is Pd/20%WO₃-RGO and Pd/20%WO₃-CNTs catalyst electrode current of polarization under 0.4 V constant potential is bent Line；

Fig. 8 is Pd/20%WO₃-RGO and Pd/20%WO₃-CNTs catalyst electrode is 4.8 mA cm in constant current density^-2's Time-measuring electric potential curve；

Fig. 9 is different content Pd/WO₃-RGO and 20%WO₃-GO catalyst electrode is at 0.5 mol/L H₂SO₄Following in electrolyte Ring volt-ampere curve；

Figure 10 is different content Pd/WO₃-RGO and 20%WO₃-GO catalyst electrode is at 1 mol L^-1 HCOOH + 0.5 mol·L^-1Cyclic voltammetry curve in electrolyte, scanning speed is 50 mV/s；

Figure 11 is different content Pd/WO₃-RGO and 20%WO₃-GO catalyst electrode is at 1 mol L^-1 HCOOH + 0.5 mol·L^-1 H₂SO₄Linear sweep voltammetry curve in electrolyte, scanning speed is 2 mV/s；

Figure 12 is different content Pd/WO₃-RGO catalyst electrode current of polarization curve under 0.4 V constant potential；

Figure 13 is different content Pd/WO₃-RGO catalyst electrode is 4.8 mA cm in constant current density^-2Time-measuring electric potential bent Line.

Detailed description of the invention

Below by specific embodiment, technical scheme is described in further detail.Should be appreciated that this Bright enforcement is not limited to the following examples, and any pro forma accommodation and/or the change of being made the present invention all will fall Enter scope.

In the present invention, if not refering in particular to, all of part, percentage ratio are unit of weight, the equipment used and raw material etc. All it is commercially available or commonly used in the art.Method in following embodiment, if no special instructions, is the normal of this area Rule method.

Key instrument Japan HITACHI H-700 type transmission electron microscope；XD-D1 type X of Shimadzu Shimadzu company of Japan is penetrated Line diffractometer；Air dry oven, DHG-9053AS；

Main agents Nafion, Anhui Rui Bang New Energy Technology Co., Ltd..

Embodiment 1:

1, the preparation of graphene oxide

Use Hummers method liquid phase oxidation synthesis graphene oxide.First the beaker filling 23 mL concentrated sulphuric acids is placed in ice-water bath In, add the graphite powder of 1 g, the ultrasonic 20 each 10min of min(), until in uniform state.Then 3 g permanganic acid it are slowly added into Potassium, ice-water bath is stirred continuously.After 2 h, ice bath completes, and is heated to 40 DEG C, reacts 40 min, and is slowly added into 50 mL distilled water. Add after end to 88 DEG C, and continuously stirred 1 h.Add 20 mL distilled water and 20 mL mass fractions are the H of 30%₂O₂.Then It is centrifuged while hot, is washed with distilled water to neutrality, be dried air dry oven 70 DEG C.

2, carrier is prepared

2.1 preparation 30%WO₃-GO

Weigh 8.5714 g AMT, 50 mL beakers add AMT and 20 mL distilled water, is stirred continuously and is allowed to be completely dissolved. Then the graphene oxide weighing 100 mg steps 1 prepared is put in beaker, each 10 min of ultrasonic 30 min(), until making it In uniform state.Then it is poured in reactor, puts in heating furnace, at 90 DEG C, be incubated 6 hours.Reaction terminates and cold But after, carrying out the sucking filtration that reduces pressure, wash by secondary deionized water, sucking filtration twice repeatedly, in drying baker 65 DEG C drying.By dried Sample be put in crucible furnace, at 400 DEG C of roasting 4 h of Muffle furnace.

2.2 preparation 30%WO₃-CNTs

Weigh 8.571g AMT, 50 mL beakers add AMT and 20 mL distilled water and is stirred continuously and is allowed to be completely dissolved.So Rear weighing 100 mg CNT is put in beaker, each 10 min of ultrasonic 30 min(), until making it is uniform state.Then It is poured in reactor, at 90 DEG C of heating furnace, is incubated 6 hours.After reaction terminates and cools down, carry out the sucking filtration that reduces pressure, with two Secondary deionized water wash, repeatedly sucking filtration twice.In drying baker 65 DEG C drying.Dried sample is put in crucible furnace, horse Not 400 DEG C of roasting 4 h of stove.

3, Pt-supported catalyst is prepared

3.1 preparation Pd/30%WO₃-RGO

Weigh 80 mg 30%WO₃-GO carrier, adds carrier and 30 mL distilled water in 50 mL beakers, and ultrasonic 30 min(are every Secondary 10 min) until making it is uniform state.Pipette 0.05 mol/LPdCl of 2.82 mL₂Solution, ultrasonic (20 min) is to complete Complete uniform.Then in three-neck flask, add this solution, water-bath carry out condensing reflux, set reaction temperature as 50 DEG C, Keep nitrogen atmosphere.KBH is prepared in beaker₄Solution (KBH₄253 mg, distilled water 60 mg).When the reaction temperature has been reached, use Needle tubing draws KBH₄Solution, keeps needle tubing drop by drop to instill in three-neck flask.Reaction carries out 6 h at 50 DEG C.Wait to terminate After, carry out filtered while hot, in drying baker 65 DEG C drying.

3.2 preparation Pd/30% WO₃-CNTs

Weigh 80 mg 30%WO₃-CNTs carrier, adds carrier and 30 mL distilled water, ultrasonic 30 min in 50 mL beakers (each 10 min) are until making it is uniform state.Measure 0.05 mol/LPdCl of 2.82 mL₂Solution, ultrasonic by Ultrasound Instrument (20 min) is to the most uniformly.Then in three-neck flask, add this solution, water-bath carries out condensing reflux, set reaction Temperature is 50 DEG C, keeps nitrogen atmosphere.KBH is prepared in beaker₄Solution (KBH₄253 mg, distilled water 60 mg).When reaching anti- When answering temperature, draw KBH with needle tubing₄Solution, keeps needle tubing drop by drop to instill in three-neck flask.Reaction is carried out at 50 DEG C 6 h.After terminating, carry out filtered while hot, in drying baker 65 DEG C drying.

The Pd/WO of 3.3 different contents₃Prepared by-RGO catalyst

Preparation 20%WO₃-GO and 10%WO₃-GO.Proportionally changing the consumption of AMT, preparation method and step are with 2.1.Pd/20% WO₃-RGO and Pd/10%WO₃The preparation process of-RGO is with 3.1.

The Pd/WO of 3.4 different contents₃Prepared by-CNTs catalyst

Preparation Pd/20%WO₃-CNTs and Pd/10%WO₃-CNTs.Proportionally changing the consumption of AMT, preparation method is same with step 2.2。Pd/20%WO₃-CNTs and Pd/10%WO₃The preparation process of-CNTs is with 3.2.

Embodiment 2:

1, the preparation of graphene oxide

Use Hummers method liquid phase oxidation synthesis graphene oxide.First the beaker filling 23 mL concentrated sulphuric acids is placed in ice-water bath In, add the graphite powder of 1 g, each 10min of ultrasonic 20min(), until in uniform state.Then 3 g permanganic acid it are slowly added into Potassium, ice-water bath is stirred continuously.After 2 h, ice bath completes, and is heated to 40 DEG C, reacts 40 min, and is slowly added into 50 mL distilled water. Add after end to 88 DEG C, and continuously stirred 1 h.Add 20 mL distilled water and 20 mL mass fractions are the H of 30%₂O₂.Then It is centrifuged while hot, is washed with distilled water to neutrality, be dried air dry oven 70 DEG C.

2 preparation WO₃-GO

Preparation mass concentration is the AMT(ammonium metatungstate of 20%) solution, it is subsequently adding the graphene oxide that 100 mg steps 1 prepare, Each 10 min of ultrasonic 30 min(), until making it is uniform state.Then it is poured in reactor, puts in heating furnace, It is incubated 6 hours at 90 DEG C.After reaction terminates and cools down, carry out the sucking filtration that reduces pressure, wash by secondary deionized water, sucking filtration repeatedly Twice, in drying baker 65 DEG C drying.Dried sample is put in crucible furnace, at 400 DEG C of roasting 4 h of Muffle furnace.

3 preparation Pd/WO₃-RGO

Weigh 80 mg WO₃-GO carrier, mixes with 30 mL distilled water, each 10 min of ultrasonic 30 min() until making it in all Even state.0.05 mol/LPdCl of 2.82 mL is pipetted in system₂Solution, ultrasonic (20 min) is to the most uniformly.At three necks Flask adds this solution, water-bath carries out condensing reflux, set reaction temperature as 50 DEG C, keep nitrogen atmosphere.Burning KBH is prepared in Bei₄Solution (KBH₄253 mg, distilled water 60 mg).When the reaction temperature has been reached, KBH is drawn with needle tubing₄Solution, Needle tubing is kept drop by drop to instill in three-neck flask.Reaction carries out 6 h at 50 DEG C.After terminating, carry out filtered while hot, Drying baker 65 DEG C drying.

Embodiment 3:

1, the preparation of graphene oxide

2 preparation WO₃-GO

Preparation mass concentration is the AMT(ammonium metatungstate of 10%) solution, it is subsequently adding the graphene oxide that 100 mg steps 1 prepare, Each 10 min of ultrasonic 30 min(), until making it is uniform state.Then it is poured in reactor, puts in heating furnace, It is incubated 6 hours at 90 DEG C.After reaction terminates and cools down, carry out the sucking filtration that reduces pressure, wash by secondary deionized water, sucking filtration repeatedly Twice, in drying baker 65 DEG C drying.Dried sample is put in crucible furnace, at 400 DEG C of roasting 4 h of Muffle furnace.

3 preparation Pd/WO₃-RGO

Embodiment catalyst performance is tested

The structural characterization of catalyst utilizes scanning electron microscope to carry out SEM test, by sample through ultrasonic, is scattered in ethanol.In standard Drip suspension on copper mesh, carry out transmission electron microscope observing.XRD test is carried out on XD-D1 type X-ray diffractometer, Cu target, A= 0.154056 nm。

The Electrochemical Characterization of catalyst and Experimental equipment

Electrochemical Characterization uses three-electrode system to carry out electrochemical property test, and three electrode cell structural representations are shown in Fig. 1, its In 1. pairs of electrodes；2. working electrode；3. reference electrode；4. glass membrane.Working electrode is homemade electrode, is platinum to electrode Sheet, reference electrode is saturated calomel electrode (SCE).Use cyclic voltammetry (CV), linear scanning method (LSV), chrono-amperometric And timing voltage (PVI) Study of Catalyst is to formic acid oxidation electrocatalysis characteristic (It).Concentration of electrolyte is 1 mol/L HCOOH+ 0.5 mol/L H₂SO₄, in electrolyte, first lead to N on pretreatment₂To remove molten O₂, duration of ventilation 20 min.

Prepared by working electrode

Weigh 5 mg catalyst, draw 15 μ L Nafion and 30 μ L dehydrated alcohol in bottle with microsyringe, with super Sound cleaning machine is ultrasonic, and making solution is uniform state.Use Al₂O₃After glass-carbon electrode is polished, the solution of the 2.5 μ L pipetted is applied to On it, after drying.

1 catalyst XRD test result analysis

Fig. 2 is different content Pd/WO₃-RGO and WO₃-GO catalyst and the XRD figure of GO, it can be seen that nethermost GO line is it can be seen that 2θBe about 11 ° place existence one C(002) strong diffraction maximum.But it is permissible with Pd/RGO COMPARATIVE CATALYST Find out that not this diffraction maximum on the same position on Pd/RGO catalyst shows to utilize potassium borohydride method by graphene oxide Reduce.After being reduced by graphene oxide, oxygen-containing functional group quantity thereon reduces, and graphene film interlamellar spacing reduces, this It is consistent with the change of XRD figure.It will be seen that the C(002 on Pd/RGO catalyst) strong diffraction maximum be moved rearwards by, 2θ? About 25 °.Show that the structure of Graphene there occurs that change, GO surface major part oxy radical are removed.For Pd/G catalyst, 2θBeing about 41 °, 45.7 °, 68.1 °, 81.2 °, corresponding with them is Pd crystal (111) respectively, (200), (220), (311) The diffraction maximum of crystal face, and diffraction maximum is 2θReach maximum at being about 41 °.Illustrate that Pd granule has been supported on above Graphene, And be face-centred cubic structure.WO at different content₃On-GO carrier, C(002) strong diffraction maximum be moved rearwards by equally, about 2θ It it is 24.8 °.The WO of different content₃The WO of-GO carrier₃Diffraction maximum the most mark, show to have been charged with on Graphene WO₃。 Similarly, different content Pd/WO₃The strongest diffraction maximum of Pd of-RGO catalyst is 2θAt being about 41 °, the diffraction maximum position of remaining Pd Consistent with Pd/RGO catalyst, WO₃Diffraction maximum identify the most in the drawings, show Pd/WO₃On the Graphene of-RGO catalyst Load P d and WO₃。

2 catalyst SEM test result analysis

Fig. 3 (a) (b) is Pd/20%WO₃The scanning electron microscope (SEM) photograph of-RGO catalyst, and Fig. 3 (c) (d) is Pd/20%WO₃- The scanning electron microscope (SEM) photograph of CNTs catalyst.Can be seen that Pd/20%WO₃-RGO catalyst and Pd/20%WO₃All occur in that on-CNTs Erose WO₃Granule and spherical Pd granule, and Pd granule is evenly dispersed in carrier Tungstic anhydride ./Graphene and three On tungsten oxide/carbon nanotube.

Fig. 3 (e) and 3 (f) are respectively Pd/20%WO₃-RGO and Pd/20%WO₃Pd nano-particles size on-CNTs catalyst Scattergram.Pd/20%WO₃Mean diameter 8.6 nm of Pd granule, particle size range 5-13 nm, and Pd/20% on-CNTs catalyst WO₃Mean diameter 7.0 nm of Pd granule on-RGO catalyst, particle size range is 3-11 nm.This shows Pt/20%WO₃-RGO urges In agent, the mean diameter of Pd nanoparticle is less, and the dispersibility on carrier is more preferable.

The chemical property of 3 catalyst electrodes compares

3.1 at H₂SO₄Pd/20%WO in system₃-RGO and Pd/20%WO₃The chemical property contrast of-CNTs catalyst

Fig. 4 represents Pd/RGO, Pd/CNTs, Pd/20%WO₃-RGO and Pd/20%WO₃-CNTs catalyst electrode is at 0.5 mol/L H₂SO₄Cyclic voltammetry curve in solution.According to figure it can be seen that these four catalyst are respectively provided with obvious hydrogen desorption peak, just The electrochemical active surface of catalyst electrode is evaluated according to this area.With do not carry WO₃Catalyst (Pd/RGO or Pd/ CNTs) compare, be loaded with WO₃(Pd/20%WO₃-RGO or Pd/20%WO₃-CNTs) catalyst corresponding thereto has higher hydrogen Desorption electric current, possible cause is WO₃Create more favourable synergism with Pd, show to carry WO₃Make the electro-chemical activity of catalyst Area increases.It can also be seen that Pd/20%WO from figure₃The hydrogen desorption peak current relatively Pd/20%WO of-RGO₃-CNTs electric current is big, but It is that hydrogen desorption peak area is more or less the same.From the contrast of RGO Yu CNTs cyclic curve it can be seen that the catalyst with RGO as carrier is electric The hydrogen desorption oxidation current of pole is more than the hydrogen desorption oxidation current of the catalyst with CNTs as carrier, and possible cause is Graphene tool There are bigger specific surface area and good electric conductivity.

3.2 at H₂SO₄Pd/20%WO in+HCOOH system₃-RGO and Pd/20%WO₃The chemical property of-CNTs catalyst Contrast

Fig. 6 is Pd/RGO, Pd/CNTs, Pd/20%WO₃-RGO and Pd/20%WO₃-CNTs catalyst electrode is at 0.5 mol/L H₂SO₄With the cyclic voltammetry curve in 1 mol/L HCOOH solution.Following information can be obtained: each catalyst represents from figure Cyclic voltammetry curve all have oxidation peak, and size of current is arranged as from big to small: Pd/20%WO₃-RGO > Pd/20%WO₃- CNTs > Pd/RGO > Pd/CNTs.And the peak produced substantially close to, be near 0.27V.Load is may indicate that from this Body has considerable influence to formic acid oxidation current peak, little on the impact of spike potential value on the contrary.Contrast Pd/20%WO₃-RGO with Pd/RGO is it can be seen that owing to being loaded with WO₃Relation so that oxidation current peaks is higher, shows WO₃Catalyst can be made to show Preferably formic acid electrocatalytic oxidation property.Contrast Pd/20%WO₃-RGO and Pd/20%WO₃-CNTs catalyst is it can be seen that Pd/ 20%WO₃-RGO has more preferable formic acid oxidation electro catalytic activity, show carrier Graphene compared with CNTs, Graphene has more Carrier effect.Because Graphene has bigger specific surface area, it is possible to adsorb more Pd, thus improve the catalysis of catalyst Activity, shows the oxidation current peaks more increased.

Fig. 5 represents Pd/RGO, Pd/CNTs, Pd/20%WO₃-RGO and Pd/20%WO₃-CNTs catalyst electrode is 0.5 mol/L H₂SO₄With the 1 mol/LHCOOH solution linear sweep voltammetry curve to formic acid oxidation, conclusion and cyclic voltammetry curve one Sample.

3.3 Pd/20%WO₃-RGO and Pd/20%WO₃-CNTs catalyst stability contrasts

In order to investigate Pd/20%WO₃-RGO and Pd/20%WO₃The stability of-CNTs catalyst electrode and the contrast feelings of the two Condition, we under 0.4V constant potential, two electrodes have been carried out current of polarization curve test, experimental result is as shown in Figure 7.From figure In we can obtain: four catalyst agent are in the starting stage, and electric current density is all in the tendency drastically fallen, the most gradually Start to slow down.In whole test process, the formic acid oxidation electric current density of catalyst the most successively: Pd/20%WO₃- RGO, Pd/20%WO₃-CNTs, Pd/RGO and Pd/CNTs.Thus Pd/20%WO is described₃The optimal stability of-RGO.

At 4.8 mA/cm²In constant current density, Pd/RGO, Pd/CNTs, Pd/20%WO₃-RGO and Pd/20%WO₃- The CNTs catalyst electrode time-measuring electric potential curve to formic acid oxidation, result is as shown in Figure 8.From the figure, it can be seen that Pd/20% WO₃-RGO, Pd/20%WO₃-CNTs, Pd/RGO catalyst is in test process, and curve is stable, and current potential upstroke slope is more slow, and Pd/CNTs catalyst electrode is equally relatively slower in the starting stage, but at about 1700s, jumps suddenly, and current potential rises suddenly Height, becomes mild again after terminating to test.Contrast Pd/20%WO again₃-RGO, Pd/20%WO₃-CNTs, Pd/RGO tri-catalysis Agent is it is recognised that Pd/20%WO₃-RGO is in about-0.2V, and current potential negative value is maximum.Because the negative pole of aminic acid fuel battery is sent out Raw is formic acid oxidation reaction, so current potential negative value is the biggest, the performance of fuel cell is more preferably.Compare CNTs supported catalyst, RGO Supported catalyst has more preferable catalyst stability.Illustrate that Graphene is as carrier, it is possible to more adsorb Pd, it is thus possible to Enough improve the catalysis activity of the stability of catalyst and the oxidation reaction of formic acid.

The Pd/WO of 3.4 different contents₃-RGO chemical property contrasts

For relatively different WO₃The Pd/WO of percentage composition₃The chemical property of-RGO catalyst and the catalyst of optimum, again To Pd/10%WO₃-RGO、Pd/20%WO₃-RGO、Pd/30%WO₃-RGO and Pd/RGO carries out electrocatalysis characteristic test.

1. at H₂SO₄The chemical property of catalyst under system

Fig. 9 is at 0.5 mol/L H₂SO₄In electrolyte, different content Pd/WO₃-RGO and 20%WO₃-GO catalyst electrode Cyclic voltammetry curve, sweeps speed for 50mV/s.Understand according to figure, the Pd/WO of different content₃-RGO catalyst is respectively provided with higher Hydrogen desorption oxidation peak.Wherein it is loaded with WO₃Catalyst peak current be above Pd/RGO.Although Pd/30%WO₃-RGO and Pd/10% WO₃The hydrogen desorption area of-RGO is very nearly the same, but the former peak current is slightly larger.It can be seen that explanation WO₃Content be not the highest The best, but there is an optimal amount.Through WO₃Modified catalyst also electric current compared with pure Pd/RGO is big, shows to load WO₃Make The electrochemical surface area of catalyst increases.Contrast Pd/xWO₃-RGO and 20%WO₃-GO understands, and obtains through potassium borohydride reduction Pt-supported catalyst there is higher oxidation peak peak value and electric current density.Graphene after illustrating with reduction is carrier loaded Pd, it is possible to adsorb more Pd granule, promotes the performance of catalyst further.

2. at H₂SO₄The chemical property of catalyst under+HCOOH system

Figure 10 is different content Pd/WO₃-RGO catalyst electrode is at 1 mol L^-1 HCOOH + 0.5 mol·L^-1Electrolyte In cyclic voltammetry curve, scanning speed is 50 mV/s.Understand: in whole process of the test, the circulation that every kind of catalyst is done Volt-ampere curve all has oxidation peak, and electric current presses Pd/20%WO₃-RGO> Pd/30%WO₃-RGO> Pd/10%WO₃-RGO's > Pd/RGO Order is sequentially reduced.But produce peak substantially close to, be near 0.19V.May indicate that carrier is to first from this Acid oxidase current peak has considerable influence, little on the impact of spike potential value on the contrary.Contrast Pd/20%WO₃-RGO and Pd/RGO It can be seen that owing to being loaded with WO₃Relation so that oxidation current peaks is higher, shows WO₃Catalyst can be made to show preferably Formic acid electrocatalytic oxidation property.Therefrom it can also be seen that WO₃Content there is optimal amount.Equally, the different WO of contrast₃Content Pd/ WO₃-RGO and carrier WO₃-GO understands, and the Pt-supported catalyst obtained through potassium borohydride reduction has higher oxidation peak peak value With electric current density.Graphene after illustrating with reduction is carrier loaded Pd, it is possible to adsorb more Pd granule, promotes further and urges The performance of agent.

Figure 11 Pd/WO₃-RGO catalyst electrode is at 1 mol L^-1 HCOOH + 0.5 mol·L^-1 H₂SO₄Electrolyte In linear sweep voltammetry curve, scanning speed is 2 mV/s.Its conclusion is as cyclic voltammetry curve.

3. catalyst stability test

Under 0.4V constant potential, catalyst electrode is carried out the test of current of polarization curve, the Pd/WO of test different content₃- The stability of RGO Catalysts for Electrocatalytic Oxidation formic acid, as shown in figure 12.In whole test process, all catalyst are initially Stage all shows identical trend, i.e. in the electric current density the most linearly downward trend of starting stage, after a period of time, opens Beginning tends towards stability.Whole result shows, electric current density: Pd/20%WO₃-RGO> Pd/30%WO₃-RGO> Pd/10%WO₃-RGO> Pd/RGO, reduces successively.During testing current, Pd/20%WO₃The electric current density of-RGO catalyst is constantly in highest point, and Highest current density.Pd/20%WO is described₃The optimal stability of-RGO catalyst.

At constant 4.8 mA cm^-2Under electric current density, different content Pd/WO₃-RGO catalyst electrode is for formic acid oxidation Time-measuring electric potential curve as shown in figure 13.In test process, all catalyst are respectively provided with the trend risen.Compare it His three catalyst, Pd/20%WO₃The ascendant trend ratio of-RGO catalyst is shallower.And Pd/20%WO₃The negative value of-RGO is always It is in the position of maximum.Because the negative pole of aminic acid fuel battery happens is that formic acid oxidation reacts, so current potential negative value is the biggest, combustion The performance of material battery is more preferably.Therefore, Pd/20%WO₃The stability of-RGO catalyst is the highest.For Pd/RGO catalyst, in experiment When carrying out about 500s, there is the process of obvious rise and fall, and at about 1500s, have again one to decline and rising Process, shows not to be especially good with the stability of catalyst in mid-term in the early stage.Come from the experimental results, WO is described equally₃Contain Amount is not the highest more good, but there is an optimum content.A certain amount of Pd and WO₃Produce synergism, can be further Promote performance and the stability of catalyst.

To sum up, the present invention is by utilizing WO₃-GO and WO₃-CNTs is as carrier, then carries out potassium borohydride method preparation the most on year-on-year basis The Pd/WO of example₃-RGO and Pd/WO₃-CNTs catalyst.Thus study the two and to the difference of formic acid oxidation performance and consider Different WO₃The impact of content.In this test, it is concluded that as follows: 1) on carrier, utilize WO₃Modifying, its performance is better than The carrier of unmodified；2) catalyst performance with RGO as load carriers is better than the catalyst with CNTs as load carriers；3) different Content WO₃Pd/WO₃In-RGO COMPARATIVE CATALYST, Pd/20%WO₃-RGO catalyst have optimum electrochemical catalysis performance with Stability.

Electrochemical results shows, uses WO on graphene oxide₃Modifying, its performance is better than the oxidation of unmodified Graphene, the former has higher hydrogen desorption electric current.SEM figure shows that on graphenic surface, Monodispersed Pd and WO₃Granule.The two Interlaced, create more favourable synergism.

Pd/20%WO₃-RGO catalyst has optimal formic acid oxidation catalysis activity and stability, Pd/20%WO₃-RGO with Pd/RGO compares, due to load WO₃, WO₃Create more favourable synergism with Pd, improve catalyst catalysis activity with Stability.In addition, potentiostatic polarization curve and constant current discharge curve show Pd/20%WO₃-RGO has stablizing of excellence Property.The Pd/20%WO of different content₃The chemical property result of-RGO catalyst represents, WO₃Content there is optimal amount.

Pd/20%WO₃-RGO catalyst and Pd/20%WO₃-CNTs catalyst is compared, Pd/20%WO₃-RGO has preferably Stability, higher formic acid oxidation electric current density, more preferable catalyst stability.Because Graphene is bigger than CNT has Specific surface area, beneficially Pd is in the dispersion on its surface, thus improves the utilization rate of Pd, strengthen catalyst catalytic performance.

Embodiment described above is the one preferably scheme of the present invention, not makees the present invention any pro forma Limit, on the premise of without departing from the technical scheme described in claim, also have other variant and remodeling.

Claims

1. the Pd/WO for formic acid oxidation₃-RGO catalyst, it is characterised in that: this catalyst is to be prepared by following methods: Take graphene oxide at the AMT(ammonium metatungstate that mass concentration is 10%-30%) solution impregnates, Hydrothermal Synthesis processes and obtains WO₃- GO carrier, then carries out potassium borohydride reduction method synthesis Pt-supported catalyst.

Pd/WO for formic acid oxidation the most according to claim 1₃-RGO catalyst, it is characterised in that: described oxidation Graphene is to use Hummers method liquid phase oxidation synthesis.

Pd/WO for formic acid oxidation the most according to claim 1₃-RGO catalyst, it is characterised in that: the matter of AMT solution Amount concentration is 18-22%.

4. the Pd/WO for formic acid oxidation described in a claim 1₃The preparation method of-RGO catalyst, it is characterised in that should Method comprises the steps:

2. the preparation of Pt-supported catalyst: WO₃-GO carrier mixes with suitable quantity of water, ultrasonic mix homogeneously, adds PdCl₂Solution, makes System heats up, and adds the reducing agent KBH of excess in system when temperature reaches 50 ± 2 DEG C₄Solution, and nitrogen atmosphere, 50 Condensing reflux under DEG C water-bath, maintains temperature to react at 50 ± 2 DEG C to fully, obtains Pd/WO after filtering drying₃-RGO catalyst Product.

Preparation method the most according to claim 4, it is characterised in that: PdCl₂Addition for making Pd at Pd/WO₃-RGO urges Load capacity in agent is 15-25%.