CN113373472A

CN113373472A - Polypyrrole/rhodium nanoparticle composite flexible electrode and preparation method and application thereof

Info

Publication number: CN113373472A
Application number: CN202110666724.XA
Authority: CN
Inventors: 张欣; 杨逢春; 李天天
Original assignee: Northwestern University
Current assignee: Northwestern University
Priority date: 2021-06-16
Filing date: 2021-06-16
Publication date: 2021-09-10
Anticipated expiration: 2041-06-16
Also published as: CN113373472B

Abstract

The invention belongs to the technical field of electrode materials, and particularly relates to a polypyrrole/rhodium nanoparticle composite flexible electrode as well as a preparation method and an application thereof.

Description

Polypyrrole/rhodium nanoparticle composite flexible electrode and preparation method and application thereof

Technical Field

The invention belongs to the technical field of electrode materials, and particularly relates to a polypyrrole/rhodium nanoparticle composite flexible electrode as well as a preparation method and application thereof.

Background

Electrochemical hydrogen production is a key of many renewable energy systems, particularly hydrogen production by water cracking, and in water cracking, an ideal electrode is a flexible self-supporting catalytic material because: the self-supporting electrode has larger surface area, is also favorable for discharging bubbles generated by catalysis in time in the catalysis process and is favorable for the continuous generation of reaction.

The catalysts commonly used in the prior art are nano inorganic materials, and although the catalysts have good catalytic performance, the catalysts cannot be used as independent flexible electrodes, which limits the application of the catalysts in water cracking.

The conventional electrodes mainly comprise a glassy carbon electrode, Carbon Cloth (CC) and the like, and the glassy carbon electrode is expensive, easy to pollute in the using process and not suitable for water cracking; the carbon cloth has the characteristic of flexibility, but the carbon cloth is expensive, complex pretreatment steps are required before use, and the carbon cloth has certain limitation in practical application, so that the preparation of a self-supporting and flexible electrode becomes a new direction for researching the electrocatalyst; in recent years, documents report that polymers are combined with inorganic materials and widely applied to various flexible apparatuses, such as batteries, electrical detection and capacitors, and this shows that the good mechanical properties of the polymers can make up for the defects of inorganic nano materials, so that flexible self-supporting electrodes with good catalytic properties are obtained.

Conductive polymers, such as poly 3, 4-ethylenedioxythiophene monomers: polystyrene sulfonate (PEDOT-PSS), Polyaniline (PANI), polypyrrole (PPy) and the like are widely applied to the electrochemical field because conductive polymers have good mechanical properties and conductivity, and particularly polypyrrole is widely concerned as a high polymer material which is cheap in raw materials, simple in preparation method, good in conductivity and easy to form a film; polypyrrole is generally synthesized by a chemical oxidation method or an electrodeposition method, wherein the chemical oxidation method generally obtains powdery PPy, and the electrodeposition method can obtain a flexible independent PPy film; however, PPy, although having good mechanical properties, does not itself have a rich number of electrocatalytic active sites, and when it is applied in electrochemical materials, especially in electrocatalytic processes, it is difficult to overcome the slow kinetics of hydrogen evolution and oxygen evolution.

In the electrochemical hydrogen evolution process, Pt and Pt-based materials are the best known hydrogen production materials at present, however, the scarcity of Pt limits the further development of the Pt; it is therefore critical to find an alternative catalytic material. In recent years, reports on Rh-based materials have also shown that Rh has good HER catalytic performance and stability enough to be comparable to Pt, however, Rh, as an inorganic material, has poor mechanical properties that further limit its development in electrocatalytic water splitting.

Disclosure of Invention

Aiming at the technical defects, the invention provides a polypyrrole/rhodium nanoparticle composite flexible electrode as well as a preparation method and application thereof.

In order to solve the technical problem, the utility model adopts the following technical scheme:

the preparation method of the polypyrrole/rhodium nanoparticle composite flexible electrode comprises the following steps:

(1) cleaning and cutting the ITO conductive glass;

(2) preparing a polypyrrole/rhodium nanoparticle composite flexible electrode:

s1, dissolving rhodium chloride monohydrate in deionized water to prepare a solution of 0.01-0.05mol/L, and then adding sulfuric acid and pyrrole to prepare a mixed solution;

wherein the mass ratio of the rhodium chloride monohydrate, the sulfuric acid and the pyrrole is 1: 2-5;

s2, taking the Ag/AgCl electrode as a reference electrode, a platinum wire electrode as a counter electrode and ITO conductive glass as a working electrode to form a three-electrode system, taking the mixed solution obtained in the step S1 as a deposition solution, and depositing pyrrole and rhodium on the surface of the working electrode by adopting a multi-potential alternative deposition method to prepare the polypyrrole/rhodium nanoparticle composite flexible electrode;

the multi-potential alternative deposition method comprises the following specific steps: the working electrode is alternately placed under the potential condition of 0.8-1V for depositing for 20s and-0.6-0.4V for depositing for 10s, and the deposition operation is alternately performed for 150-500 s.

Preferably, the total deposition time of the step S2 is 300-400S.

Preferably, the multi-potential alternating deposition method of step S2 includes the following specific steps: the working electrode is deposited for 20s under the condition of 0.8V potential, then the deposition is continued for 10s under the condition of-0.5V potential, and the deposition sequence is alternated to deposit for 350 s.

Preferably, the method for cleaning the ITO conductive glass in step (1) comprises: h with the mass fraction of 70 percent is adopted in sequence₂SO₄And washing the ITO glass for 10-20min by using deionized water and acetone, and drying.

Preferably, the washed ITO conductive glass is cut to be (1-3) × (2-3) cm in the step (1)²。

The invention also protects the polypyrrole/rhodium nanoparticle composite flexible electrode prepared by the preparation method.

The invention also protects the application of the polypyrrole/rhodium nanoparticle composite flexible electrode in the preparation of an electrolytic water catalytic electrode.

Preferably, the method for water electrolysis catalytic reaction comprises the following steps: and (2) taking an Ag/AgCl electrode containing saturated potassium chloride as a reference electrode, taking a platinum wire electrode as a counter electrode, forming a three-electrode system with the polypyrrole/rhodium nanoparticle composite flexible electrode as a working electrode, connecting the three-electrode system to electrochemical detection equipment, and electrolyzing by taking a sulfuric acid solution with the pH value of 0.2-1 as an electrolyte.

Compared with the prior art, the invention has the beneficial effects that:

1. the invention prepares polypyrrole (PPy) by oxidizing pyrrole at 0.8-1V through an electrodeposition method, and reduces Rh at-0.6-0.4V³⁺Rh is obtained, providing a high catalysis of rhodiumThe electrode material effectively combines the activity and the mechanical property of polypyrrole.

2. The invention adopts a multi-potential alternate deposition method (multi-potential steps) to prepare PPy/Rh composite material, and obtains the optimal deposition time by optimizing the deposition time of Rh and PPy; and further, the electron transfer condition between Rh and PPy is researched through characterization tests, and the fact that a large number of electron delocalized centers can be generated after the Rh and the PPy are compounded is proved, and the electron delocalized centers can be used as sites for generating rich catalytic activity in an electrocatalysis process.

3. Electrochemical tests demonstrated that in an acid electrolyte, PPy/Rh formed at a deposition time of 350s₃₅₀Only 59.5mV is needed to reach HER 10mA cm^-2Has a low Tafel slope (58.78mV dec)^-1) And, in addition, each at 10mA · cm^-2And 20mA · cm^-2Also the excellent stability was demonstrated by i-t testing at constant current for up to 24 h.

4. Compared with the traditional catalytic material, the polypyrrole/rhodium nanoparticle composite flexible electrode is used as an independent self-supporting electrode, and has the advantages that the preparation method is simple and quick, the preparation of the electrode can be completed within a few minutes, the performance is excellent and stable, and the loading capacity of the precious metal Rh is extremely low, so that the raw material is saved to the greatest extent; meanwhile, the flexible electrode can still maintain the electrochemical performance before bending after bending and folding, which provides a good starting point for the application of the flexible electrode in chemical devices.

Drawings

FIG. 1 is a schematic diagram of the preparation process of the polypyrrole/rhodium nanoparticle composite flexible electrode of examples 1 to 7 of the invention;

FIG. 2 shows Rh/PPy obtained in example 1 of the present invention₃₅₀I-t curve of deposition process;

FIG. 3 shows Rh/PPy from example 1 peeled off after immersion in hot water₃₅₀An optical picture of the film;

FIG. 4 shows Rh/PPy obtained in example 1 of the present invention₃₅₀Gel permeation chromatogram of (1);

FIG. 5 shows Rh obtained in comparative example 3 and Rh obtained in comparative example 2PPy and Rh/PPy from example 1₃₅₀Scanning electron microscope SEM image of (1);

in fig. 5, a is an SEM image of Rh prepared in comparative example 3; b is an SEM image of the PPy film prepared in comparative example 2; c is Rh/PPy from example 1_350sSEM picture of (1);

FIG. 6 is SEM topographies of polypyrrole/rhodium nanoparticle composite flexible electrodes at different deposition times for examples 4-7;

in FIG. 6, a is Rh/PPy of example 4₅₅A drawing; b is Rh/PPy from example 5₁₅₀A drawing; c is Rh/PPy of example 6₂₄₀(ii) a d is Rh/PPy from example 7₅₀₀；

FIG. 7 shows Rh from comparative example 3 and Rh/PPy from example 1_350sXRD map of (1);

FIG. 8 is an XRD spectrum of PPy obtained in comparative example 2;

FIG. 9 shows PPy obtained in comparative example 2 and Rh/PPy obtained in example 1_350sA raman contrast map of;

FIG. 10 is a Raman spectrum of Rh/PPy at different deposition times;

FIG. 11 is an XPS spectrum of Rh 3 d;

in FIG. 11, a is Rh obtained in comparative example 3 and Rh/PPy obtained in example 1_350sNarrow spectrum of Rh 3 d; b is the Rh 3d narrow spectrum of Rh/PPy at different deposition times obtained in example 1, examples 4-7; c is PPy obtained in comparative example 2 and Rh/PPy obtained in example 1_350sNarrow spectrum of N1 s; d is the N1s narrow spectrum of Rh/PPy at different deposition times obtained in example 1 and examples 4-7;

in FIG. 12, a is Rh/PPy obtained in example 1_350sRh from comparative example 3, Pt/C from comparative example 1 at 0.5mol of H₂SO₄HER polarization curve in (1); b is a Tafel slope diagram corresponding to a;

in FIG. 13, a is H at 0.5mol of Rh/PPy obtained in examples 1 and 4-7 at different deposition times₂SO₄HER polarization curve in (1); b is a Tafel slope diagram corresponding to a;

in FIG. 14, a is Rh/PPy obtained in example 1_350sRh and p from comparative example 3Electrochemical impedance spectrum of Pt/C of proportion 1; b is electrochemical impedance spectra of Rh/PPy obtained in example 1 and examples 4-7 at different deposition times;

FIG. 15 shows different materials vs. 0.5mol H₂SO₄Contact angle test chart of (1);

in FIG. 15, a is the PPy of comparative example 2; b is Rh/PPy from example 4_55s(ii) a c is Rh/PPy of example 5_150s(ii) a d is Rh/PPy from example 6_240s(ii) a e is Rh/PPy of example 1_350s(ii) a f is Rh/PPy from example 7_500s；

In FIG. 16, a is a current density of 10mA cm or less^-2And 20mA cm^-2Rh/PPy_350sI-t test curve of (1); b is Rh/PPy_350sComparison of LSV curves before and after 5000 cyclic voltammetric scans, the panels inserted in b are CV comparisons at the first and 5000 th cycles;

in FIG. 17, a is Rh/PPy_350s//RuO₂And Pt// RuO₂The polarization curve of water splitting of (1); b is Rh/PPy// RuO₂The two-electrode system has a current density of 10mA cm^-2The following i-t test curve graph;

in fig. 18, bending is performed by a; b, curling; Rh/PPy from example 1 with c-twist and d-fold_350sA real object diagram;

in FIG. 19, a is Rh/PPy before and after bending_350sA plot of HER polarization for the films; b is a Tafel slope diagram corresponding to a.

Detailed Description

The following detailed description of specific embodiments of the invention is provided, but it should be understood that the scope of the invention is not limited to the specific embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention. The experimental methods described in the examples of the present invention are all conventional methods unless otherwise specified.

TABLE 1 Experimental apparatus

Laboratory apparatus	Model number	Manufacturer of the product
			Electronic analytical balance	AR224CN	Shanghai Oxx instruments Ltd
Vacuum drying oven	DHG-9076A	Shanghai Jinghong experiment equipment Co Ltd
			Ultrasonic cleaning machine	KQ-100E	KUNSHAN ULTRASONIC INSTRUMENTS Co.,Ltd.
Centrifugal machine	TG16-WS	HUNAN XIANGYI LABORATORY INSTRUMENTS DEVELOPMENT Co.,Ltd.
			Fourier infrared spectrometer	TENSOR27	Bruker，German
X-ray powder diffractometer	D8 ADVANCE	Bruker，German
			Raman spectrum	HR	800	Hormonal，USA
X-ray photoelectron spectroscopy	5000VersaProbe	PHI，Japan
			Scanning electron microscope	SU-8010	HITACHICo.Ltd.，Japan
Electrochemical workstation	CHI660E	Shanghai Chenghua Instrument Co., Ltd

The main reagents required for the experiment are shown in table 2:

TABLE 2 test reagents

Chemical reagent	Specification of	Manufacturer of the product
			Rhodium chloride monohydrate	99％	SHANGHAI ALADDIN BIOCHEMICAL TECHNOLOGY Co.,Ltd.
Concentrated sulfuric acid	Analytical purity	Tianjin chemical reagent Co Ltd
			Azole compounds	0.968-0.971g/mL,≥98％	Shanghai Kewang industries Ltd
Acetone (II)	≥99.5％	Tianjin Lianlong Bohua pharmaceutical chemistry, Inc
			Nickel acetate	Analytical purity	Shanghai Zhanyun chemical Co Ltd
Anhydrous ethanol	Analytical purity	Tianjin chemical reagent Co Ltd
			Ultrapure water	Milli-Q pure water purification system	Millipore, USA

Example 1

(1) cleaning and cutting the ITO conductive glass;

h with the mass fraction of 70 percent is adopted in sequence₂SO₄Washing the ITO glass for 20min by using the solution, deionized water and acetone, and drying; cutting the cleaned ITO conductive glass to 1cm multiplied by 2 cm;

(2) preparing a polypyrrole/rhodium nanoparticle composite flexible electrode:

s1, dissolving rhodium chloride monohydrate in deionized water to prepare a 0.01mol/L solution, and then adding 0.01mol of sulfuric acid and 0.02mol of pyrrole to prepare a mixed solution;

the multi-potential alternative deposition method comprises the following specific steps: depositing the working electrode for 20s under the condition that the potential is 0.8V, then continuously depositing for 10s under the condition that the potential is minus 0.5V, alternately operating according to the deposition sequence, and codepositing for 350s to prepare the polypyrrole/rhodium nanoparticle composite flexible electrode (PPy/Rh)_350s)。

The method for the electrolytic water catalytic reaction comprises the following steps:

and (2) forming a three-electrode system by taking an Ag/AgCl electrode containing saturated potassium chloride as a reference electrode, a platinum wire electrode as a counter electrode and the prepared polypyrrole/rhodium nanoparticle composite flexible electrode as a working electrode, connecting the three-electrode system to electrochemical detection equipment, taking 0.5mol of sulfuric acid solution as electrolyte, and drawing a working curve by adopting a cyclic voltammetry method and a linear scanning voltammetry method.

Example 2

(1) cleaning and cutting the ITO conductive glass;

h with the mass fraction of 70 percent is adopted in sequence₂SO₄Washing the ITO glass for 10min by using the solution, deionized water and acetone, and drying; cutting the cleaned ITO conductive glass to 2cm multiplied by 2 cm;

(2) preparing a polypyrrole/rhodium nanoparticle composite flexible electrode:

s1, dissolving rhodium chloride monohydrate in deionized water to prepare a 0.03mol/L solution, and then adding 0.03mol of sulfuric acid and 0.1mol of pyrrole to prepare a mixed solution;

the multi-potential alternative deposition method comprises the following specific steps: and depositing the working electrode for 20s under the condition that the potential is 0.9V, then continuously depositing for 10s under the condition that the potential is-0.4V, and alternately operating according to the deposition sequence to co-deposit for 500s to prepare the polypyrrole/rhodium nanoparticle composite flexible electrode.

Example 3

(1) cleaning and cutting the ITO conductive glass;

h with the mass fraction of 70 percent is adopted in sequence₂SO₄Washing the ITO glass for 20min by using the solution, deionized water and acetone, and drying; cutting the cleaned ITO conductive glass to 3cm multiplied by 3 cm;

(2) preparing a polypyrrole/rhodium nanoparticle composite flexible electrode:

s1, dissolving rhodium chloride monohydrate in deionized water to prepare a 0.05mol/L solution, and then adding 0.05mol of sulfuric acid and 0.25mol of pyrrole to prepare a mixed solution;

the multi-potential alternative deposition method comprises the following specific steps: and depositing the working electrode for 20s under the condition that the potential is 1.0V, then continuously depositing for 10s under the condition that the potential is-0.6V, and performing alternate operation according to the deposition sequence to codeposit for 350s to obtain the polypyrrole/rhodium nanoparticle composite flexible electrode.

Example 4

The same procedure as in example 1, except that the co-deposition time was changed from 350s to 55s, was used to fabricate a polypyrrole/rhodium nanoparticle composite flexible electrode (PPy/Rh)_55s)。

the same procedure as in example 1 was followed except that the PPy/Rh prepared in example 1 was used_350sReplacement by PPy/Rh_55sAs a working electrode.

Example 5

The same procedure as in example 1 was followed, except that the codeposition time was changed from 350s to 150s (PPy/Rh)_150s)。

the same procedure as in example 1 was followed except that the PPy/Rh prepared in example 1 was used_350sReplacement by PPy/Rh_150sAs a working electrode.

Example 6

The same procedure as in example 1 was followed, except that the codeposition time was changed from 350s to 240s (PPy/Rh)_240s) As a working electrode.

the same procedure as in example 1 was followed except that the PPy/Rh prepared in example 1 was used_350sReplacement by PPy/Rh_240sAs a working electrode.

Example 7

The same procedure as in example 1 was followed, except that the codeposition time was changed from 350s to 500s (PPy/Rh)_500s) As a working electrode.

the same procedure as in example 1 was followed except that the PPy/Rh prepared in example 1 was used_350sReplacement by PPy/Rh_500sAs a working electrode.

In the following, the polypyrrole/rhodium nanoparticle composite flexible electrodes prepared in examples 1 and 4 to 7 are taken as examples for research, and the polypyrrole/rhodium nanoparticle composite flexible electrodes prepared in examples 1 and 4 to 7 are taken as working electrodes, and the specific research methods and research results are as follows:

comparative example 1

The polypyrrole/rhodium nanoparticle composite flexible electrode prepared in example 1 as the working electrode was replaced with an industrialized Pt/C electrode, and a working curve was drawn by cyclic voltammetry and linear sweep voltammetry.

Comparative example 2

Preparation of PPy:

(1) cleaning and cutting the ITO conductive glass;

(2) preparation of polypyrrole:

and S2, taking an Ag/AgCl electrode as a reference electrode, a platinum wire electrode as a counter electrode and ITO conductive glass as a working electrode to form a three-electrode system, taking the mixed solution prepared in the step (2) as a deposition solution, depositing for 100S under the condition that the potential is 0.8V, placing the working electrode in hot water, and stripping polypyrrole from the ITO conductive glass to prepare polypyrrole (PPy).

the same procedure as in example 1 was followed except that the PPy/Rh prepared in example 1 was used_350sPPy was substituted for the working electrode.

Comparative example 3

Preparation of Rh:

(1) cleaning and cutting the ITO conductive glass;

h with the mass fraction of 70 percent is adopted in sequence₂SO₄Solution, deionizationWashing the ITO glass with water and acetone for 20min, and drying; cutting the cleaned ITO conductive glass to 1cm multiplied by 2 cm;

(2) preparation of rhodium:

and S2, taking the Ag/AgCl electrode as a reference electrode, a platinum wire electrode as a counter electrode and ITO conductive glass as a working electrode to form a three-electrode system, taking the mixed solution prepared in the step (2) as a deposition solution, depositing for 100S under the condition that the potential is-0.5V, placing the working electrode in hot water, and stripping rhodium from the ITO conductive glass to prepare Rh.

the same procedure as in example 1 was followed except that the PPy/Rh prepared in example 1 was used_350sRh was substituted for the working electrode.

Results of studies on electrochemical characterization of electrodes during different modifications:

as shown in FIG. 1, polypyrrole and rhodium are simultaneously deposited on pretreated ITO conductive glass by a multi-potential alternating deposition method (multi-potential steps), in the process of electrodeposition, a positive potential value is firstly given to a working electrode, Py molecules begin to accumulate and polymerize on the surface of the electrode to form a PPy film; next, Rh present in the solution is applied while continuing to apply a negative voltage to the working electrode³⁺Ions are reduced into Rh simple substances and are embedded into the PPy membrane; and repeatedly continuing to supply negative potential and positive potential to the electrode, repeating the two deposition processes until the thickness of the electrode can be stripped, and soaking the electrode in hot water for 3-5min to obtain the polypyrrole/rhodium nanoparticle composite flexible electrode (PPy/Rh film). The PPy/Rh membrane is shown in FIG. 3;

as shown in FIG. 4, Gel Permeation Chromatography (GPC) showed that the weight average molecular weight of the resulting PPy at 0.8V deposition potential was about 10082 and the degree of polymerization was about 144, indicating successful polymerization of PPy.

In order to obtain the morphology structure of the polypyrrole/rhodium nanoparticle composite flexible electrode, SEM electron microscope scanning is carried out on the electrode, meanwhile, SEM electron microscope scanning is carried out on deposited Rh particles and polypyrrole, and comparison research is carried out; as shown in fig. 5a, the Rh particles deposited are in the form of clusters formed by clustering together small particles having a size of about 80 to 100 nm; PPy in FIG. 5b is a planar structure packed together by uniform hemispheres of about 100nm in diameter; the topography shown in FIG. 5c was obtained when Rh and PPy were deposited for 350s by multi-potential steps. It can be seen that the gray-white particles in the figure are Rh particles, which are uniformly dispersed on the surface of the PPy film, and compared with fig. 5a, it can be seen that the aggregation state of Rh is significantly improved, and the uniformly distributed state is favorable for charge transport between Rh and PPy and exposure of active sites.

The present invention also performs SEM characterization of the composite material deposited at different times, as shown in fig. 6, and it can be seen that the film structure is not substantially seen when the deposition time is only 55s, dense Rh particles are uniformly deposited on the surface of PPy after 150s, 240s, 500s as the deposition time increases, and the size of the particles gradually decreases as the deposition time increases. Since the size of the nanomaterial is closely related to the specific surface area thereof, when the size is reduced, the specific surface area is correspondingly increased. Therefore, the size of the particles is reduced, so that the specific surface area of the particles is increased, more active sites are exposed, and the catalytic performance is further improved.

Understanding the interaction between Rh and PPy, the present invention also performed XRD tests, as shown in FIG. 7, in conjunction with the XRD peak positions of PPy in FIG. 8, to determine Rh/PPy_350sXRD of (a) showed successful binding of PPy to Rh. At the same time, Rh/PPy_350sThe peak of the 111 crystal face of Rh is obviously widened relative to Rh, which indicates that the crystal structure is damaged to some extent, and is related to the combination of PPy, and meanwhile, the combination of PPy also causes the peak of other crystal faces of Rh to be weakened or even disappear to some extent, which is related to the strong amorphous state of PPy.

The invention further adopts the Raman scattering spectrum characterization to research the carbon peak appearance condition of the PPy. As can be seen from FIGS. 9 and 10, PPy is 1579cm^-1The peak at (A) represents the oscillation peak of C ═ C, and is at 1368cm^-1The peak appearance is the appearance of the C-N single bond.

When deposition times of Rh and PPy are 55s, 150s, 240s, 350s and 500s, respectively, raman shifts of C ═ C and C — N bonds are listed in table 3, and it can be seen that C ═ C peak appears red-shifted to different degrees, C — N peak appears blue-shifted to different degrees, and Rh/PPy_350sThe most extensive, indicating that electrons within PPy are transferred from a C ═ C double bond to a C — N bond after Rh is incorporated into PPy. And Rh/PPy_350sIs most pronounced, so that the electron shift in Rh/PPy is most pronounced_350sThe most electron imbalance centers will be generated inside the material.

Table 3 raman shift tables for C ═ C and C — N for different catalysts

Material	C＝C(cm^-1)	C-N(cm^-1)
			Rh/PPy_55s	1588	1335
Rh/PPy_150s	1590	1333
			Rh/PPy_240s	1594	1328
Rh/PPy_350s	1596	1318
			Rh/PPy_500s	1580	1361

XPS characterization also further demonstrated this result, as shown in FIG. 11a, the XPS narrow spectrum of Rh 3d is co-split into 4 peaks, of which Rh 3d, located at 307.4eV and 312.0eV, is_5/2And 3d_3/2The peak at 308.7 and 313.6eV is Rh ³⁺3d of_5/2And 3d_3/2Is likely due to oxidation of small amounts of Rh caused by exposure of the material to air. While Rh 3d at different deposition times is shown in FIG. 11b, it is clear that Rh/PPy is present_350sThe synthesis of (2) resulted in varying degrees of positive shift of Rh and showed the greatest positive shift value at a deposition time of 350s, indicating that Rh was electron-lost and Rh/PPy_350sThe material with the most electron loss of Rh. In both fig. 11c and 11d narrow spectra of N1s, at 398.2eV, 399.7eV and 400.8eV respectively representing-N ═ NH-and-NH-⁺Three N bonding modes. Meanwhile, when Rh is deposited for different times from PPy, it can be seen that doping of Rh causes a significant blue shift of the peak of N with respect to PPy, indicating that N is the electron-withdrawing species. In the Rh/PPy complex, Rh 3d and N1s were analyzed in combination with raman, and it was found that Rh serves as one of the electron donors, and transfers electrons to the N site in PPy, and that the C ═ C double bond in PPy also transfers electrons to the N site, so that Rh/PPy contains abundant electron disproportionated sites, and Rh/PPy generates abundant active sites, and further becomes a good catalytic material.

Based on the above analysis, electrochemical tests were performed on the obtained Rh/PPy, respectively; first, as shown in FIG. 12a, at 0.5mol H₂SO₄In the electrolyte of (1), Rh/PPy_350sWhen the concentration reaches 10mA cm^-2Only 59.5mV overpotential is needed, which is significantly lower than Rh/ITO (122.5mV) and compared to Pt/C (81.5mV) which has been commercialized at the same loading.

ICP data shows Rh content in composite films obtained at different deposition times, as shown in table 4:

TABLE 4 ICP testing of Rh in Rh/PPy films at different deposition times

	Rh/PPy_55s	Rh/PPy_150s	Rh/PPy_240s	Rh/PPy_350s	Rh/PPy_500s
						Rh loading (mgcm)^-2)	/	0.00192	0.01024	0.01576	0.02424

The invention also tested HER catalytic performance of Rh/PPy composites obtained at different deposition times,as shown in FIG. 13a, the corresponding overpotentials were 225.5mV (55s), 188.5mV (150s), 129.5mV (240s) and 101.5mV (500s), respectively, with Rh/PPy_55s，Rh/PPy_150sAnd Rh/PPy_240sThe membrane of (2) is not thick enough to obtain a separate membrane electrode, and Rh/PPy_500sPerformance of (d) with Rh/PPy_350sIn contrast, there is no significant advantage in performance, and the Rh loading is also greater than Rh/PPy_350sMuch larger (as shown in Table 4), resulting in waste of raw materials, therefore Rh/PPy_350sIs the optimal catalyst.

To further study the reaction kinetics of the above catalysts, Tafel slope plots were obtained from the polarization curves shown in FIGS. 12 and 13 (FIGS. 12b and 13b), with the Tafel slope for the 350s deposited catalyst being only 50.78mV dec^-1And the Tafel slopes of Rh/PPy for other deposition times were 117.16mV dec, respectively^-1(55s)，90.14mV dec^-1(150s)，86.14mV dec^-1(240s)，62.21mV dec^-1(500s) and the Tafel slope of Rh was 103.05mV dec^-1The Pt/C Tafel slope is 52.11mV dec^-1. Tafel slope is a parameter characterizing catalyst reaction kinetics, and a low tafel slope indicates that the catalyst has faster reaction kinetics during electrocatalysis, consistent with its trend of exhibiting HER catalytic performance.

An Electrochemical Impedance Spectroscopy (EIS) is shown in fig. 14, and by fitting the Electrochemical Impedance Spectroscopy (EIS), impedance values of different materials can be obtained, and the interfacial electron transfer capacity of the catalyst can be further evaluated. As can be seen, the resistance value at 350s of Rh/PPy deposition time was 7.15. omega. and was better than 27.51. omega. (Rh) and 12.43. omega. (Pt/C). While the other deposition times had impedance values of 78.32 Ω (55s), 33.43 Ω (150s), 22.61 Ω (240s), and 17.93 Ω (500s), respectively, it was found from the comparison of the impedance values with Rh that the composite exhibited the lowest impedance value when the deposition time was 350s, further indicating that the deposition time was the optimal deposition time, which resulted in the material having the fastest interfacial electron transfer capability, which was consistent with the results obtained from the polarization curve and the tafel slope. This indicates that the conductive structure of PPy can provide a fulcrum for Rh, further enhancing the conductivity of the catalyst.

The hydrophilicity of the material (0.5mol of H)₂SO₄) Also investigated by contact angle testing and the results are shown in FIG. 15, Rh/PPy_350sExhibits the best acidophilic capacity, which facilitates its full contact with the electrolyte during electrocatalysis, thereby facilitating the occurrence of water splitting.

Similarly, whether a catalyst can maintain substantially unchanged performance over a long period of electrocatalysis is also an important indicator for evaluating its performance, and therefore the present application performed stability tests, as shown in FIG. 16a, at 10mA cm^-2And 20mA cm^-2The catalyst can still maintain at least 24h of performance. At the same time, fig. 16b shows that there is still only a slight shift after a cycle of 5000 cycles. This indicates that the catalyst has good stability.

As the material shows good HER catalytic performance, PPy/Rh are treated to further explore the water cracking performance of the material_350s//RuO₂The two-electrode water splitting system is that Rh/PPy is used as a negative electrode, RuO₂As the positive electrode, 0.5mol of H was used₂SO₄As an electrolyte to an electrochemical workstation; Pt/C// RuO₂The two-electrode water cracking system is that Pt/C is used as a negative electrode, RuO₂As the positive electrode, 0.5mol of H was used₂SO₄Connecting the electrolyte to an electrochemical workstation, and testing the polarization curve of the electrolyte at 1-2V; both RuO at equal loading₂As a water splitting anode, Rh/PPy as a cathode, a water splitting test (FIG. 17a) was carried out, and when the potential value reached 1.66V, 10mA cm was reached^-2The current density of (1). At the same time, the material can maintain stability for at least 24h at 1.66V (fig. 17b), and in the process, the generation of bubbles can be clearly observed. This indicates that the material has good water splitting ability.

The Rh/PPy film deposited by taking ITO as a substrate can be easily stripped out after being soaked in hot water for 3-5 minutes, and the obtained independent film has good flexibility. As shown in fig. 18 a-d, the film can be bent, rolled or even folded into the shape of a kite, all indicating that the resulting composite film has good flexibility. Further electrochemical tests investigated the HER catalytic performance of the composite membrane before and after bending.

As shown in fig. 19, the polarization curves of HER catalytic process before and after bending of the composite film are shown, and the inset is a real image of the composite film as an independent electrode; it can be seen that there is no significant change in the polarization curve before and after bending, indicating that bending has no effect on the catalytic performance of the film. At the same time, its tafel slope also has negligible variation.

In conclusion, the invention successfully prepares the independent self-supporting polymer/nano particle composite film (Rh/PPy) by a one-step electrodeposition method; the substrate of the PPy membrane enables the Rh particles to be more dispersed, so that the specific surface area of Rh/PPy is increased, the further full exposure of active sites is promoted, meanwhile, the close combination between PPy and Rh enables electrons to be transferred, and electron imbalance centers are generated, so that the catalytic performance of HER is enhanced. Electrochemical testing demonstrated that Rh/PPy_350sCan reach 10mA cm at low overpotential of 59.5mV^-2The current density of (1) and the Tafel slope of the current density of (1) are only 50.78mV dec^-1The better stability is further demonstrated by the i-t and CV cycles. Moreover, thanks to the excellent mechanical properties of PPy, the independent electrode can also be bent into any shape, and the electrocatalytic properties thereof are substantially consistent before and after bending. The work of the invention provides a new idea for compounding the polymer and the inorganic nano material and also provides a new strategy for researching an independent self-supporting working electrode.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations. The above-mentioned embodiments are merely preferred embodiments for fully illustrating the present invention, and the scope of protection is not limited thereto. The equivalents and modifications of the present invention which may occur to those skilled in the art are within the scope of the present invention as defined by the appended claims.

Claims

1. The preparation method of the polypyrrole/rhodium nanoparticle composite flexible electrode is characterized by comprising the following steps:

(1) cleaning and cutting the ITO conductive glass;

(2) preparing a polypyrrole/rhodium nanoparticle composite flexible electrode:

wherein the mass ratio of the rhodium chloride monohydrate, the sulfuric acid and the pyrrole is 1:1: 2-5;

2. The method as claimed in claim 1, wherein the total deposition time of step S2 is 300-400S.

3. The method for preparing the polypyrrole/rhodium nanoparticle composite flexible electrode according to claim 1, wherein the specific steps of the multi-potential alternating deposition method of the step S2 are as follows: the working electrode is alternately placed under the potential condition of 0.8-1V for depositing for 20s and the potential condition of-0.6-0.4V for depositing for 10s, and the alternate deposition operation is carried out for codeposition for 350 s.

4. The polypyrrole/rhodium catalyst according to claim 1The preparation method of the nanoparticle composite flexible electrode is characterized in that the cleaning treatment method of the ITO conductive glass in the step (1) comprises the following steps: h with the mass fraction of 70 percent is adopted in sequence₂SO₄And washing the ITO glass for 10-20min by using the solution, deionized water and acetone, and drying.

5. The preparation method of the polypyrrole/rhodium nanoparticle composite flexible electrode according to claim 4, wherein the cleaned ITO conductive glass is cut to (1-3) × (2-3) cm in the step (1)²。

6. The polypyrrole/rhodium nanoparticle composite flexible electrode prepared by the preparation method of any one of claims 1 to 5.

7. The polypyrrole/rhodium nanoparticle composite flexible electrode of claim 6 is applied to the preparation of an electrolytic water catalytic electrode.

8. The application of the polypyrrole/rhodium nanoparticle composite flexible electrode in the preparation of an electrolytic water catalytic electrode according to claim 7 is characterized in that the electrolytic water catalytic reaction method comprises the following steps: and (2) taking an Ag/AgCl electrode containing saturated potassium chloride as a reference electrode, taking a platinum wire electrode as a counter electrode, forming a three-electrode system with the polypyrrole/rhodium nanoparticle composite flexible electrode as a working electrode, connecting the three-electrode system to electrochemical detection equipment, and electrolyzing by taking a sulfuric acid solution with the pH value of 0.2-1 as an electrolyte.