Method for quantifying formation rate of peroxide hydroxyl intermediate in electrocatalytic reaction

Abstract

The invention belongs to the technical field of electrochemical testing, and discloses a method for quantifying the formation rate of a peroxide hydroxyl intermediate in an electrocatalytic reaction. The invention finds that the catalyst still has charge exchange with solute ions in an open-circuit voltage state after an oxidation reaction, including the formation of * OOH and the formation of O2, and on this basis, the charge transfer amount in an OCV interval is subjected to integral quantification by controlling the retention time of the open-circuit voltage and then through a reduction pulse test. According to the method, the technical problem that the * OOH formation kinetics cannot be directly and quantitatively represented by a traditional method is solved, and an important tool is provided for the rational design of a high-efficiency electrochemical catalyst. Experimental results show that the method is suitable for various transition metal catalyst systems, and the measurement result is accurate and reliable.

Description

Technical Field

[0001] The invention relates to the technical field of electrochemical testing, and in particular to a method for quantifying the formation rate of a hydroxyl peroxide intermediate in an electrocatalytic reaction. Background Art

[0002] The reaction pathway of electrocatalytic reactions often includes multiple electron transfer processes, among which hydroxyl peroxide ( * The formation process of the OOH) intermediate is usually considered to be the rate-determining step, and its formation rate and reaction energy barrier directly determine the activity of the catalyst and the reaction overpotential.

[0003] However, the quantitative characterization of this key step still faces major technical challenges. Although traditional research methods such as Tafel slope analysis are widely used, they can only reflect the overall reaction kinetics and cannot distinguish * The contribution of this specific step of OOH formation is limited due to the inherent limitations of the multi-step electron transfer processes in many electrocatalytic reactions. Although spectroscopic characterization techniques such as in situ Raman and Fourier transform infrared spectroscopy can capture some information about reaction intermediates, they are unable to accurately predict the formation of OOH. * The detection sensitivity and time resolution of OOH intermediates are both insufficient, and there is a serious problem of signal overlap interference. Although theoretical calculation methods can provide predictions of reaction energy barriers, the calculation results based on idealized models often deviate significantly from the actual reaction conditions. More importantly, existing technologies cannot directly measure the reaction energy barrier at the experimental level. * The real-time kinetic parameters of OOH formation, this technical gap seriously restricts the rational design and performance optimization of electrocatalysts. Especially in the research of highly active transition metal catalyst systems, due to the lack of reliable * In the quantitative method of OOH formation rate, researchers can only infer the intrinsic characteristics of catalytic active sites through indirect parameters, which greatly limits the development process of new catalyst materials.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] To solve the problems in the background technology, the present invention provides a method for quantifying the formation rate of hydroxyl peroxide intermediates in electrocatalytic reactions.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: Methods for quantifying the rate of formation of peroxyhydroxyl intermediates in electrocatalytic reactions include: loading the catalyst on the working electrode and performing electrochemical pretreatment; Setting multiple different open circuit voltage holding times, wherein each open circuit voltage holding time does not exceed 240 seconds; For each set open circuit voltage hold time, perform the following test process: apply an oxidation potential of 1.45–1.80 V vs. RHE to the pretreated working electrode; apply the open circuit voltage and hold it for the currently set time; apply a reduction pulse potential of 1.20–1.40 V vs. RHE; record the reduction pulse current response of this cycle; after completing the current open circuit voltage hold time test, proceed to the next open circuit voltage hold time test; The current response corresponding to each open circuit voltage holding time was integrated separately, and the net charge transfer amount at different open circuit voltage times was calculated. Combined with the normalization of the electrochemical active area, the charge transfer amount-time curve was fitted, and its slope was taken to quantify the formation rate of peroxyhydroxyl intermediates.

[0007] Preferably, the catalyst precursor is any catalyst system capable of generating peroxyhydroxyl groups.

[0008] Preferably, the electrochemical pretreatment is anodization at a current density of 5–100 mA / cm² for 0.1–48 hours, followed by a reduction potential of 1.20–1.40 V vs. RHE for 1–60 minutes.

[0009] Preferably, before applying the open circuit voltage, the method further comprises polarizing the pretreated working electrode at a potential of 1.45-1.80 V vs. RHE for 5-600 seconds.

[0010] Preferably, the duration of the reduction pulse potential is 10-600 seconds.

[0011] Preferably, the net charge transfer amount Q m The calculation formula is: Q m =(Q1–Q2) / 2, where Q1 is the total charge and Q2 is the background charge.

[0012] Preferably, the electrochemically active area is measured by cyclic voltammetry with a scan rate range of 1-200 mV / s.

[0013] Preferably, the unit of the peroxyhydroxy intermediate formation rate is mmol·cm -2 ·s -1 , obtained by fitting the slope of the charge-time curve and converting the units.

[0014] Preferably, each open circuit voltage is maintained for no longer than 10 seconds.

[0015] Preferably, each open circuit voltage holding time does not exceed 1.8 seconds.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This study discovered that even at the open-circuit voltage after the oxidation reaction, the catalyst still undergoes charge exchange with solute ions, including the formation of *OOH and O₂. Based on this, the charge transfer in the OCV interval is quantified by controlling the hold time of the open-circuit voltage and then performing a reduction pulse test. This method overcomes the technical difficulty of traditional methods in directly and quantitatively characterizing the kinetics of *OOH formation, providing an important tool for the rational design of efficient electrochemical catalysts. Experimental results demonstrate that this method is applicable to a variety of transition metal catalyst systems and produces accurate and reliable measurements. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 To test the effect of OCV process on the electron transfer pathway of adsorption evolution mechanism in OER reaction; Figure 2 This is the in situ O K-edge XAS spectrum, showing the change of the O characteristic peak at 528.9 eV with increasing potential; Figure 3 The curve of the change of the O K-edge XAS characteristic peak intensity over time during the OCV process; Figure 4 In situ Ni K-edge XAS spectrum, showing the change of Ni absorption edge energy during constant potential polarization and OCV stages; Figure 5 This is a schematic diagram of the OCV-PV test process and principle of the present invention; Figure 6 The OCV application time is different * Changes in OOH formation Figure 7 This is a comparison chart of DEMS test results, proving that the amount of electrons used for oxygen-oxygen coupling in the OCV stage is negligible compared to the amount of primary electrons. Figure 8 At different potentials * Comparison results of OOH formation rate; Figure 9 Schematic diagram of the OCV-PV test procedure for Example 1; Figure 10 This is the low potential response current integral curve of Example 1 at 1.503V; Figure 11 ECSA determination and calculation curve of Example 1; Figure 12 For example 1 * OOH formation rate fitting curve; Figure 13-15 They are the current integration, ECSA determination and * OOH formation rate fitting curve. DETAILED DESCRIPTION

[0018] In order to more clearly illustrate the technical scheme, implementation process and beneficial effect of the present invention, the specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the following examples are only used to help understand the core content of the present invention and are not intended to limit the scope of protection. For those skilled in the art, without departing from the principles of the present invention, some technical details can also be adjusted or replaced according to actual needs. In the specific implementation process, unless otherwise specified, the experimental conditions involved are all conventional operations in this area or are performed according to the standards recommended by the instrument and equipment manufacturer. The chemical reagents and materials used are all commercially available general products if their specific sources are not indicated.

[0019] Feasibility study of the present invention: The present invention first systematically demonstrates the open circuit voltage-pulse voltammetry (OCV-PV) determination * The scientificity and feasibility of the rate of formation of OOH intermediates. Taking the oxygen evolution reaction (OER) as an example, at the theoretical mechanism level, the AEM four-step reaction mechanism of the OER reaction includes two processes of transferring electrons from the catalyst to the external circuit and two processes of transferring electrons from the electrolyte to the catalyst. Figure 1 As shown, ① is the oxygen release path of oxygen-oxygen coupling, ② is * The formation process of OOH intermediates. By introducing the special state of open circuit voltage (OCV), the catalyst can selectively block the electron transfer of the external circuit while fully retaining the OH in the electrolyte. - This unique electron transfer regulation mechanism enables selective maintenance of the OER process while blocking the overall OER process. * The OOH formation reaction and the oxygen-oxygen coupling reaction continue.

[0020] Subsequently, the present invention demonstrated the OCV process through in situ X-ray absorption spectroscopy (XAS) system. * The persistence of OOH formation and the characteristics of Ni valence change. The specific method is: first, the NiOOH catalyst is treated at a constant voltage of 1.36 V, 1.46 V, and 1.56 V for 5 minutes, and then the OK-edge XAS characterization results are immediately performed on it and compared with the OK-edge XAS characterization results of the initial NiOOH catalyst that has not been treated with constant voltage. The results are shown in the figure. Figure 2 As shown, from Figure 2 It can be seen that the * The intensity of the O characteristic peak increases with increasing potential (1.36 V to 1.56 V), indicating that the hydrogen ion coverage of the NiOOH surface decreases. Figure 3In the experiment shown, the applicant treated the NiOOH catalyst with a constant voltage of 1.5 V for 20 minutes, then applied OCV for different times, and immediately performed O K-edge XAS characterization after 0 minutes, 5 minutes, and 10 minutes of OCV testing. The results show that during the OCV process * The intensity of the characteristic peak of O gradually weakened with time (refer to Figure 3 , Figure 3 The black, red and blue lines in the middle are the O K-edge XAS spectra at OCV time of 0min, 5min and 10min, respectively. * O through with OH - The reaction is consumed. Figure 4 In the present invention, the inventors subjected the NiOOH catalyst to a constant voltage treatment of 1.5 V, and then immediately connected it to the OCV test, and performed Ni K-edge XAS characterization on the samples treated with constant voltage for 10 min and 20 min, and the samples treated with OCV for 4 min, 8 min and 12 min. The results showed that the Ni absorption edge gradually blue-shifted at 1.5 V polarization, which means that the valence state of Ni increased to 3+x (x>0) as the reaction proceeded, while the Ni absorption edge gradually red-shifted during the OCV period, which means that the valence state of Ni decreased with the increase of OH. - The electron supply gradually decreases. It is particularly noteworthy that it takes 12 minutes for the Ni valence state to recover to +3, while * The generation rate of OOH is related to the oxidation state of Ni. Based on finite element analysis, it is known that in a short period of time * The OOH formation rate can be considered constant.

[0021] After the theory is formally feasible, the OCV-PV test process proposed in this invention has the following test principles: Figure 5 As shown in the figure: Under each open circuit voltage holding time (OCV time), the working electrode is first polarized at a higher potential of 1.453 V vs. RHE for 60 seconds; then the working potential is switched to a lower potential of 1.373 V vs. RHE and held for 72 seconds; during the high and low potential switching process, an open circuit voltage (OCV) test stage is set. By subtracting the integral results of the reduction current curve before and after the cycle test and dividing by 2, the OCV process can be obtained. * The amount of OOH generated. Test results are as follows Figure 6 As shown, the OCV time is 0-240s, and the time gradient (i.e., the difference between the last open circuit voltage holding time and the previous open circuit voltage holding time) is 10s. The test results are consistent with the theoretical prediction. As the OCV time increases, * The formation rate of OOH is decreasing, so the OCV time can be selected from 0 to 240 seconds. When the OCV time exceeds 2 minutes, the newly added* The amount of OOH is very small, and the first 10s * The OOH formation rate is the fastest, which is conducive to quantitative comparison. The smaller the OCV time, the more obvious the test results. Therefore, the OCV time is preferably 0-120s, and more preferably 0-10s. Furthermore, under the premise that the test sensitivity of the electrochemical workstation meets the requirements, it is preferred to select the smallest possible OCV application time. According to the sensitivity of the electrochemical workstation used in the present invention, 0-1.8s is used as the OCV time in the following specific embodiments. In addition, the present invention uses in-situ differential electrochemical mass spectrometry (DEMS) to monitor the oxygen-oxygen coupling step in the reaction. Figure 5 The test process shown is connected to the in-situ differential electrochemical mass spectrometry (DEMS) for oxygen isotope testing, with an OCV time of 0-1.8s. Figure 7 The DEMS results show that during the OCV process, the total charge obtained from the measurement (i.e., the charge from the electrolyte to the Ni 4+ Compared with the sum of the transferred electrons and the electrons contributed by oxygen-oxygen coupling, the recorded charge from oxygen evolution (i.e., the electrons contributed by oxygen-oxygen coupling in the figure) can be ignored. Therefore, the calculated charge is infinitely close to the charge formed. * The amount of charge transferred by OOH. Figure 8 As shown, the resulting charge is the red line * The fitting curve of the OOH formation rate at low voltage (slope is 2.34E-7), the blue line is * The fitting curve of OOH formation rate at high voltage (slope is 1.35E-6) shows that the voltage increase at high voltage has a significant effect on the formation rate of OOH. * The promotion effect of voltage increase on OOH formation rate is greater than that at low voltage. * The promoting effect on the OOH formation rate is consistent with the facts.

[0022] Based on the above feasibility demonstration, the embodiment of the present invention provides a method for quantifying the formation rate of peroxyhydroxyl intermediates in electrocatalytic reactions, including: loading the catalyst on the working electrode and performing electrochemical pretreatment; Setting multiple different open circuit voltage holding times, wherein each open circuit voltage holding time does not exceed 240 seconds; For each set open circuit voltage hold time, perform the following test process: apply an oxidation potential of 1.45–1.80 V vs. RHE to the pretreated working electrode; apply the open circuit voltage and hold it for the currently set time; apply a reduction pulse potential of 1.20–1.40 V vs. RHE; record the reduction pulse current response of this cycle; after completing the current open circuit voltage hold time test, proceed to the next open circuit voltage hold time test; The current response corresponding to each open circuit voltage holding time was integrated separately, and the net charge transfer amount at different open circuit voltage times was calculated. Combined with the normalization of the electrochemical active area, the charge transfer amount-time curve was fitted, and its slope was taken to quantify the formation rate of peroxyhydroxyl intermediates.

[0023] The current state of the art is unable to determine the duration of open-circuit voltage, nor is the specific electron transfer process occurring under open-circuit voltage conditions known. This invention, for the first time, discovered that charge exchange between the catalyst and solute ions, including the formation of *OOH and O2, continues even under open-circuit voltage. Therefore, the open-circuit voltage is used to disconnect the electron exchange between the catalyst and the external circuit, maintaining the open-circuit voltage between 0 and 240 seconds. Simultaneously, in-situ differential electrochemical mass spectrometry (DEMS) is used to exclude electrons involved in oxygen-oxygen coupling, and pulse voltammetry is combined to quantify the *OOH formation rate.

[0024] During the above open circuit voltage-pulse voltammetry test, at each open circuit voltage holding time (i.e., at each cycle), the purpose of first applying an oxidation potential to the pre-treated NiOOH is to convert the +3 valence Ni to +4 valence Ni through a high potential; then applying an open circuit voltage, during which a portion of the +4 valence Ni spontaneously changes to +3 valence, accompanied by the generation of *OOH; finally, applying a reduction pulse potential to convert the +4 valence Ni back to +3 valence, calculating the integral of the current curve of all the cycle processes, and obtaining the amount of electrostatic charge transfer. The time for applying the oxidation potential can be determined by those skilled in the art as needed. The longer the oxidation potential is applied, the more Ni 4+ The more, the longer the reduction potential application time is. In some preferred embodiments, in order to make Ni 4+ In order to reduce the metal as completely as possible, the reduction potential application time is about 20% longer than the oxidation potential time.

[0025] The present invention does not limit the time gradient between the latter open-circuit voltage holding time and the previous open-circuit voltage holding time, and those skilled in the art can reasonably set it according to the selected open-circuit voltage holding time.

[0026] The catalyst precursors that can be used in the present invention are all catalyst systems that can generate peroxyhydroxyl groups.

[0027] The electrochemical pretreatment of the working electrode is a catalyst pretreatment method commonly used in the art. The catalyst precursor is supported on a conductive substrate and first subjected to electrochemical oxidation in an electrolyte to convert all hydroxides into oxyhydroxides. A reduction potential is then applied to completely transfer all oxidative charges accumulated within the catalyst during the aforementioned oxidation process to the external circuit. There is no specific limitation on the specific parameters of the reduction potential, and it is preferably the case that the current response at this reduction potential reaches stability. In a preferred embodiment, the electrochemical oxidation treatment is an anodic oxidation treatment at a current density of 5-100 mA / cm² for 0.1-48 hours, and the reduction potential is 1.20-1.40V vs. RHE for 1-60 minutes.

[0028] Before applying the open-circuit voltage, a high voltage must be applied to allow the catalyst current to reach a steady state. Different electrocatalytic reactions or catalyst types require different times to reach steady state. Those skilled in the art will adapt the specific voltage and time applied based on the catalyst type or electrocatalytic reaction. For example, for Ni-based OER catalysts, the pretreated working electrode can be polarized at a potential of 1.45–1.80 V vs. RHE for 5–600 seconds.

[0029] For the reduction pulse potential of the present application, there is no particular limitation on the duration and voltage, as long as the current response curve remains stable. For example, the duration can be 10-600 seconds.

[0030] In the above method, the net charge transfer amount Q m The calculation formula is: Q m =(Q1–Q2) / 2, where Q1 is the total charge and Q2 is the background charge.

[0031] In some preferred embodiments, the electrochemically active area is measured by cyclic voltammetry with a scan rate range of 1-200 mV / s.

[0032] The unit of the peroxyhydroxyl intermediate formation rate in the embodiment of the present invention is mmol·cm -2 ·s -1 , obtained by fitting the slope of the charge-time curve and converting the units.

[0033] To make the present invention clearer, the quantification method and effect of the formation rate of the peroxyhydroxyl intermediate in the electrocatalytic reaction are described in detail below through multiple specific examples.

[0034] Example 1: Pure NiOOH catalyst * Determination of OOH formation rate First, the catalyst pretreatment step was carried out: the Ni(OH)2 precursor material was heated at 10 mA cm -2 Electrochemical oxidation treatment was performed under a constant current density of 1.373 V for 1 hour to ensure complete conversion to catalytically active NiOOH species. The working electrode potential was then precisely and stably maintained at a reduction potential of 1.373 V vs. RHE for 10 minutes. This step ensured that all oxidative charges accumulated within the NiOOH catalyst during the previous oxidation process were completely transferred to the external circuit, restoring the catalyst to a uniform initial state.

[0035] The test process used a standard three-electrode electrochemical test system, in which the working electrode was a NiOOH / carbon cloth electrode, and the catalyst loading on the carbon cloth substrate was strictly controlled to 1 mg cm -2 A high-purity platinum electrode was used as the counter electrode, and a rigorously calibrated Hg / HgO electrode was used as the reference electrode. All electrochemical tests were performed at a constant temperature of 25°C using purified 1.0 M KOH solution as the electrolyte.

[0036] The specific procedure of the OCV-PV test is as follows: In each cycle, the working electrode is first polarized at a higher potential of 1.453 V vs. RHE, and the polarization time is strictly controlled to 10 seconds. The working potential is then switched to a lower potential of 1.373 V vs. RHE and maintained for 12 seconds. During the high-low potential switching process, the open circuit voltage (OCV) test phase is set from the second cycle onwards. The OCV test time starts from 0.8 seconds and is gradually increased in increments of 0.2 seconds to 1.8 seconds (for the specific test procedure, see Figure 9 , Figure 9 The blue line on the upper side is the current response line of constant potential oxidation, the blue line on the lower side is the current response curve of constant potential reduction, the time above the blue line is the OCV time applied between the corresponding oxidation potential and reduction potential, and the horizontal axis time is the total test time); in order to fully examine the influence of potential, the test potential (E h ) started from 1.453 V and increased gradually to 1.523 V in steps of 10 mV while maintaining the reduction potential (E l ) is constant at 1.373 V vs. RHE.

[0037] The data processing method is as follows: First, the current response curve of the cathode voltage pulse stage is accurately integrated (see the integral curve for details). Figure 10 , taking the result at 1.503 V as an example), calculate the total charge Q1; then use Q m = (Q1-Q2) / 2 calculation formula, accurately derive the OCV time period * The net charge transfer amount Q for OOH formationm The electrochemically active area (ECSA) was determined by cyclic voltammetry in the test potential range of 0.02–0.12 V vs. Hg / HgO at 10, 20, 30, 40, and 50 mV s -1 Five different scan rates were tested, and 0.04 mF cm was used. -2 The standard specific capacitance value is calculated to obtain ECSA = 27.5 cm 2 (For specific calculation curves, see Figure 11 ).

[0038] After normalizing the charge Q at different times to the ECSA and fitting it, the slope of the fitting curve is used to evaluate * OOH formation rate (taking the data at 1.503 V as an example, see Figure 12 , take the slope of the fitting curve as 0.004 mC·cm 2 ·, after unit conversion: 0.004 / 96320, we can get, at 1.503 V * The formation rate of OOH is 4.15×10 -8 mmol·cm -2 ·s -1 ). In the test potential range of 1.453 V to 1.523 V, * The OOH formation rate showed a significant potential dependence, with the specific value ranging from 2.18×10 -8 mmol cm -2 s -1 Steadily increased to 6.96×10 -8 mmol cm -2 s -1 .

[0039] Example 2: Co-NiOOH catalyst * Determination of OOH formation rate First, the catalyst pretreatment step was carried out: the Co-doped Ni(OH)2 precursor material (Co doping amount was 2 at%) was heated at 10 mA cm -2 The electrochemical oxidation treatment was carried out under a constant current density of 1.5 hours to ensure its complete conversion to the catalytically active Co-NiOOH species. The working electrode potential was then precisely and stably maintained at the reduction potential of 1.373 V vs. RHE for 15 minutes. This step ensured that all oxidative charges accumulated within the Co-NiOOH catalyst during the previous oxidation process were completely transferred to the external circuit, restoring the catalyst to a uniform initial state.

[0040] The test process used a standard three-electrode electrochemical test system, in which the working electrode was a Co-NiOOH / carbon cloth electrode, and the catalyst loading on the carbon cloth substrate was strictly controlled to 2 mg cm -2 A high-purity platinum electrode was used as the counter electrode, and a rigorously calibrated Hg / HgO electrode was used as the reference electrode. All electrochemical tests were performed at a constant temperature of 25°C using purified 1.0 M KOH solution as the electrolyte.

[0041] The specific procedure of the OCV-PV test is as follows: In each cycle, the working electrode is first polarized at a constant potential of 1.503 V vs. RHE, and the polarization time is strictly controlled within 10 seconds; then the working potential is switched to a lower potential of 1.373 V vs. RHE and maintained for 12 seconds; during the high-low potential switching process, an open circuit voltage (OCV) test phase is set from the second cycle onwards, and the OCV test time starts from the initial 0.8 seconds and gradually increases to 1.8 seconds in increments of 0.2 seconds. Test potential (E h ) is constant at 1.503 V vs. RHE while maintaining the reduction potential (E l ) is constant at 1.373 V vs. RHE.

[0042] The data processing method is as follows: First, the current response curve of the cathode voltage pulse stage is accurately integrated (see the integral curve for details). Figure 13 ), calculate the total charge Q1; then use Q m = (Q1-Q2) / 2 calculation formula, accurately derive the OCV time period * The net charge transfer amount of OOH was formed. The electrochemically active area (ECSA) was determined by cyclic voltammetry in the test potential range of 0.02-0.12 V vs. Hg / HgO at 10, 20, 30, 40, and 50 mVs -1 Five different scan rates were tested, and 0.04 mF cm was used. -2 The standard specific capacitance value is calculated to be ECSA = 26.275 cm 2 (For specific test curves, see Figure 14 ).

[0043] After normalizing the charge Q at different times to the ECSA and fitting, the slope of the fitting curve was taken as 0.0053 mC cm -2 For evaluation * OOH formation rate (for detailed data see Figure 15 After unit conversion, it can be concluded that at a constant test potential of 1.503 V, the Co-NiOOH catalyst *The OOH formation rate is 5.50×10 -8 mmol cm -2 s -1 .

[0044] Example 3: Cr-NiOOH catalyst * Determination of OOH formation rate First, the catalyst pretreatment step was carried out: the Cr-doped Ni(OH)2 precursor material (Cr doping amount was 2 at%) was heated at 10 mA cm -2 Electrochemical oxidation treatment was performed under a constant current density of 1.5 hours to ensure its complete conversion to catalytically active Cr-NiOOH species. The working electrode potential was then precisely and stably maintained at a reduction potential of 1.373 V vs. RHE for 15 minutes. This step ensured that all oxidative charges accumulated within the Cr-NiOOH catalyst during the previous oxidation process were completely transferred to the external circuit, restoring the catalyst to a uniform initial state.

[0045] The test process used a standard three-electrode electrochemical test system, in which the working electrode was a Cr-NiOOH / carbon cloth electrode, and the catalyst loading on the carbon cloth substrate was strictly controlled to 2 mg cm -2 A high-purity platinum electrode was used as the counter electrode, and a rigorously calibrated Hg / HgO electrode was used as the reference electrode. All electrochemical tests were performed at a constant temperature of 25°C using purified 1.0 M KOH solution as the electrolyte.

[0046] The specific procedure of the OCV-PV test is as follows: In each cycle, the working electrode is first polarized at a constant potential of 1.503 V vs. RHE, and the polarization time is strictly controlled within 10 seconds; then the working potential is switched to a lower potential of 1.373 V vs. RHE and maintained for 12 seconds. During the high-low potential switching process, an open circuit voltage (OCV) test phase is set from the second cycle onwards. The OCV test time starts from the initial 0.8 seconds and gradually increases to 1.8 seconds in increments of 0.2 seconds. Test potential (E h ) is constant at 1.503 V vs. RHE while maintaining the reduction potential (E l ) is constant at 1.373 V vs. RHE.

[0047] The data processing method is as follows: first, the current response curve of the cathode voltage pulse stage is accurately integrated to calculate the total charge Q1; then Q m = (Q1-Q2) / 2 calculation formula, accurately derive the OCV time period *The net charge transfer amount of OOH formation was determined by cyclic voltammetry (ECSA) with a test potential range of 0.02–0.12 V vs. Hg / HgO at 10, 20, 30, 40, and 50 mV s -1 Five different scan rates were tested, and 0.04 mF cm was used. -2 The standard specific capacitance value is calculated to obtain ECSA = 21.1 cm 2 .

[0048] The charge Q at different times was normalized to ECSA and a linear fit was performed, and the slope of the fitting curve was taken as 0.0045 mC cm -2 s -1 For evaluation * OOH formation rate. After unit conversion, it is found that at a constant test potential of 1.503 V, the OOH formation rate of Cr-NiOOH catalyst is * The OOH formation rate is 4.67×10 -8 mmol cm -2 s -1 .

[0049] Example 4: Mn-NiOOH catalyst * Determination of OOH formation rate First, the catalyst pretreatment step was carried out: the Mn-doped Ni(OH)2 precursor material (Mn doping amount was 2 at%) was placed in an electrolytic cell and heated at 10 mA cm -2 Electrochemical oxidation was performed for 1.5 hours at a constant current density to ensure complete conversion of the precursor into catalytically active Mn-NiOOH. During the oxidation process, complete conversion was confirmed by real-time monitoring of the electrode potential. The working electrode potential was then precisely and stably maintained at a reduction potential of 1.373 V vs. RHE for 15 minutes. This step ensured that all oxidative charges accumulated within the Mn-NiOOH catalyst during the previous oxidation process were completely transferred to the external circuit, restoring the catalyst to a uniform initial state.

[0050] The test process used a standard three-electrode electrochemical test system, in which the working electrode was a Mn-NiOOH / carbon cloth electrode, and the catalyst loading on the carbon cloth substrate was strictly controlled to 2 mg cm by precise weighing. -2 A high-purity platinum electrode was used as the counter electrode, and a rigorously calibrated Hg / HgO electrode was used as the reference electrode. All electrochemical tests were performed at a constant temperature of 25°C using purified 1.0 M KOH solution as the electrolyte.

[0051] The specific procedure of the OCV-PV test is as follows: In each cycle, the working electrode is first polarized at a constant potential of 1.503 V vs. RHE, and the polarization time is strictly controlled within 10 seconds; then the working potential is switched to a lower potential of 1.373 V vs. RHE and maintained for 12 seconds. During the high-low potential switching process, an open circuit voltage (OCV) test phase is set from the second cycle onwards. The OCV test time starts from the initial 0.8 seconds and gradually increases to 1.8 seconds in increments of 0.2 seconds. Test potential (E h ) is constant at 1.503 V vs. RHE while maintaining the reduction potential (E l ) is constant at 1.373 V vs. RHE.

[0052] The data processing method is as follows: first, the current response curve of the cathode voltage pulse stage is accurately integrated to calculate the total charge Q1; then Q m = (Q1-Q2) / 2 calculation formula, accurately derive the OCV time period * The net charge transfer amount of OOH formation was determined by cyclic voltammetry (ECSA) with a test potential range of 0.02–0.12 V vs. Hg / HgO at 10, 20, 30, 40, and 50 mV s -1 Five different scan rates were tested, and 0.04 mF cm was used. -2 The standard specific capacitance value is calculated to obtain ECSA = 28.8 cm 2 .

[0053] The charge Q at different times was normalized to ECSA and a linear fit was performed, and the slope of the fitting curve was taken as 0.0099 mC cm -2 s -1 For evaluation * OOH formation rate. After unit conversion, it is found that at a constant test potential of 1.503 V, the OOH formation rate of the Mn-NiOOH catalyst is * The OOH formation rate is 1.02×10 -7 mmol cm -2 s -1 .

[0054] Example 5: Fe-NiOOH catalyst * Determination of OOH formation rate First, the catalyst pretreatment step was carried out: Fe-doped Ni(OH)2 precursor material (Fe doping amount was 2 at%) was placed in an electrolytic cell and heated at 10 mA cm -2Electrochemical oxidation was performed for 1.5 hours at a constant current density to ensure complete conversion of the precursor into catalytically active Fe-NiOOH. During the oxidation process, complete conversion was confirmed by real-time monitoring of the electrode potential. The working electrode potential was then precisely and stably maintained at a reduction potential of 1.373 V vs. RHE for 15 minutes. This step ensured that all oxidative charges accumulated within the Fe-NiOOH catalyst during the previous oxidation process were completely transferred to the external circuit, restoring the catalyst to its uniform initial state.

[0055] The test process uses a standard three-electrode electrochemical test system, in which the working electrode is a Fe-NiOOH / carbon cloth electrode, and the catalyst loading on the carbon cloth substrate is strictly controlled by precise weighing to 2 mg cm -2 A high-purity platinum electrode was used as the counter electrode, and a rigorously calibrated Hg / HgO electrode was used as the reference electrode. All electrochemical tests were performed at a constant temperature of 25°C using purified 1.0 M KOH solution as the electrolyte.

[0056] The specific procedure of the OCV-PV test is as follows: In each cycle, the working electrode is first polarized at a constant potential of 1.503 V vs. RHE, and the polarization time is strictly controlled within 10 seconds; then the working potential is switched to a lower potential of 1.373 V vs. RHE and maintained for 12 seconds. During the high-low potential switching process, an open circuit voltage (OCV) test phase is set from the second cycle onwards. The OCV test time starts from the initial 0.8 seconds and gradually increases to 1.8 seconds in increments of 0.2 seconds. Test potential (E h ) is constant at 1.503 V vs. RHE while maintaining the reduction potential (E l ) is constant at 1.373 V vs. RHE.

[0057] The data processing method is as follows: first, the current response curve of the cathode voltage pulse stage is accurately integrated to calculate the total charge Q1; then Q m = (Q1-Q2) / 2 calculation formula, accurately derive the OCV time period * The net charge transfer amount of OOH formation was determined by cyclic voltammetry (ECSA) with a test potential range of 0.02–0.12 V vs. Hg / HgO at 10, 20, 30, 40, and 50 mV s -1 Five different scan rates were tested, and 0.04 mF cm was used. -2 The standard specific capacitance value is calculated to be ECSA = 28.8 cm².

[0058] The charge Q at different times was normalized to ECSA and a linear fit was performed, and the slope of the fitting curve was taken as 0.0099 mC cm -2 s -1 For evaluation * OOH formation rate. After unit conversion, it is found that at a constant test potential of 1.503 V, the Fe-NiOOH catalyst * The OOH formation rate is 1.02×10 -7 mmol cm -2 s -1 .

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. As long as the catalyst follows the AEM mechanism in the OER reaction, appropriate test parameters can be selected and tested by the test method mentioned in the present invention. * Therefore, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for quantifying the rate of formation of a peroxyhydroxyl intermediate in an electrocatalytic reaction, characterized in that: include: loading the catalyst on the working electrode and performing electrochemical pretreatment; Setting multiple different open circuit voltage holding times, wherein each open circuit voltage holding time does not exceed 240 seconds; The following test process was performed for each set open circuit voltage hold time: an oxidation potential of 1.45–1.80 V vs. RHE was applied to the pretreated working electrode; the open circuit voltage was applied and held for the currently set time; a reduction pulse potential of 1.20–1.40 V vs. RHE was applied; the reduction pulse current response of this cycle was recorded. After completing the current open circuit voltage hold time test, the next open circuit voltage hold time test was performed. The current response corresponding to each open circuit voltage holding time was integrated separately, and the net charge transfer amount at different open circuit voltage times was calculated. Combined with the normalization of the electrochemical active area, the charge transfer amount-time curve was fitted, and its slope was taken to quantify the formation rate of peroxyhydroxyl intermediates.

2. The method for quantifying the formation rate of a peroxyhydroxyl intermediate in an electrocatalytic reaction according to claim 1, wherein: The precursor of the catalyst is any catalyst system capable of generating peroxyhydroxyl groups.

3. The method for quantifying the formation rate of peroxyhydroxyl intermediates in an electrocatalytic reaction according to claim 1, wherein: The electrochemical pretreatment consisted of anodization at a current density of 5–100 mA / cm² for 0.1–48 h, followed by a reduction potential of 1.20–1.40 V vs. RHE for 1–60 min.

4. The method for quantifying the formation rate of a peroxyhydroxyl intermediate in an electrocatalytic reaction according to claim 1, wherein: The pretreated working electrode was polarized at 1.45–1.80 V vs. RHE for 5–600 s before applying the open circuit voltage.

5. The method for quantifying the formation rate of a peroxyhydroxyl intermediate in an electrocatalytic reaction according to claim 1, wherein: The duration of the reduction pulse potential was 10–600 s.

6. The method for quantifying the formation rate of a peroxyhydroxyl intermediate in an electrocatalytic reaction according to claim 1, wherein: Net charge transfer Q m The calculation formula is: Q m =(Q1–Q2) / 2, where Q1 is the total charge and Q2 is the background charge.

7. The method for quantifying the formation rate of peroxyhydroxyl intermediates in an electrocatalytic reaction according to claim 1, wherein: The electrochemical active area was measured by cyclic voltammetry with a scan rate range of 1–200 mV / s.

8. The method for quantifying the formation rate of peroxyhydroxyl intermediates in an electrocatalytic reaction according to claim 1, wherein: The unit of the rate of formation of peroxyhydroxy intermediate is mmol·cm -2 ·s -1 , obtained by fitting the slope of the charge-time curve and converting the units.

9. The method for quantifying the formation rate of peroxyhydroxyl intermediates in an electrocatalytic reaction according to claim 1, wherein: Each open circuit voltage is maintained for no more than 10 seconds.

10. The method for quantifying the formation rate of peroxyhydroxyl intermediates in an electrocatalytic reaction according to claim 1, wherein: Each open circuit voltage is maintained for no more than 1.8 seconds.

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