CN115522224A - Novel catalyst material, preparation method and application thereof - Google Patents
Novel catalyst material, preparation method and application thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
- C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
- C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
- C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
- C25B11/091—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B1/00—Electrolytic production of inorganic compounds or non-metals
- C25B1/01—Products
- C25B1/02—Hydrogen or oxygen
- C25B1/04—Hydrogen or oxygen by electrolysis of water
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
Abstract
The invention belongs to the technical field of electrochemistry, and particularly relates to a novel catalyst material, a preparation method and application thereof. The novel catalyst material is La 2 IrO 6 And IrO 2 The hollow nano-tube structure with the heterojunction characteristic is formed by compounding, and has stably existing high-valence iridium atoms. The novel catalyst material provided by the invention has excellent acidic OER catalytic activity in acidic oxygen precipitation, shows excellent catalytic stability and is an oxygen evolution reaction catalyst with great potential.
Description
Technical Field
The invention belongs to the technical field of electrochemistry, and particularly relates to a novel catalyst material, a preparation method and application thereof.
Background
The electrolysis of water to produce hydrogen is considered to be a promising energy conversion technology. Compared with the hydrogen evolution reaction of two electrons, the anodic Oxygen Evolution Reaction (OER) is a process with multi-proton/electron coupling and slow kinetics, and restricts the development of the industrialization of the electrolyzed water. Therefore, the development of efficient and stable OER catalysts is urgently needed. The electrolytic water can be carried out under both acidic and alkaline conditions, catalytic materials for anodic oxygen evolution reaction in alkaline media are studied very much, but the ionic conductivity of alkaline electrolytes is obviously lower than that of hydronium ions, and carbonate pollutants are easily accumulated by the reaction with carbon dioxide. Compared with alkaline electrolyzers, proton Exchange Membrane (PEM) electrolyzers have significant advantages, including higher ionic conductivity, fewer side reactions, higher current density and higher purity hydrogen. Therefore, the research on the anode reaction under the acidic condition has important practical significance for promoting the electrochemical decomposition of water.
Currently, most catalysts applied to basic OER have proven to be incapable of stable operation in PEM for long periods of time. This is mainly because the operating environment of the PEM is strongly acidic, placing higher demands on the corrosion resistance of the catalyst, even though a few catalysts have good stability in acid, often accompanied by surface restructuring during electrocatalysis. Therefore, it becomes difficult to reveal the structure-activity relationship of the catalyst, which is not favorable for the development and application of the catalyst. Currently, iridium-based oxides (IrO) 2 ) Still the most desirable catalyst in the PEM, even the only electrocatalyst considered in acidic OERs that may have reasonable catalytic activity and stability. However, iridium metal is a precious metal, and has a low earth reserve and a high price, which limits its large-scale application. Therefore, it is imperative to develop acidic OER catalysts with low noble metal Ir content while having high activity and stability.
The composite oxide is considered to be an effective way to reduce the amount of noble metal used and to increase the intrinsic activity of the metal. Perovskite (composite oxide containing a small amount of rare noble metal) enriches the types and the quantity of OER catalysts due to the flexible and adjustable structure, and the clear and specific crystal structure of perovskite can be generally used as a model catalyst to analyzeThe reaction mechanism is widely favored by researchers. For example, by Pulsed Laser Deposition (PLD) with SrTiO 3 As a substrate, 3C-SrIrO is deposited 3 The film shows good catalytic activity and stability under acidic conditions, and reduces the iridium content of the monolithic catalyst. Studies have shown that iridium species in high oxidation states (e.g., ir) 5+ Or Ir 6+ ) Proved to have better OER catalytic performance. However, it remains a challenge how to synthesize and stabilize high-valence Ir catalysts.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a novel catalyst material, a preparation method and application thereof.
In a first aspect of the invention, there is provided a novel catalyst material, la 2 IrO 6 And IrO 2 The hollow nano tubular structure with the heterojunction characteristic is formed by compounding, and is La containing high-valence iridium 2 IrO 6 /IrO 2 A heterojunction structure.
La 2 IrO 6 /IrO 2 IrO in a heterojunction structure 2 Can stabilize high valence La 2 IrO 6 Wherein two Ir are mutually adjustable, so that the iridium has a faster electron transfer rate, a suitable OH adsorption capacity and a faster deprotonation rate. [ the valence state, adsorption energy, etc. are described here, and whether experiments are needed below to support, the yellow part is a newly added part ]
By mixing La 2 IrO 6 /IrO 2 Ir 4f spectrum of and commercial IrO 2 The comparison of the spectrum of Ir 4f shows that La 2 IrO 6 /IrO 2 The middle Ir 4f has higher binding energy as a whole, and the valence state of Ir is higher, which indicates that La 2 IrO 6 /IrO 2 Has an iridium atom higher than +4, which also proves that the high valence iridium existing stably is successfully synthesized. For different catalysts, e.g. commercial IrO 2 Catalyst (IrO) 2 -C), irO produced by electrospinning 2 Nanowire (IrO) 2 -ES), and La provided by the present invention 2 IrO 6 /IrO 2 The polarization curve (LSV) test is performed, typically up to 10 mAcm -2 The overpotential at the current density was used to evaluate the catalyst activity. A lower overpotential represents a better catalytic activity of the catalyst. La 2 IrO 6 /IrO 2 The overpotential is the smallest among several catalysts, and is only 279 mV, which shows the best catalytic performance. While La 2 IrO 6 /IrO 2 Is also less than commercial IrO 2 This shows La 2 IrO 6 /IrO 2 Has good commercial application potential. Fitting the polarization curve to obtain a Tafel slope curve, la 2 IrO 6 /IrO 2 The tafel slope of (a) is minimal, indicating that La 2 IrO 6 /IrO 2 Has faster OER reaction kinetics, and is beneficial to the OER reaction. To La 2 IrO 6 /IrO 2 The intrinsic catalytic activity of the catalyst is studied, and La is calculated by an LSV curve 2 IrO 6 /IrO 2 Mass activity of La 2 IrO 6 /IrO 2 Has far better mass activity than commercial IrO 2 Catalyst, la at an overpotential of 300 mV 2 IrO 6 /IrO 2 Is about commercially available IrO 2 5 times as much as the catalyst, further demonstrating La 2 IrO 6 /IrO 2 Is potentially acidic OER catalytic.
Further, the La provided by the invention 2 IrO 6 /IrO 2 The catalyst material also exhibits excellent catalytic stability. For La by chronopotentiometry 2 IrO 6 /IrO 2 Was tested for stability of La 2 IrO 6 /IrO 2 At 10 mAcm -2 The continuous stable operation of the catalyst under the current density of (2) exceeds 80 h, the catalytic performance is hardly attenuated, and IrO 2 Under these conditions the performance drops dramatically for only a few hours.
Electrochemical impedance spectroscopy is also commonly used to probe the reaction mechanism of catalysts. EIS testing of the catalyst at OER potential (1.3V vs. Ag/AgCl), la 2 IrO 6 /IrO 2 Has a lower phase angle and shifts to high frequencies compared to IrO2-ES, indicating that La 2 IrO 6 /IrO 2 Has stronger adsorption capacity for the OER intermediate OH and has faster deprotonation rate in the OER reaction.
In conclusion, the La containing high-valence iridium provided by the invention 2 IrO 6 /IrO 2 The heterojunction structure shows excellent electrochemical activity and stability in the electrolytic water oxygen evolution reaction under the acidic condition, and is an oxygen evolution reaction catalyst with great potential.
In a second aspect of the present invention, there is provided a process for the preparation of the novel catalyst material as described above, comprising the steps of:
(1) Adding La (NO) 3 ) 3 ·6H 2 O and K 2 IrCl 6 Dissolving the precursor solution in a mixed solution of ethanol and N, N-dimethylformamide to obtain a precursor solution;
(2) Adding a spinning aid into the precursor solution to obtain a spinning solution;
(3) Spinning the spinning solution by an electrostatic spinning device to obtain La 2 IrO 6 /IrO 2 A LaOCl precursor;
(4) La 2 IrO 6 /IrO 2 Placing the LaOCl precursor in air for calcination to obtain La 2 IrO 6 /IrO 2 a/LaOCl nanotube;
(5) La obtained by calcining with hydrochloric acid 2 IrO 6 /IrO 2 Purifying the/LaOCl nanotube to obtain La 2 IrO 6 /IrO 2 The nano tube is the novel catalyst material.
The invention adopts an electrostatic spinning method to synthesize La 2 IrO 6 /IrO 2 The LaOCl precursor is purified by hydrochloric acid to remove the LaOCl impurities, so that pure La is obtained 2 IrO 6 /IrO 2 A catalyst. The purified sample is subjected to XRD analysis to find that IrO exists in the purified sample 2 Phase and the remaining diffraction peaks are also consistent with La reported in the literature 2 IrO 6 The diffraction peaks are consistent, indicating that La 2 IrO 6 /IrO 2 The catalyst material is successfully synthesized, the operation is simple and safe, the large-scale synthesis is easy, and the cost is saved.
Preferably, in step (1), la (NO) 3 ) 3 ·6H 2 O and K 2 IrCl 6 Is 1:1.
Preferably, in the step (2), the spinning aid is polyvinylpyrrolidone.
Preferably, in step (4), the calcination temperature is 750 ℃.
Preferably, in step (5), the hydrochloric acid treatment time is at least 16h.
In a third aspect of the present invention there is provided the use of a novel catalyst material as described above as a catalyst for an anode reaction. La 2 IrO 6 /IrO 2 The catalyst has high activity and high stability in acid oxygen precipitation, and has good application prospect.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the prior art descriptions will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is within the scope of the present invention for those skilled in the art to obtain other drawings based on the drawings without inventive labor.
FIG. 1: la 2 IrO 6 /IrO 2 Schematic diagram of nanotube synthesis;
FIG. 2: la 2 IrO 6 /IrO 2 XRD diffraction pattern of LaOCl;
FIG. 3: (a-b) La 2 IrO 6 /IrO 2 Low power and high power SEM images of/LaOCl, (c-f) La 2 IrO 6 /IrO 2 TEM and HRTEM image of bulk impurities on/LaOCl, (g-h) La 2 IrO 6 /IrO 2 TEM and HRTEM images of particles on/LaOCl tube wall, (i) La 2 IrO 6 /IrO 2 Element distribution image of/LaOCl;
FIG. 4 is a schematic view of: XRD diffractograms of samples at different hydrochloric acid treatment times;
FIG. 5: la 2 IrO 6 /IrO 2 An XRD pattern of (a);
FIG. 6: (a) La 2 IrO 6 /IrO 2 SEM image of (a), (b) La 2 IrO 6 /IrO 2 TEM image of (a), (c) La 2 IrO 6 /IrO 2 HRTEM image of (d) La 2 IrO 6 /IrO 2 The element distribution image of (1);
FIG. 7: la 2 IrO 6 /IrO 2 /LaOCl、La 2 IrO 6 /IrO 2 And commercial IrO 2 XPS spectra of Cl 2p and Ir 4 f;
FIG. 8: (a) Different materials are at 0.5 MH 2 SO 4 LSV curves in solution environment, all curves compensated by 90% iR, sweep rate 10 mVs -1 (ii) a (b) a tafel slope plot of the catalyst corresponding to the LSV curve;
FIG. 9: (a) Different materials are at 0.5 MH 2 SO 4 Mass-active LSV curves in solution environment, all curves compensated by 90% iR, sweep rate 10 mVs -1 ；（b）10 mAcm -2 A catalyst overpotential at current density and a catalyst mass activity histogram at 300 mV overpotential;
FIG. 10: measurement of La by chronopotentiometry 2 IrO 6 /IrO 2 Stability, catalyst is kept at 10 mAcm -2 Observing the voltage variation with time under the current density;
FIG. 11: (a-b) at 10, 20, 30, 40 and 50 mV s -1 Under the scanning speed of La, the La in the range of the non-faradaic capacitance current is not pulled 2 IrO 6 /IrO 2 And IrO 2 Cyclic voltammograms of ES, (c) fitting of current density differences to the scan rate. The linear slope corresponds to twice the double layer capacitance Cdl, used to represent ECSA;
FIG. 12: the initial current density of the multi-step current test is 10 mAcm -2 The terminal current density was 35 mAcm -2 Current density of 5 mAcm -2 The intervals of the lifting frames are uniformly lifted;
FIG. 13: (a) La 2 IrO 6 /IrO 2 And IrO 2 -ES Nyquist plot, (b) La 2 IrO 6 /IrO 2 And IrO 2 Phase diagram of ES at 1.3V.
Detailed Description
To make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings.
Example 1: la 2 IrO 6 /IrO 2 Preparation of catalyst materials
Preparing La by an electrostatic spinning method 2 IrO 6 /IrO 2 The hollow nanotube specifically comprises: 216.5 mg of La (NO) 3 ) 3 ·6H 2 O and 241.5 mg K 2 IrCl 6 (molar ratio 1:1) was dissolved in a mixed solution of 2 mL ethanol and 8 mL of N, N-dimethylformamide. Addition of 15 wt% PVP to the precursor solution after dissolution was complete increased the solution viscosity. The final spinning solution was then transferred to a syringe and clamped in a syringe pump. The voltage applied by the needle point is 20 kV, and the needle point (the injection rate of the injector is 0.6 mh) -1 ) The distance to the collector is 15 cm. The temperature of the whole system was maintained at 40 ℃. Calcining the film collected on the silicone oil paper in air at 750 ℃ to obtain La 2 IrO 6 /IrO 2 A LaOCl nanotube with a heating rate of 0.5 deg.C for min -1 . Purifying the calcined nanotube by using hydrochloric acid to obtain La 2 IrO 6 /IrO 2 A nanotube.
Example 2: la 2 IrO 6 /IrO 2 Catalyst Material characterization
An X-ray diffraction pattern was obtained by Cu ka radiation (40 kV, 100 mA, λ = 1.54056 a) using a D/MAX 2400 diffractometer; scanning electron microscope images were obtained using JSM-6700 (spot 3.0, 15 kV); transmission electron microscopy, high resolution transmission electron microscopy and energy dispersive X-ray spectroscopy were obtained using JEOL2100F (200 kV); high angle annular dark field electron microscopy was obtained by using FEI Themis Z.
La 2 IrO 6 /IrO 2 The synthetic scheme is shown in figure 1, calciningThe calcined electrostatic spinning precursor product is treated by hydrochloric acid to obtain pure La 2 IrO 6 /IrO 2 A catalyst. XRD was conducted on the catalyst precursor obtained by calcination, and as shown in FIG. 2, by comparing XRD diffraction peaks, it was found that the calcined material had a plurality of phase compositions containing La 2 IrO 6 、IrO 2 And LaOCl. By SEM characterization of the calcined product, as shown in fig. 3 (a-c), SEM and TEM results indicate that electrospinning was successful, with the precursor material exhibiting predominantly a tubular structure with the presence of particulate and bulk impurities, consistent with XRD results. To further investigate the composition of the precursor material, HRTEM analysis was performed on bulk impurities in the precursor material, as shown in fig. 3 (d-f), where the stripe pitch was 0.36 nm, consistent with the (101) crystal plane of LaOCl, indicating that the major composition of bulk impurities was LaOCl. The composition of the material attached to the nanotubes was also further explored, as shown in FIG. 3 (g-i), where the grain lattice stripe pitches attached to the tube wall were 0.32 nm and 0.26 nm, respectively, which is comparable to IrO 2 The (110) and (101) crystal planes of (A) are consistent, which shows that the particles attached to the tube wall are formed by IrO 2 And (4) forming. In combination with the above conclusions, it can be found that the precursor material is apparently not a single La 2 IrO 6 /IrO 2 A heterojunction structure. Therefore, we further propose a method of depurification treatment with hydrochloric acid to obtain La 2 IrO 6 /IrO 2 A heterojunction structure.
By varying the time of soaking the precursor material in hydrochloric acid, it was found that the hydrochloric acid treatment time is critical to the degree of purification of the precursor. XRD measurements were performed on samples of different hydrochloric acid treatment times, as shown in fig. 4, with the increase of treatment time, the diffraction peak signals at 2 θ angles of 12.8 °,30.7 ° and 34 °, respectively, appeared to be significantly decreased, indicating that the LaOCl content in the sample was significantly decreased during the hydrochloric acid treatment, and that the diffraction peak signals of LaOCl completely disappeared after the treatment time reached 16h, indicating that LaOCl was completely removed. To ensure complete removal of LaOCl, samples treated with hydrochloric acid for 20h were taken for subsequent studies.
When XRD analysis was performed on the purified sample, irO was found to be present in the purified sample as shown in FIG. 5 2 Phase and the remaining diffraction peaks are also consistent with La reported in the literature 2 IrO 6 The diffraction peaks are consistent, indicating that La 2 IrO 6 /IrO 2 The catalyst material was successfully synthesized.
To further explore the structure of the purified catalyst, la 2 IrO 6 /IrO 2 SEM and TEM of the catalyst are shown in FIG. 6 (a-b), la 2 IrO 6 /IrO 2 The catalyst is represented by a smooth nano-tubular structure, and La is treated by 2 IrO 6 /IrO 2 HRTEM analysis showed that the lattice fringe spacings were 0.278 nm, 0.256 nm and 0.319 nm for La 5363, respectively, as shown in FIG. 6 (c) 2 IrO 6 Crystal plane of (112) and IrO 2 (101) and (110) crystal planes of La 2 IrO 6 And IrO 2 A distinct heterojunction interface exists between the two, and the catalyst is a catalyst with heterojunction characteristics. Further, la 2 IrO 6 /IrO 2 The distribution of the elements (b) in (c) is shown in fig. 6 (d), indicating that the La, ir, and O elements are uniformly distributed in the catalyst. To confirm the purification of para-La by hydrochloric acid treatment 2 IrO 6 /IrO 2 Influence of electronic Structure on La 2 IrO 6 /IrO 2 XPS test was performed, and as shown in FIG. 7, la was compared with the sample which had not been treated with hydrochloric acid 2 IrO 6 /IrO 2 The signal of Cl 2p is completely disappeared, which indicates that the catalyst does not contain chlorine element, and the result is consistent with the XRD result, and the obvious effect of the hydrochloric acid purification treatment on the removal of LaOCl is proved. Further, la 2 IrO 6 /IrO 2 Compared with the sample before purification, the position of the Ir 4f spectrogram is not shifted, which indicates that the hydrochloric acid treatment does not change La 2 IrO 6 /IrO 2 Structural properties of (a). Simultaneously by passing La 2 IrO 6 /IrO 2 Ir 4f spectrum of and commercial IrO 2 By comparing the obtained Ir 4f spectrogram, la 2 IrO 6 /IrO 2 The middle Ir 4f has higher binding energy as a whole, and the valence state of Ir is higher, which indicates that La 2 IrO 6 /IrO 2 Has more than 4+ iridium atom, which also proves that the high valence iridium atom which exists stably is successfully synthesized.
Example 3: la 2 IrO 6 /IrO 2 Electrochemical testing of catalyst materials
All electrochemical tests presented in this work were at 0.5 mh 2 SO 4 The test is finished in a solution environment, and all instruments used in the test are Shanghai Chenghua CHI 760E. In the three-electrode system used for the test, the counter electrode was a platinum sheet electrode, the working electrode was carbon paper coated with a catalyst material, the size was 0.5 cm × 2 cm, and the calomel electrode was used as a reference electrode (SCE). In all electrochemical tests, E was passed vs.RHE = E vs.SCE + 0.264V converts the electrode potential to a Reversible Hydrogen Electrode (RHE).
When the working electrode is prepared, weighing 4 mg catalyst material and a 1.5 ml centrifuge tube, adding 1 mL deionized water, carrying out ultrasonic treatment for 30 min to obtain uniformly dispersed turbid liquid, sucking 10 mu L of uniformly dispersed turbid liquid through a liquid transfer gun, dripping and coating the uniformly dispersed turbid liquid on the tail end of carbon paper, drying in a drying box, coating 5 mu L of 0.2% Nafion solution again, and drying again to obtain the working electrode. Through calculation, the working electrode catalyst load used in the work is 0.56 mg cm -2 。
In electrochemical tests, the linear voltammogram passes at 10 mvs -1 Obtaining the scanning speed of the scanning unit, and performing 90% of iR compensation correction on each curve; the cyclic voltammograms in the electrochemically active area are respectively 10, 20, 30, 40, 50 mv s -1 Is obtained under the sweeping speed condition of (1); the frequency range of electrochemical impedance spectroscopy measurement is 100 kHz to 0.01 Hz, the potential is 1.3V, and the amplitude potential is 5 mV. The current density of the catalyst test in the chronovoltmeter method is 10 mA cm -2 。
In a conventional three-electrode system, a series of electrochemical performance tests were performed on the catalyst. First on different catalysts such as commercial IrO 2 Catalyst (IrO) 2 -C), irO produced by electrospinning 2 Nanowire (IrO) 2 -ES), and La 2 IrO 6 /IrO 2 The polarization curve test is carried out, and usually 10 mAcm is reached -2 The overpotential at the current density was used to evaluate the catalyst activity. A lower overpotential represents a better catalytic activity of the catalyst.
La as shown in FIG. 8 (a) 2 IrO 6 /IrO 2 The overpotential is the smallest among several catalysts, and is only 279 mV, which shows the best catalytic performance. While La 2 IrO 6 /IrO 2 Is also less than commercial IrO 2 This shows La 2 IrO 6 /IrO 2 Has good commercial application potential. The Tafel slope curve can be obtained by fitting the polarization curve, as shown in FIG. 8 (b), la 2 IrO 6 /IrO 2 The tafel slope of (a) is minimal, indicating that La 2 IrO 6 /IrO 2 Has faster OER reaction kinetics, and is beneficial to the OER reaction. To La 2 IrO 6 /IrO 2 The intrinsic catalytic activity of the catalyst is studied, and La is calculated by an LSV curve 2 IrO 6 /IrO 2 The mass activity of (a) is shown in FIG. 9 (a-b), la 2 IrO 6 /IrO 2 Has far better mass activity than commercial IrO 2 Catalyst, la at an overpotential of 300 mV 2 IrO 6 /IrO 2 Has a mass activity of about commercial IrO 2 5 times as much as the catalyst, further demonstrating La 2 IrO 6 /IrO 2 Is potentially acidic OER catalytic. La 2 IrO 6 /IrO 2 The catalyst not only has excellent acidic OER catalytic activity, but also shows excellent catalytic stability. As shown in FIG. 10, the chronopotentiometry was applied to La 2 IrO 6 /IrO 2 Was tested for stability of La 2 IrO 6 /IrO 2 At 10 mAcm -2 The current density of the catalyst exceeds 80 h continuously and stably, the catalytic performance is hardly attenuated, and the IrO 2 Under these conditions the performance drops dramatically for only a few hours. From this, la can be demonstrated 2 IrO 6 /IrO 2 Not only has excellent OER catalytic activity, but also has excellent OER catalytic stability, which indicates that La 2 IrO 6 /IrO 2 Is oxygen evolution with great potentialA reaction catalyst.
Based on electrochemical cyclic voltammetry, the electrochemical active specific surface area of all the catalysts is evaluated through electrochemical double-layer capacitance, so that the specific surface area of the catalyst is opposite to that of La 2 IrO 6 /IrO 2 The reason for the excellent catalytic activity is briefly disclosed. As shown in FIG. 11 (c), la 2 IrO 6 /IrO 2 Has an electrochemical active area higher than that of IrO 2 ES, stating that La is used in the OER reaction 2 IrO 6 /IrO 2 More active sites are exposed. And in the multi-step amperometric test of FIG. 12, la 2 IrO 6 /IrO 2 As the current density was increased stepwise, the overpotential was also uniformly increased, indicating that La 2 IrO 6 /IrO 2 Also has excellent charge transfer kinetics.
Electrochemical impedance spectroscopy is also often used to explore the reaction mechanism of catalysts. EIS testing was performed on the catalyst at OER potential (1.3V vs. Ag/AgCl), as shown in FIG. 12 (a). By analyzing the Nyquist diagram, la in a low-frequency region can be found 2 IrO 6 /IrO 2 Has a smaller charge transfer resistance (Rct), indicating that La 2 IrO 6 /IrO 2 Faster charge transfer kinetics; in the high frequency region La 2 IrO 6 /IrO 2 Also has faster diffusion kinetics. Further, as shown in FIG. 12 (b), EIS phase diagram was analyzed, la 2 IrO 6 /IrO 2 And IrO 2 Has a lower phase angle and shifts to higher frequencies than ES, indicating La 2 IrO 6 /IrO 2 Has stronger adsorption capacity for the OER intermediate OH and has faster deprotonation rate in the OER reaction.
The above disclosure is only for the purpose of illustrating the preferred embodiments of the present invention, and it is therefore to be understood that the invention is not limited by the scope of the appended claims.
Claims (7)
1. A novel catalyst material characterized by: it is La 2 IrO 6 And IrO 2 Composite shapeThe hollow nano-tube structure with the heterojunction characteristic is formed.
2. The method for preparing a novel catalyst material according to claim 1, characterized by comprising the steps of:
(1) Adding La (NO) 3 ) 3 ·6H 2 O and K 2 IrCl 6 Dissolving the precursor solution in a mixed solution of ethanol and N, N-dimethylformamide to obtain a precursor solution;
(2) Adding a spinning aid into the precursor solution to obtain a spinning solution;
(3) Spinning the spinning solution by an electrostatic spinning device to obtain La 2 IrO 6 /IrO 2 A LaOCl precursor;
(4) La 2 IrO 6 /IrO 2 Calcining LaOCl precursor in air to obtain La 2 IrO 6 /IrO 2 a/LaOCl nanotube;
(5) La obtained by calcining with hydrochloric acid 2 IrO 6 /IrO 2 Purifying the/LaOCl nanotube to obtain La 2 IrO 6 /IrO 2 A nanotube.
3. The method for preparing a novel catalyst material according to claim 2, characterized in that: in step (1), la (NO) 3 ) 3 ·6H 2 O and K 2 IrCl 6 Is 1:1.
4. The method for preparing a novel catalyst material according to claim 2, characterized in that: in the step (2), the spinning aid is polyvinylpyrrolidone.
5. The method for preparing a novel catalyst material according to claim 2, characterized in that: in the step (4), the calcination temperature is 750 ℃.
6. The method for preparing a novel catalyst material according to claim 2, characterized in that: in the step (5), the hydrochloric acid treatment time is at least 16h.
7. Use of the novel catalyst material according to claim 1 as catalyst for anodic oxygen evolution reactions.
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