Preparation Of New Multi-component Iridium Oxide Electrocatalysts And Investigation Of Their Oxygen Evolution Performance

The problem of environmental pollution caused by the use of fossil fuels is becoming increasingly severe,and hydrogen energy is receiving significant attention.Proton exchange membrane water electrolysis(PEMWE)is an effective method for producing green hydrogen.However,the high overpotential caused by the four-electron transfer oxygen evolution reaction(OER)is the main factor limiting the efficiency of water electrolysis.Moreover,at high industrial current densities,the anode catalyst of the PEM electrolysis cell is in a strong oxidative and acidic environment,requiring high stability of the catalyst.Currently,commercial OER catalysts mainly focus on the precious metal IrOx,but their high loading makes it difficult to meet the demands of large-scale commercial applications.Therefore,the development of efficient,stable,and costeffective iridium based OER catalysts has significant theoretical and practical significance.The following research results have been achieved:(1)A nanocatalyst with a core-shell structure of Sb0.3Ir0.7Ox@TB-IrOx,rich in twin boundaries,was prepared and showed excellent OER catalytic activity(100 mA cm-2,η=270 mV).Moreover,the catalyst also exhibited a mass activity of 3.16 A mgIr-1(η=270 mV),which is 26.17 times higher than that of commercial iridium oxide.The catalyst operated for 100 hours with a potential increase of only 10 mV.Through characterization techniques such as X-ray absorption spectroscopy and density functional theory calculations,it was demonstrated that the strain and doping caused by the twin boundaries together shifted the Ir 5d band center(εd)towards the Fermi level,enhancing its adsorption energy for oxygen intermediates.(2)On the basis of Sb-doped IrOx,a core-shell structured nanocatalyst of three metals,Tm0.iSb0.2Ir0.7Ox@TB-IrOx,was prepared and showed even better OER catalytic performance(100 mA cm-2,η=262 mV).The catalyst also exhibited a mass activity of 3.36 A mgIr-1(η=270 mV),which is 27.80 times higher than that of commercial iridium oxide,and only had a potential increase of 6 mV after operating for 100 hours.PEM electrolysis experiments showed that the cell voltage at 2.0 A cm-2 was 2.011 V,and the efficiency did not significantly decay after 200 hours of operation.Density functional theory calculations demonstrated that under the synergistic effect of strain and doping caused by the twin boundaries,the adsorption energy of oxygen intermediates was enhanced.The introduction of Tm caused the Ir 5d band center(εd)to be closer to the Fermi level,which made it exhibit higher OER catalytic activity.Theoretical calculations also showed that the distance change between the p band center of O 2p and the Ir 5d band center was small,confirming that the covalency between metals and oxygen in the catalyst was enhanced,which resulted in its excellent stability.(3)On the basis of single-metal doping,an optimized catalyst was loaded onto a metal oxide carrier to prepare the Sb0.3Ir0.7Ox@TB-IrOx/Sb0.2Sn0.8O2 nanocatalyst,which exhibited excellent OER catalytic performance(100 mA cm-2,η=249 mV).It is worth noting that the catalyst showed a high quality activity of 4.07 A mgIr-1(η=270 mV),which is 33.62 times that of commercial iridium oxide,and achieved 100 h of electrode potential stability(increased by only 3 mV).PEM electrolysis experiments showed that its cell voltage at 2.0 A cm-2 was 1.997 V,and its performance did not show significant decay during 200 hours of operation.The catalyst particles on the carrier have a smaller particle size(3 nm),which results in a larger electrochemical active surface area of the catalyst.This indicates that the active sites of the catalyst are fully exposed,promoting the OER reaction rate and exhibiting better OER catalytic performance.This thesis aims to develop high-quality and highly stable Ir-based catalysts for the OER field in PEM electrolysis cells.A series of multi-element iridium oxide catalysts were prepared by doping stable metallic elements into IrOx and loading them onto a metal oxide support to regulate the electronic structure of the catalyst and investigate the influence of the electronic structure of the metal catalyst elements.