Mixed iridium-nickel oxides supported on antimony-doped tin oxide as highly efficient and stable acidic oxygen evolution catalysts

Proton exchange membrane(PEM)water electrolysis represents a promising technology for green hydrogen production,but its widespread deployment is greatly hindered by the indispensable usage of platinum group metal catalysts,especially iridium(Ir)based materials for the energy-demanding oxygen evolution reaction(OER).Herein,we report a new sequential precipitation approach to the synthesis of mixed Ir-nickel(Ni)oxy-hydroxide supported on antimony-doped tin oxide(ATO)nanoparticles(IrNiyO_(x)/ATO,20 wt.%(Ir+Ni),y=0,1,2,and 3),aiming to reduce the utilisation of scarce and precious Ir while maintaining its good acidic OER performance.When tested in strongly acidic electrolyte(0.1 M HClO_(4)),the optimised IrNi1Ox/ATO shows a mass activity of 1.0 mAµgIr^(−1) and a large turnover frequency of 123 s^(−1) at an overpotential of 350 mV,as well as a comparatively small Tafel slope of 50 mV dec^(−1),better than the IrOx/ATO control,particularly with a markedly reduced Ir loading of only 19.7µgIr cm^(−2).Importantly,IrNi1O_(x)/ATO also exhibits substantially better catalytic stability than other reference catalysts,able to continuously catalyse acidic OER at 10 mA cm^(−2) for 15 h without obvious degradation.Our in-situ synchrotron-based x-ray absorption spectroscopy confirmed that the Ir^(3+)/Ir^(4+)species are the active sites for the acidic OER.Furthermore,the performance of IrNi1Ox/ATO was also preliminarily evaluated in a membrane electrode assembly,which shows better activity and stability than other reference catalysts.The IrNi1Ox/ATO reported in this work is a promising alternative to commercial IrO_(2) based catalysts for PEM electrolysis.

Improving the Catalytic Efficiency of NiFe-LDH/ATO by Air Plasma Treatment for Oxygen Evolution Reaction

Developing efficient catalysts toward the oxygen evolution reaction(OER)is important for water splitting and rechargeable metal-air batteries.Although NiFe oxides are considered as potentially applicable catalysts in the alkaline media,there are still a limited numbers of researches working on membrane electrode assembly(MEA)fed with pure water due to their poor electrical conductivity.In this work,antimony doped tin oxide(ATO)has been employed as conductive supports where NiFe layered double hydroxide uniformly dispersed[named NiFe-LDH(layered double hydroxide)/ATO].The catalysts have been synthesized by a one-step co-precipitation method,and then NiFe-LDH/ATO-air plasma was obtained through mild air plasma treatment.According to XPS analysis,binding energies of Ni2p and Fe2p were shifted negatively.Moreover,a new signal of low oxygen coordination appeared on O1s spectrum after air plasma treatment.These XPS results indicated that oxygen vacancies(Ov)were generated after air plasma treatment.Electrochemical measurement indicated that the vacancy-rich NiFe-LDH/ATO-air plasma exhibited better performance than NiFe-LDH/ATO not only in 1 mol/L KOH solutions but also in an alkaline polymer electrolyte water electrolyzer(APEWE)fed with deionized water.This work provides a feasible way to design practical catalysts used in electrochemical energy conversion systems by choosing corrosion resistance supports and defect engineering.