Application Of Ion Beam To The Interface And Defect Regulation Of Metal Oxide In Water Splitting Catalyst

Hydrogen energy is considered to be an ideal energy carrier to replace fossil energy due to its advantages such as clean,renewable,high energy density,and pollution-free reaction products.The use of solar energy to produce hydrogen energy has brought new dawn for further solving the energy crisis and environmental pollution.At present,photovoltaic-electrocatalytic water splitting and photoelectrochemical water splitting systems have shown great application prospects and development potential.However,due to the large energy barrier and slow reaction kinetics of the oxygen-producing halfreaction during the water splitting reaction process,the reaction efficiency of the oxygen evolution electrode in the photovoltaic-electrocatalytic water splitting system and the photoanode in the photoelectrochemical water splitting system is pretty low,which greatly limits the further industrial application of solar water splitting to produce hydrogen.Therefore,the preparation of highly catalytically active non-noble metal oxygen-producing photoelectrode materials and electrocatalytic oxygen-producing electrode materials is extremely important and urgently.Transition metal oxide semiconductors(Ti O2,Fe2O3,WO3,etc.)have been widely studied for photoelectrochemical water splitting photoanode materials due to their relatively suitable energy band width and relatively stable photoelectrochemical stability.At the same time,some other transition metal oxides(Ni O,Co3O4,etc.),due to their high dband electron activity,have shown excellent catalytic activity in electrocatalytic oxygen production reactions.Therefore,the modification of transition metal oxides to greatly improve the catalytic activity of water splitting is one of the problems that must be solved to achieve solar energy production of hydrogen energy.In recent years,the defects and interface regulation of catalysts have been widely concerned by researchers.On the one hand,defects and interfaces can affect the optical and electrical properties of the material itself(band width,carrier separation and injection efficiency,carrier density,density of state band center,conductivity,etc.)can effectively improve the photoelectric or electrocatalytic performance of the material;on the other hand,defects and interface generation can expose new catalytically active sites or become more active reaction sites.Traditional techniques such as thermal annealing in a reducing atmosphere,plasma etching,chemical vapor deposition and other methods have been widely studied and have shown excellent results,greatly improving people's understanding of defects and interface regulation.However,on this basis,the development of a more controllable,better repeatable defects and interface preparation methods are still challenging and significant.As an industrial surface modification technology,ion beam technology can effectively introduce heteroatoms,defects and even induce phase changes in materials through precise adjustment of implantation energy and dose.This provides us with new method for modifying photoelectric catalysts and electrocatalysts,as well as in-depth study of the reaction mechanism,and does the following work.(1)For the photoelectrochemical water splitting photoanode material ?-Fe2O3,we use a novel and efficient ion implantation of Au element and annealing method to significantly improve the efficiency of ?-Fe2O3 photoelectrochemical water splitting.The analysis revealed that oxygen vacancies and intimately Au/ Fe2O3 interface were generated in the Au-implanted ?-Fe2O3 sample.Therefore,the carrier separation efficiency and injection efficiency of the Au-implanted ?-Fe2O3 sample were significantly improved.The photocurrent density of the sample can reach 1.16 m A/cm2 at 1.5 V vs.RHE,which is nearly 300 times(4 ?A/cm2)higher than the pristine sample photocurrent density.In addition,Au-implanted ?-Fe2O3 samples showed little photocurrent decay during the 8-hour photoelectrochemical water splitting test,and showed good stability.(2)For the electrocatalytic oxygen evolution reaction(OER)material Co3O4,we irradiate Co3O4 with Ar ions of different energies to induce phase transition to prepare samples with Co O/Co3O4 heterogeneous interface in situ,and samples with a large amount of oxygen vacancies.X-ray photoelectron spectroscopy,X-ray absorption spectroscopy,UV photoelectron spectroscopy,and density functional theory calculations together proved that the active electron state density center of Co3O4 was gradually increased,thereby greatly enhancing the surface adsorption capacity for the oxo groups during the reaction process.Therefore,the best prepared sample exhibited excellent electrocatalytic oxygen generation performance,which showed an overpotential of reached 10 m A/cm2 reaction current and a Tafel slope of 260 m V and54 m V/dec,respectively.This performance is superior to commercial Ru O2,and is one of the best Co-based oxygen evolution reaction catalysts.In addition,this opinion of adjusting the density of states of active electronic provides us with a new perspective to understand the electrocatalytic mechanism of Co-based oxide catalysts,thus guiding us to design and synthesize and discover more excellent electrocatalysts.(3)At the same time,we extend the method of Ar ion irradiation to the modification of other metal oxides such as Mn O2,Ni O,etc.We used high-energy Ar ions irradiated Mn O2 firstly,XANES test proved that oxygen vacancies can be effectively introduced into Mn O2,thereby improving its conductivity,so the overpotential required for this sample to reach 20 m A/cm2 is only 220 m V,which is far better than commercial Ru O2 and original Mn O2.Further experimental results show that Ar ion irradiation can also effectively modify OER performance of Ni O.It shows that the method of ion irradiation has the possibility of developing into a universal electrocatalyst modified method.