Investigation Of Photoelectric Catalytic Energy Conversion Based On Field-effect

Photo/electrocatalytic splitting of water（H₂O）to produce hydrogen（H₂）and reduction of carbon dioxide（CO₂）to prepare hydrocarbon fuels is one of the potential technologies to solve the energy crisis and carbon emissions.In hydrogen evolution reaction（HER）,problems such as high overpotential and low current density severely limit the practical application of photo/electrocatalytic hydrogen production;meanwhile,in CO₂ reduction（CO₂RR）,the problems of poor catalytic activity and low product selectivity It also hinders the process of CO₂resource utilization.In the process of these catalytic reactions,the introduction of light fields,electric fields,etc.can induce field-effect,change the intrinsic activity of catalysts and the local micro-environment of catalytically active sites,and become an effective means to optimize overpotential,current density,and control reaction activity and selectivity.Field-effect can affect electronic excitation,photogenerated charge separation,reactant molecular adsorption,and local reactant concentrations during electrode reactions.In this paper,by constructing an external light field,an interfacial electric field and a local electric field,the role of the field-effect in the electrocatalytic hydrogen production and photocatalytic CO₂ reduction reaction was explored,which provided a reference for in-depth understanding of the relationship between the field effect and the catalytic performance.The specific research contents are as follows:（1）Ag/Mo₂C was selected as the model catalyst to explore the influence of the hot electrons excited by the light field effect on the surface of metallic Ag on the photoelectric catalytic hydrogen production activity.Finite element simulation（FEM）and Kelvin probe force microscopy（KPFM）proved that the Ag/Mo₂C structure can excite hot electrons on the surface of Ag particles.Hot electrons will reduce the activation energy,and the photoelectron catalytic hydrogen evolution overpotential of sample Ag/Mo₂C is reduced by 104 m V compared with Mo₂C.（2）The Schottky junctions constructed by metallic MoO₂ and g-C₃N₄were used as model catalysts to explore the effect of the interfacial electric field between MoO₂ and g-C₃N₄ on the photocatalytic CO₂ reduction activity and selectivity by promoting the separation of photogenerated charges.Density functional theory（DFT）calculations and experiments have proved that there is an interfacial built-in electric field between MoO₂/g-C₃N₄ Schottky junctions,and transient fluorescence spectroscopy proves that the interfacial built-in electric field can accelerate the separation of photogenerated charges,thereby enhancing CO₂ reduction activity and selective.The photocatalytic CO₂ reduction performance test showed that the CO and CH₄ yields obtained on MoO₂/g-C₃N₄ were 5 times and 15 times higher than those of pure g-C₃N₄,respectively.（3）Ru/MoO₂ was selected as the model catalyst to explore the effect of the Ru-O-Mo interfacial electric field on the activity of alkaline electrocatalytic hydrogen production by inducing the adsorption of reactant molecules.The Ru-O-Mo interface was found to have stronger water adsorption energy and lower water dissociation energy barrier using density functional theory（DFT）calculations,and the Ru-O-Mo interface and charge transfer were determined by synchrotron radiation and photoelectron spectroscopy The existence of,further confirmed by infrared and water sensor tests that the Ru-O-Mo interface electric field has stronger water adsorption energy.The hydrogen production performance of alkaline water electrolysis shows that the overpotential of Ru-O-Mo interface catalyst is only 16 m V,and its stability can reach 40 h.（4）Ni/Mo-Ni with a protruding structure was selected as the model catalyst to explore the effect of the local electric field formed by the protruding structure on the electrocatalytic total water splitting activity by causing the local reactant concentration change.Finite element simulations and ion adsorption experiments demonstrate that the raised Ni particle surfaces in the Ni/Mo-Ni structure form a local electric field,which can affect the local reactant concentration and mass transfer,thereby improving the activity of the catalyst.Electrocatalytic water splitting tests show that the Ni/Mo-Ni overpotential is only 25 m V in hydrogen production and 215m V in oxygen production reaction,and in total water splitting test,only1.76 V is required to drive 100 m A cm^-2 current density.