Theoretical Research On Water Splitting Reaction Mechanism Catalyzed By The TiO₂ And Doped Semiconductor Photocatalytic Materials

In recent years,the energy shortage crisis and environmental pollution have been intensified.Developing renewable energy is an effective way to relieve the present situation.Hydrogen is a non-toxic,harmless and high calorific value gas.The only product after hydrogen combustion is water,which is non-toxic by-product and environmentally friendly.Because of these advantages,hydrogen can be considered as one of the ideal green energy sources.One of the keys to the development of hydrogen energy is whether hydrogen can be prepared economically and efficiently.In recent years,research on hydrogen production by hydrolysis has focused on the optimization of catalyst preparation,the catalytic effect of photocatalyst and electrocatalyst,and how to improve the utilization of visible light of semiconductor photocatalytic materials.However,current research on hydrogen production by hydrolysis is insufficient in catalytic activity and kinetics.The paper studied the pristine and doped anatase TiO₂?001?and?101?catalyst surfaces model,and optimized the catalyst stable structure using Materials Studio software.The energy gap,density of states and electronic density of the catalyst were studied.The utilization of visible light and the light absorption effect of the series of catalysts were analysised according to the calculated energy gap value.At the same time,the paper studied the adsorption characteristics of reactants,intermediates and products on the surface of the catalyst during hydrogen production by water splitting.The adsorption energies of H₂O,H,OH^-and H₂ on the surface of the catalyst were calculated.At the same time,the catalytic poisoning and deactivation were analysised based on the adsorption energy of H₂O,OH^-and H₂ on the catalyst surface.This paper studied the adsorption energy of reactants,intermediates and products in the process of hydrogen production in a stable catalytic model,compared the adsorption energy of different adsorption sites.The first part of the paper focuses on the physical properties and adsorption properties of the catalytic model.During the electrochemical hydrylysis reaction for hydrogen production,H₂O in the solution is conducted to the surface of the catalytic electrode by diffusion and convection,and the Volmer reaction occurs:M+H₂O+e?M-H_ads+OH^-.The catalyst M reacts with H₂O,H₂O is decomposed and released OH^-and H.The hydrogen atom is adsorbed on the catalyst M to form M-H_ads.M-H_ads may desorb hydrogen by two different ways.One is through Heyrovsky reaction:M-H_ads+H₂O+e?M+H₂?+OH^-;the other is through Tafel reaction:M-H_ads+M-H_ads?2M+H₂?.The hydrogen generated by the reaction accumulates continuously on the surface of catalyst M,and finally forms a bubble escaping solution.There are two general mechanisms of hydrogen evolution reaction:Volmer-Heyrovsky mechanism and Volmer-Tafel mechanism.This paper studied the kinetic processes of hydrogen production from water catalyzed by series catalysts according these mechanisms.The mechanism of catalytic reaction was studied,the activation energies of catalytic reaction in different processes were calculated,and the activity of the constructed catalyst for hydrogen production by hydrolysis was investigated.This paper also studied the catalytic activity of the series catalysts in excited electronic.Pristine catalyst was selected to study catalytic performance in the external electric field.It was found that the applied electric field can effectively reduce the activation energy of the catalytic reaction and increase the activity of the catalyst.