Based On The First Principles, The Co-doped Graphene And Titanium Dioxide-based Single-atom Electrocatalytic Reaction Were Designed

The electrocatalytic reaction plays an important role in the electrochemical energy storage and conversion system,but the slow dynamics in the process has hindered the wide use of energy storage equipment.So far,Pt based nanomaterials are the most excellent electrocatalysts,but their content is scarce and expensive,which greatly restricts the wide application of energy storage and conversion systems at the core of electrocatalysis.Therefore,it is urgent to find non-Pt based catalysts with high catalytic activity and cyclic stability.In recent years,heteroatom doped graphene and titania based monatomic materials have been widely studied because of their good electrocatalytic activity.Among them,the doping of N,P,S and other atoms is the most concerned.Mainly because the doping of the heteroatom can produce defects in the base surface of the graphene,opening the band gap of the perfect graphene,and thus improving its electrochemical performance.For the titanium dioxide based single atom material,the Ti O2（B）bandgap is reduced by the load of the single atom,and the electrical conductivity of the structure is enhanced,and its electrocatalytic performance is also improved.In this paper,the structure and electronic properties of the doped graphene and titanium dioxide based single atom are systematically studied.Based on the first principle,the influence of doping and load on the electrocatalytic reaction is deeply explored.The oxygen reduction reaction（ORR）,hydrogen evolution reaction（HER）and CO₂ reduction reaction（CO₂RR）pathways of tri doped graphene catalysts（Ge,N,P）were studied in detail by density functional theory（DFT）,and the effect of solvent effect was considered.The electronic structure of the doped graphene analyzed by differential charge density diagram,formation enthalpy,density of state（DOS）and Bader charge analysis,and the reaction path of the design model is analyzed by the adsorption energy of the type of intermediate adsorption.It is found that in the case of solvent effect,the hydrogen bond of water molecules helps to adsorb the intermediate products,reduces the energy barrier of the reaction kinetics and improves its adsorption capacity.Meanwhile,according to Gibbs free energy diagram,tri-doped graphene shows a small overpotential,which is significantly less than that of binary doped graphene materials.Therefore,（Ge,N,P）tri-doped graphene material exhibit the excellent catalytic performance for ORR.On the basis of theoretical calculation,we have successfully doped（Ge,N,P）into graphene by high temperature calcination,and synthesized Ge-N-P-r GO catalysts.Element distribution（EDS mapping）,X-ray photoelectron spectroscopy（XPS）and other characterization methods were used to characterize the surface composition and chemical bonds of the catalyst.The catalytic activity of the catalyst was measured by linear sweep voltammetry.The results show that the catalytic activity of tri-doped graphene is obviously better than that of co-doped graphene.The limiting current density,onset voltage and half wave voltage of Ge-N-P-r GO are very close to commercial Pt/C catalysts.In addition,we systematically study the CO₂ RR catalytic reaction of titanium dioxide based single atom,mainly through the analysis of the electronic structure according to the differential charge,DOS,Bader charge and so on.At the same time,the free energy diagram is drawn to explain the catalytic performance of the CO₂ RR.Because of the different pathways will produce different products,we designed six kinds of metal atom loaded Ti O2（B）matrix to obtain the desired target product.