Microenvironment Regulation And CO₂/O₂ Related Electrocatalytic Properties Of Single-Atom/Nano Materials

The coordination environment surrounding the active center affects the catalytic activity,selectivity and stability of electro-catalysts seriously.In recent years,efficient catalyst with well-defined structure has been prepared by the atomically regulation of coordination environment,including heteroatom doping,the change of coordination number,type of ligand and coordination direction.At the same time,the research strategy for synthesizing electro-catalysts with better catalytic performance was also offered.This thesis focus on the atomically coordination environment regulation of active sites on the surface of nanomaterials.The purpose is to prepare highly efficient electro-catalysts,find out low-cost preparation methods for catal ysts,utilize effective characterization methods and theoretical calculation for discovering coordination environment structure of active sites and clarify the structure-activity relationship between the coordination environment of active sites and catalyt ic performance.By using the strategy of fast-pyrolyzing and controllable-activation strategy,Fe N₄-O₁ site was successfully designed and constructed by inducing the coordination between the precursor containing Fe N ₄ sites and N、O co-doped carbonaceous support.The coordination structure of Fe N₄-O₁ active sites were verified by a variety of characterization techniques.Catalytic performance test shows that the FE_CO can be continuously maintained at a high level of nearly 100%under a wide potential range in the presence of catalysts containing Fe N ₄-O₁active sites.First-principle density functional theory（DFT）calculations revealed that,compared with Fe N₄ and Fe N₄-N₁ sites,the axial O ligand in Fe N₄-O₁ sites consume the electron density in Fe 3d orbitals,promotes the rapid desorption of CO,improves the selectivity of CO and inhibits the competitive hyd rogen evolution reaction.It is the fundamental reason for the highly efficient catalytic performance in the CO₂ electro-reduction reaction.CoN₄-S₁ sites modified by axial Co-S bond were successfully designed and synthesized using matrix-activization combined with controlled induction strategy.The coordination structure of Co N ₄-S₁ active sites were confirmed by a variety of advanced characterizations.The catalyst containing Co N₄-S₁ sites showed excellent electro-catalytic performance.Moreover,the Zinc-Air battery with catalyst containing Co N₄-S₁ site as negative electrode displays excellent catalytic activity and stability.According to the experi mental data and theoretical calculation results,we confirm that the axial Co-S bond can effectively promote the regulation of the electronic structure of the Co central site,and thus improve the catalytic ability of oxygen reduction reaction.A series of Ru based oxide catalysts with Mn-doped and metal defects were prepared by molten salt method with adjusting the amount of Mn element.The existence of metal defects on the catalyst surface and the successful doping of Mn in the crystal structure of Ru based oxide catalyst were verified by characterization methods.It could be found that the doping of Mn element can both improve the activity and stability of Ru based oxide to catalyst oxygen evolution reaction in acidic solution.Based on the theoretical ca lculation,it is found that Mn doping can reduce the valence electrons of Ru site,which is beneficial to the formation of O₂,and decrease the energy barrier of rate-determining step of Ru based oxide catalyst in acidic oxygen evolution reaction.