Catalysts With D-sp Orbital Hybridization: Computational Screening And Electronic Structure

For heterogeneous catalysts,the electronic structure of surface is crucial for their chemisorption and catalytic reaction properties.The electronic interaction between transition metals and light elements,that is,d-sp orbital hybridization,has been proved to break the bottleneck of the activity and selectivity of some transition metal-based catalysts.However,most of the reported catalysts with d-sp orbital hybridization are amorphous,which does not possess well-defined crystal structure.Therefore,it is difficult to reveal the relationship between structure and catalytic activity.In addition,the synthesis of catalysts with d-sp orbital hybridization which possesses well-defined structure is usually carried out under harsh reaction conditions.It is difficult to obtain a pure crystal phase.Combining theory and experiment,we take catalysts with d-sp orbital hybridization which possess well-defined crystal structures as research models,and studied the effects of d-sp orbital hybridization on the electronic structure and adsorption properties of catalysts.We are the first to put forward the concept of catalysts with d-sp orbital hybridization.Our results presented here could encourage the design and development of catalysts with d-sp orbital hybridization.The main research contents of this dissertation are as follows:(1)The d-sp orbital hybridization regulates the properties of d-band on metal surface for highly active HER catalysis.We selected the boron atom with sp orbital and fifteen transition metals to construct a series of transition-metal-boron intermetallics(T_MB)with well-defined crystal structure,and systematically studied the effect of d-sp orbital hybridization on the hydrogen adsorption properties of metal-terminated surface of T_MB.The results show that the d-sp orbital hybridization can weaken the hydrogen adsorption strength on the corresponding transition metal surface.This weakened hydrogen adsorption strength regulates the electrocatalytic hydrogen evolution reaction activity with adsorbed hydrogen as the key intermediate,so that three T_MB intermetallic possess high HER catalytic activity in theory(e.g.,Pd B,Ru B,and Re B).Furthermore,seven T_MBs(e.g.,VB,Nb B,Ta B,Cr B,Mo B,WB,and Ru B)were successfully synthesized by magnesium thermal reduction method at low temperature.Ru B is a highly active Pt-like electrocatalyst for hydrogen evolution reaction.(2)The d-sp orbital hybridization regulates the subordinate/dominant character of highly active catalytic sites on the metal surfaces.It is found that the top site of metal Ru has Pt-like hydrogen adsorption properties,while the adjacent Ru₃-hollow sites have stronger hydrogen adsorption strength,and the highly active Ru top site is a subordinate site.Using six p-block elements X(e.g.,Al,Si,Ga,Ge,In,and Sn)and Ru,we constructed Ru X intermetallic with well-defined crystal structure to regulate the adsorption sites of Ru-based catalysts.Finally,it is found that,compared with other interstitial atoms,after the introduction of Si to form Ru Si intermetallic compound,the d-sp orbital hybridization between Ru and Si can well balance the strain effect,promoting the Ru top sites from subordinate to dominant character and realize Pt-like HER catalytic activity.Furthermore,Ru Si was successfully synthesized by magnesium thermal reduction method at low temperature.Experimental studies further identify intermetallic Ru Si as a highly active,non-Pt material for catalyzing the HER.(3)The d-sp orbital hybridization regulates the nitrogen reduction activity of metal coordinated boron sites.Through high-throughput DFT calculation,478 stable structures were selected from 3660 antiperovskite-type ternary borides(M₃M?B)containing different metal-coordinating isolated boron sites.The effects of different coordination atoms and electronic structures on the dinitrogen adsorption configuration and adsorption energy adsorbed on their surface boron sites were systematically studied.The adsorption and activation of dinitrogen depend on the existence of isolated boron sites on the surface.The adsorption configuration of dinitrogen is closely related to the type of M atoms.M atom and isolated boron sites cooperate to stabilize the nitrogen-containing adsorption intermediate.M?atom can regulate the d-sp orbital hybridization between M and B,so as to control the surface chemisorption of*N intermediate and catalytic activity.Finally,we screened three surfaces with high activity and selectivity for NRR.