Construction Of Metal Single Atom Based Catalysts For Electrocatalytic Carbon Dioxide Reduction

To achieve the goals of carbon peak in 2030 and carbon neutrality in 2060,the capture and conversion of carbon dioxide has become an urgent issue.Electrocatalytic carbon dioxide reduction reaction(CO2RR)is a promising strategy to solve excessive CO2 emission and produce high value-added chemicals and fuels,thus achieving green and sustainable development.However,due to its slow dynamic process and competitive hydrogen evolution reaction,the rational design of highly active and selective catalysts is highly crucial.Single atom based catalysts with well-defined structure,high atomic utilization and excellent catalytic activity have attracted extensive research interest.In this thesis,within the framework of single atom catalysts,diatomic bridging structure,single atoms coupled nanoparticles,coordination of atomic sites and single atoms alloy were constructed to implove the catalytic performance.Combined the in situ characterization techniques and theoretical calculations,the detailed examination on the relationship between structure and electrocatlytic performance was revealed,to obtain fundamental priciples for designing stable and efficient non-precious metallic single atom-based catalysts.The main results are summarized below:(1)Electrocatalysts with nickel bridging structure dispersed in nitrogen-doped carbon(CNC)fibers were prepared by a simple electrospun-pyrolysis strategy.The experimental results and theoretical calculations revealed that the unique chemical structure of binuclear nickel bridging with nitrogen and carbon atoms(namely Ni2-N4-C2)tunes the electronic nature of d-states for the optimal adsorption of carbon dioxide and intermediates,thus inducing the substantial enhancement of CO2 reduction via the thermodynamically more favorable pathway.A high CO selectivity of 97.8%is achieved in a flow cell under-0.5 V vs RHE,and the assembled Zn-CO2 electrochemical cell with the Ni2-N4-C2 electrocatalyst demonstrates a high peak power density of 2.43 mW cm-2,achieving excellent energy conversion potential.(2)A self-feeding deposition strategy was demonstrated to form the(Ni@C/NiNCNT electrocatalyst by dispersing single nickel atoms on the wall of nitrogen-doped carbon nanotubes,thus inhibiting the thermal aggregation of nickel nanoparticles.In situ characterization,theoretical calculation and electrochemical results show that the heterogeneous nucleo-/electro-philic interface formed by the effective coupling between the single atom sites and nickel particles facilitates the targeted adsorption and activation of CO2 and benzylamine molecules,respectively thereby reducing the reaction barrier and improving the electrocatalytic performance.The Faraday efficiencies of CO and benzonitrile are up to 99.3 and 98%,respectively,achieving the efficient production of high value-added products.(3)An alien atomic bridge structure electrocatalyst with ensemble surface of atomic bismuth modulated indium is elaborately designed via electrochemical reduction and in-situ anchoring strategy.As revealed by in situ structure analysis and theoretical calculation,the regulation of alien bismuth atoms on indium surface enables the charge density gradient to significantly promote the adsorption of*OCHO intermediate by the σ bonding and π*backdonation.This catalyst exhibited a high formate Faraday efficiency(FE)of 95.1%and an extremely long(9 days)electrolytic stability.By coupling 5-hydroxymethylfurfural oxidation(HMF)with CO2RR,the solar-driven full cell demonstrates high formate and 2,5furanocarboxylic acid(FDCA)yields,highlighting the impressive solar-to-fuel conversion selectivity.(4)The V single atoms are in situ confined on the Bi metallene support with rich grain boundaries by the electrochemical reduction method.The analysis of electron status by theoretical calculation shows that the single V atom coordinated Bi active centers with electrondeficient nature enables efficient CO2 activation via the α-donation of O-to-Bi to form*OCHO intermediate,thus reducing the energy barrier for formate production.The FE for C1 profucts nearly 100%in a wide potential range from-0.6 to-1.4 V was achieved and the coupled solar driven CO2-HMF electrochemical cell exhibited a high FDCA yields of 90.5%,showing excellent energy conversion efficiency.