The Construction And Performance Of Metal Catalysts For Electrocatalytic Carbon Dioxide Reduction Reaction

The surface structure of metallic catalysts can significantly impact the kinetics of electrochemical CO₂ reduction reaction（CO₂RR）.It is of importance to construct high-performance metallic catalysts and understand the structure-performance relationship for practical application.However,metallic catalysts currently suffer from limited construction strategies,low selectivity for C₂₊products,and poor understanding of the relationship between structure and performance.To address these problems,in this dissertation,a single-site metal catalyst with an enzyme-mimic structure,a binary phase-segregated Ag/Cu alloy and an oxide-derived Cu with low coordinated sites have been constructed.Through XRD,TEM,SEM,FT-IR,electrochemical measurements,in-situ XAFS,in-situ Raman,and theoretical calculations,this work has systematically studied the structure of the constructed catalysts,tested their CO₂RR performances,and revealed the structure-performance relationships.A Co-based single-site polymer catalyst with Co porphyrinic and triazoly groups uniformly distributed in the network skeleton,Co-Por-Triazole,has been constructed by“Click”reaction.Co-Por-Triazole exhibited high performance in the electrochemical reduction of CO₂.The highest CO Faradaic efficiency of 96%was achieved under-0.61 V versus reversible hydrogen electrode（RHE）,and the CO Faradaic efficiency is not less than 80%in a wide range between-0.61 V and-0.81 V versus RHE.DFT calculations and weak interaction analysis revealed that Co-Por-Triazole has an enzyme-mimic microenvironment,in which the triazoly groups located near the Co sites can stabilize the*COOH intermediate through hydrogen bond,thereby reducing the reaction barrier to occur.A new workflow containing electrochemical galvanic replacement,thermal oxidation and in-situ electroreduction is proposed to prepare an oxide-derived Ag/Cu phase-segregated alloy,Ag/Cu＿OD.This study has found that Ag/Cu＿OD can achieve high C₂₊products Faradaic efficiency of 33%and 47%at-1.04 V and-1.24 V versus RHE,respectively.Comparing to oxide-derived Cu（Cu＿OD）with the same pre-oxidation history,Ag/Cu＿OD exhibited a high spillover effect,as3.76-fold C₂₊Faradaic efficiency as that of Cu＿OD at-1.04 V versus RHE.With Ag/Cu＿OD and optimized Pt Ru alloy as cathode and anode,respectively,a two-electrode full cell achieved a large current density～100 m A/cm² at 3.67 V.A nanobelt-like CuO oxide precursor has been constructed through preoxidation of Cu surface with a dilute NaOH aqueous solution.This nanobelt-like CuO oxide precursor turn to oxide-derived Cu,Dilute＿Cu,through in-situ electroreduction during CO₂RR.This study has shown that Dilute＿Cu exhibited high efficiency in electroreduction of CO₂ into propanol（C₃）in netural media and at low overpotential.The best C₃ Faradaci efficiency reached 17.9%at-0.94 V versus RHE.In-situ XAFS study revealed the highly unsaturated coordination state of Dilute＿Cu and its coordination number was only 9.8 at-0.94 V versus RHE.Meanwhile,in-situ Raman study disclose the strong adsorption of C₁ and C₂ intermediates on Dilute＿Cu than oxide-derived Cu samples by pre-oxidation of other condenser NaOH solutions,indicating the key role of the unsaturated coordination state of Cu sites in C₃ generation.