Study On The Design Of Metal-Based Catalytic Materials And Their Performance In Electrocatalytic CO₂ Reduction

The massive use of fossil fuels since the industrial revolution has led to excessive carbon dioxide（CO₂）emissions,causing serious environmental pollution.For this reason,some countries have committed to a zero-emission（zero-carbon）economy to mitigate environmental pollution and climate change.Among the many methods of CO₂ resource utilization such as thermocatalysis,electrocatalysis,and photocatalysis,electrocatalytic CO₂ reduction（ECR）is a feasible way to achieve zero carbon emission.On the one hand,ECR can be combined with renewable energy power,making it more economical and environmentally friendly;on the other hand,ECR can convert CO₂ into valuable chemicals such as ethylene（C₂H₄）and formic acid（HCOOH）under mild conditions.However,ECR catalysts still face problems such as low selectivity,instability,and low yield.To solve these problems,researchers are committed to develop catalysts with high Faraday efficiency（FE）and low overpotential.In this thesis,mainly from the economic value of C₂H₄,CuBi-based catalysts were designed to achieve the conversion of C₁ to C₂ products.The specific research contents are as follows:（1）Atomically dispersed Bi-doped defective copper oxide（CuO） catalysts（Bi-CuO（V_o）＿0.5%）were prepared by a simple hydrothermal method.Bi single atom and oxygen vacancy jointly promoted the efficient production of C₂H₄ on Bi-CuO（V_o）＿0.5%catalysts.In contrast to CuO,XRD,Raman,and electron microscopy tests jointly demonstrate the generation of Bi single atom doped CuO,and XPS demonstrates the increase of oxygen vacancies after Bi doping.Through electrochemical tests,maximum FE of C₂H₄ produced by Bi-CuO（V_o）＿0.5%is 48.2±2.1%,at a low potential of-1.05 V vs.RHE in an H-type cell,which is about two times that of pure CuO,with a maximum C₂H₄partial current density of-9.1 m A cm^-2,which is better than the performance of most commercial catalysts（such as commercial CuO,Cu,Cu₂O,etc.）.The C₂H₄FE of Bi-CuO（V_o）＿0.5%is up to 60.2±0.4%with 1 M KOH electrolyte in a flow cell.Density functional theory（DFT）calculation shows that the Bi single atom and oxygen vacancy can jointly lower the polymerization energy barrier of the*CO intermediate and thus improve the performance of C-C coupling to produce C₂H₄.（2）Cu₉₇Bi₃ aerogel was prepared by one-step reduction using high concentration sodium borohydride（Na BH₄）solution as reducing agent.The characterization by XRD,XPS and UV-Vis spectra proved the generation of Cu₉₇Bi₃ alloy and SEM confirmed the aerogel structure of Cu₉₇Bi₃.By regulating the ratio of the precursor of metal Cuand Bi,the main products can be tuned from C₁（HCOOH）to C₂（C₂H₄）.The FE of C₂H₄ over Cu₉₇Bi₃was maintained after electrolysis for up to 12.0 h.The CO electroreduction experiments prove that Cu₉₇Bi₃ is more favorable for CO adsorption than Cu₁₀₀.Compared with Cu₁₀₀,the enhanced activity of Cu₉₇Bi₃ aerogel can be attributed to two aspects:firstly,Cu₉₇Bi₃ aerogel with spongy three-dimensional structure has large specific surface area and abundant pore channels,which is conducive to efficient mass transfer.And secondly,in terms of synergistic effects,the bimetallic Cu-Bi alloy can greatly improve the ECR activity of the catalyst,providing an effective method for efficient production of C₂ products from non-noble metal CuBi materials.