Study Of Copper-based Electrocatalyst For Electrochemical Carbon Dioxide Reduction Reaction

With the excessive consumption of fossil fuels and emissions of CO₂,it has led to a series of environmental crises,such as global warming and rising sea levels.Therefore,the conversion of CO₂ into various carbon-containing chemicals can help alleviate the environmental crisis caused by CO₂ overdischarge.Among diversified technologies for CO₂ conversion,electrochemical CO₂ reduction reaction（CO₂RR）is emerging as a highly promising technology.A variety of metal-based electrocatalysts have been developed for CO₂RR.Among them,Cu-based electrocatalysts are unique for the generation of multi-carbon products.In particular,Cu metal-organic frameworks（MOFs）is a kind of interesting electrocatalyst precursors with abundant pores,high specific surface area,and tunable structure and composition.Therefore,Cu-based electrocatalysts derived from Cu MOFs precursors represents an important strategy for the design and creation of advanced CO₂RR electrocatalysts.Herein,different Cu-based MOFs precursors were synthesized by two modification strategies,and Cu-based electrocatalysts were obtained by further pyrolysis.The main research works and achievements are as follows:（1）In the synthesis process of HKUST-1,benzimidazole was used as a nitrogen source to partially replace trimesic acid and coordinate with copper ion to synthesize the precursor with yolk-shell structure.Further,the nitrogen-modified Cu-based electrocatalyst was obtained after pyrolysis.The precursors and electrocatalysts were characterized,and the amount of introduced benzimidazole,pyrolysis temperature,and working electrode loading were investigated and optimized.The electrocatalyst demonstrated an ethylene Faradic efficiency（FE）of 25.8%and a partial ethylene current density of 23.7 m A/cm²,and remained stable during electrolysis for10 h.In addition,the ethylene selectivity and stability of the electrocatalyst were significantly better than those of the electrocatalyst without nitrogen modification.Combined with electrochemical tests and X-ray photoelectron spectroscopy（XPS）,the modification of nitrogen helped to stabilize Cu（I）species and promote CO₂ activation,while supressing the reduction of Cu（I）species during electrolysis.Moreover,the electrocatalyst also showed good performance in a flow cell.（2）During synthesis of HKUST-1,copper and cerium ions were added to coordinate with trimesic acid at the same time to synthesize the composite precursor of copper and cerium bimetal MOFs.After pyrolysis,the Cu-based electrocatalyst modified by Ce O₂ was obtained.The precursors and electrocatalysts were characterized to verify the stable synthesis of bimetallic MOFs composite precursors,and the metal ratio of copper to cerium and pyrolysis temperature were optimized.The prepared electrocatalyst showed an ethylene FE of 30.5%and a partial ethylene current density of 27.5 m A/cm².The performance of the electrocatalyst modified by Ce O₂ was significantly improved.Furthermore,the performance of electrocatalyst could maintain stable during electrolysis for 8 h.