Insight into the effect of surface coverage of carbon support on selective CO2 electroreduction to C2H4 over copper-based catalyst

The electrocatalytic CO2 reduction is a promising strategy for CO2 resource utilization, and copper-based catalysts are well-known to be positive for converting CO2 to ethylene. However, the ethylene selectivity and catalyst persistence still need to be improved. Herein, a series of Metal- and nitrogen-doped carbon composite electrocatalysts with different ingredient ratios were constructed by pyrolysis of Cu(NO3)2 and polyvinyl pyrrolidone mixed precursor for CO2 reduction. Among these composite catalysts, the excessive Cu content caused an increase in the size of Cu nanoparticles and the surface coverage of carbon support, resulting in a highly competitive H2 evolution and a quite low CO2RR activity. Among the series of the catalysts with different ingredient ratios, Cu-10/NC with suitable catalyst formulation exhibited smaller Cu nanoparticle size and lower surface coverage, resulting in higher CO2 activity and conversion. Besides, there were more Cu+ existed in Cu-10/NC, which could be reduced to low coordination Cu under the electrochemical reduction process, resulting in enhanced *CO binding energy and stabilized *CO intermediates. Combining the high contents of pyrrolic-N and Cu-N doped in Cu-10/NC, which could lower the CC dimerization activations barriers and facilitated CC coupling reactions on Cu surface, all of these features contributed that Cu-10/NC was the optimal catalyst for CO2RR to ethylene. The FEC2H4 of Cu-10/NC reached 37 % at − 1.2 V (vs RHE) and the electrocatalytic performance remained stable over 7 h. These findings provide new references to develop high-efficiency CO2 reduction electrocatalysts.