Pulsed electrolysis attracts attention as a simple tool for tuning the structure and properties in many electrocatalytic systems. Here, pulsed reaction protocols are used to control the structure and selectivity of copper and nitrogen co-doped carbon (Cu-N-C) catalysts, employed for electrocatalytic CO2 reduction reaction (CO2RR). Specifically, while this catalyst is mostly selective for hydrogen during potentiostatic reduction, as high as 82% Faradaic efficiency for CO2RR products is reached by optimizing the pulse parameters. It is found that the product distribution depends strongly on the values of both the anodic and cathodic potentials, and the pulse parameter ranges for preferential CO, CH4, and C2H4 formation were identified. By performing detailed in situ and operando spectroscopic analysis, it is found that i) pulsing creates a favorable microenvironment for CO2RR by reducing the surface H-coverage on the N-doped carbon support, and ii) the dynamic evolution of the Cu active sites directs the selectivity toward hydrocarbons (CH4, C2H4). The periodic application of increasingly more anodic potentials results in more efficient redispersion of the metallic Cu clusters that are formed under cathodic potential. The C1/C2+ selectivity ratio depends on the fraction of the stabilized Cu single atoms and the size of the Cu particles formed under working conditions.
Hursán et al. (Wed,) studied this question.