Speakers
Description
Electrochemical CO$_2$ reduction reaction (CO$_2$RR) over Cu based catalysts is a promising process to produce useful chemicals and fuels, but suffers from low energy efficiency and product selectivity. Among various strategy to enhance the product selectivity of CO$_2$RR, applying periodic oxidative potentials (i.e., the pulsed electrolysis) during the CO$_2$RR have been shown to be an efficient way to steer the selectivity toward certain desired products.$^1$
Herein, we have taken advantage of a pulsed CO$_2$RR approach to tune the product selectivity of 1) shape-controlled Cu$_2$O nanocube (NC) and 2) Cu-nitrogen doped carbon catalysts. For the Cu$_2$O NC catalysts, we compared the CO$_2$RR selectivity subjected to either potentiostatic or pulsed electrolysis conditions at industrially relevant current densities in a gas-fed flow cell. We found that the product selectivity can be effectively controlled by tuning the value of the applied anodic potential (E$_{an}$), allowing us to switch from C$_2$ (C$_2$H$_4$ and C$_2$H$_5$OH) to C$_1$ (CH$_4$) product formation. For Cu-nitrogen doped carbon catalysts, we found drastically suppressed H$_2$ evolution and increased selectivity for methane and C$_{2+}$ products under pulsed conditions, compared to the potentiostatic CO$_2$RR. For both catalytic systems, by means of ex situ, in situ and operando characterization methods, we gained insights into the morphology, chemical state and local environment of Cu based catalytic systems during the pulsed CO$_2$RR. This allowed us to correlate CO$_2$RR selectivity changes with changes in chemical and physical Cu based catalyst properties, thus gaining a mechanistic understanding of how the Cu based catalyst adapt its properties.
References
1. R. M. Arán-Ais, F. Scholten, S. Kunze, R. Rizo, B. Roldan Cuenya, Nat. Energy 5, 317 (2020).
