Electrochemical Carbon Dioxide Reduction on Femtosecond Laser-Processed Copper Electrodes: Effect on the Liquid Products by Structuring and Doping

A femtosecond laser process is presented increasing the surface area of copper electrocatalysts for an electrochemical CO2 reduction reaction (CO2RR). The laser treatment allows us to tune the surface morphology and the chemical composition of the copper electrocatalysts. This tunability is used to correlate the role of the surface area and catalyst dopants with the selectivity of the CO2RR. The liquid products of the CO2RR are monitored through ex situ nuclear magnetic resonance spectroscopy. The products' distribution shows that the electrode surface area plays a key role in the electrochemical conversion of CO2 into multicarbon liquid products. We show that sulfur dopants boost the production of formate. Remarkably, by co-doping sulfur and fluoride, we show that the chalcogenide dopant counteracts the known boosting effect of fluoride to convert CO2 into multicarbon products. Oxygen doping in the range of 2-19 atom % does not significantly affect the distribution of liquid products from CO2 electroreduction. In a broad perspective, this work highlights the potential of the femtosecond laser process to fine-tune surfaces to produce photo- and electrocatalyst materials.