Electrochemical CO2 reduction reaction(CO2RR) to valuable chemicals and fuels is an attractive strategy to balance the anthropogenic carbon circle and store intermittent renewable energy into chemical bonds. The key to advance this technology is to develop stable and efficient electrocatalysts. Recently, pre-oxidation treatments on monometallic catalysts (e.g., Cu, Ag, Au) have been shown to significantly improve CO2RR performance. However, the mechanism underlying the improvements remains a topic of considerable discussions, especially regarding the possibility of oxygen-containing species present at the CO2RR conditions as well as their promotional effect. The instability of the oxygen-containing species introduced by pre-oxidation treatment as well as the challenges in probing the surface species at reaction conditions hinders the efforts in correlating the role of oxygen-containing species with CO2RR performance. In this talk, we present a coelectrolysis strategy of CO2 with O2 to effectively introduce stable oxygen-containing species on catalyst surface during CO2RR. We investigate the surface species on Cu, Ag and Au catalysts at the coelectrolysis conditions and correlate them with CO2RR reactivity. We provide in situ Raman spectral evidence to show that different oxygen-containing species can be formed on Cu and Ag in coelectrolysis with O2, while no oxygen-containing species were found on Au. Consistently, reactivity results show that orders of magnitude enhancement of CO2RR activities can be achieved on Cu and Ag in coelectrolysis with O2, while only modest change was observed on Au. Overall, combining in situ surface-enhanced Raman spectroscopy and reactivity measurements, we demonstrate the important role of oxygen-containing species in promoting CO2RR performance.

Oxygen-containing species enhance CO2 electroreduction via coelectrolysis with O2

ACS Spring 2022

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