Thin Film Cu1-xNx Catalysts for efficient CO2 Reduction: A Scalable Magnetron Sputtering Approach

Abstract

Thin – film – based catalysts, fabricated through physical vapor deposition, have attracted significant interest as promising materials for electrochemical CO2 reduction. In this context, metallic Cu films function as active catalyst layers for the reduction to ethylene and ethanol. However, these films still experience high overpotentials, resulting in low energy efficiencies. In this study, we have fabricated Cu1-xNx films to overcome this issue by incorporating nitrogen into the sputtering process, leading to the formation of a film with the anti – ReO3 crystal structure of Cu3N, containing Cu either as interstitial vacancies or domains. Under optimal sputtering conditions of rN2 = 0.50, sputter rate = 4 Å s-1, and pressure = 6 µbar, EDX analysis reveals a sub-stoichiometric thin – film composed of Cu0.84N0.16. In the electrochemical CO2 reduction, this film resulted in an increase in energy efficiency from 15.8% to 20% for ethylene compared to pure Cu films, which was attributed to a decrease in the measured potential by ± 500 mV, due to the addition of nitrogen in the structure. This key finding suggests that for future applications, Cu1-xNx layers should be employed instead of metallic Cu to reduce the required energy demands while maintaining selectivity.

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