Structure and Phase Evolution of CuS<i><sub>x</sub></i> Electrocatalysts During CO<sub>2</sub> Electroreduction Reaction
Qian Zhang, Qingye Ren, Li Zhang, Lifeng Zhang, Langli Luo
Abstract
Electrochemical conversion of CO 2 to value-added chemicals or fuels is an efficient route to achieving economic and environmentally sustainable green carbon cycles. Copper sulfide (CuS x ) is an effective catalyst for the electrochemical reduction of CO 2 to formic acid (HCOOH) with a high Faraday efficiency at a low voltage, where sulfur plays a key role in steering the Cu from multicarbon products to highly selective HCOOH production. The active structure and phase of CuS x during the CO 2 reduction reaction determine its catalytic activity and long-term stability, which remain largely elusive. We prepared a model CuS x hollow nanocube electrocatalyst to elucidate the microstructure changes down to the atomic scale and also track the phase changes of CuS x during the reaction. We revealed that the active site for HCOOH production is the Cu 2 S species, which forms immediately upon the reaction and covers the surface of CuS x . Additionally, the consumption of this surface species holds the key to continuous HCOOH production.