Electroreduction of CO2 on Single-Site Copper-Nitrogen-Doped Carbon Material: Selective Formation of Ethanol and Reversible Restructuration of the Metal Sites

Abstract

It is generally believed that CO₂ electroreduction to multi-carbon products such as ethanol or ethylene may be catalyzed with significant yield only on metallic copper surfaces, implying large ensembles of copper atoms. Here, we report on an inexpensive Cu-N-C material prepared via a simple pyrolytic route that exclusively feature single copper atoms with a CuN₄ coordination environment, atomically dispersed in a nitrogen-doped conductive carbon matrix. This material achieves aqueous CO₂ electroreduction to ethanol at a Faradaic yield of 55 % under optimized conditions (electrolyte: 0.1 m CsHCO₃ , potential: -1.2 V vs. RHE and gas-phase recycling set up), as well as CO electroreduction to C₂ -products (ethanol and ethylene) with a Faradaic yield of 80 %. During electrolysis the isolated sites transiently convert into metallic copper nanoparticles, as shown by operando XAS analysis, which are likely to be the catalytically active species. Remarkably, this process is reversible and the initial material is recovered intact after electrolysis.

Keywords: CO2 electroreduction; copper; ethanol; operando analysis; single-site catalyst.