Operando Spectroscopic Investigation of a Boron-Doped CuO Catalyst and Its Role in Selective Electrochemical C–C Coupling

Partially positive-charged copper (Cuδ+) is known to boost the formation of highly valued multicarbon C2+ products during the electrochemical CO2 reduction reaction (CO2RR). In this work, we doped boron in copper oxide (B–CuO) to create Cuδ+ sites and studied two important aspects regarding the CO2RR: (1) the direct observation of the CO reaction intermediate on the Cuδ+ surface and (2) the role of Cuδ+ in enhancing C2+ selectivity. Operando attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) showed that distinct CO intermediates were present on CuO and B–CuO surfaces during the CO2RR. We observed that multiple CO adsorption sites and strong adsorption of the CO intermediate on the Cuδ+ surface promote the C–C coupling reaction in B–CuO. As a result, we achieved a C2+ Faradaic efficiency of 62.1% at −0.62 V versus reversible hydrogen electrode on B–CuO. In contrast, only 48% was achieved at −0.65 V on the CuO catalyst.