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

Partially positive-charged copper (Cu δ+ ) is known to boost the formation of highly valued multicarbon C 2+ products during the electrochemical CO 2 reduction reaction (CO 2 RR). In this work, we doped boron in copper oxide (B–CuO) to create Cu δ+ sites and studied two important aspects regarding the CO 2 RR: (1) the direct observation of the CO reaction intermediate on the Cu δ+ surface and (2) the role of Cu δ+ in enhancing C 2+ 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 CO 2 RR. We observed that multiple CO adsorption sites and strong adsorption of the CO intermediate on the Cu δ+ surface promote the C–C coupling reaction in B–CuO. As a result, we achieved a C 2+ 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.