Modulating Cu/CuxO Amount in Cu/CuxO–SnOx Nitrogen-Doped Porous Carbon Cuboids toward Low Overpotential CO2 Conversion to Formate

Modulating the electrocatalyst materials with different metal/metal oxides is a beneficial way to enhance the electrochemical reduction of CO2 into valuable chemical feedstock. Herein, a multicomponent system composed of Cu/CuxO-SnOx supported on nitrogen-doped carbon cuboids is studied as an efficient electrocatalyst system for CO2 reduction. Fine-tuning of the Cu/CuxO amount significantly altered the catalyst performance with regard to selectivity and overpotential. A higher overpotential was needed to primarily convert CO2 to formate in the presence of an appreciable amount of Cu (17 at. %), whereas the selectivity of the multicomponent system toward formate was enhanced (with a maximum FE of 69% at −1.1 V vs RHE) when the system had only a minute amount of Cu (0.86 at. %). Interestingly, optimizing the Cu amount resulted in generating formate with a FE of (39%) at low overpotential (−0.5 V vs RHE), which is a rarely reported performance for similar systems. Controlling the metal/metal oxide ratio altered the electron density of each component and changed the kinetics of the CO2 reduction pathways. Notably, the presence of Cu/CuxO and SnOx can suppress the HER and simultaneously reduce the overpotential. The developed system yields efficient electrocatalyst materials with a distinct heterogeneous structure that has rarely been investigated for the electrochemical conversion of CO2.