Modulating Cu/Cu_xO Amount in Cu/Cu_xO-SnO_x 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/Cu_xO-SnO_x supported on nitrogen-doped carbon cuboids is studied as an efficient electrocatalyst system for CO₂ reduction. Fine-tuning of the Cu/Cu_xO 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/Cu_xO and SnO_x can suppress the HER and simultaneously reduce the overpotential.