Gas-phase electrocatalytic conversion of CO2 to chemicals on sputtered Cu and Cu–C catalysts electrodes

A novel gas-phase electrocatalytic cell containing a low-temperature proton exchange membrane (PEM) was developed to electrochemically convert CO2 into organic compounds. Two different Cu-based cathode catalysts (Cu and Cu–C) were prepared by physical vapor deposition method (sputtering) and subsequently employed for the gas-phase electroreduction of CO2 at different temperatures (70–90 °C). The prepared electrodes Cu and Cu–C were characterized by X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS) and scanning electron microscopy (SEM). As revealed, Cu is partially oxidized on the surface of the samples and the Cu and Cu–C cathodic catalysts were comprised of a porous, continuous, and homogeneous film with nanocrystalline Cu with a grain size of 16 and 8 nm, respectively. The influence of the applied current and temperature on the electro-catalytic activity and selectivity of these materials was investigated. Among the two investigated electrodes, the pure Cu catalyst film showed the highest CO2 specific electrocatalytic reduction rates and higher selectivity to methanol formation compared to the Cu–C electrode, which was attributed to the higher particle size of the former and lower CuO/Cu ratio. The obtained results show potential interest for the possible use of electrical renewable energy for the transformation of CO2 into valuable products using low metal loading Cu based electrodes (0.5 mg Cu cm−2) prepared by sputtering.