Electrochemical reduction of CO2 to synthesis gas with controlled CO/H2 ratios

Abstract

The electrochemical carbon dioxide reduction reaction (CO₂RR) to simultaneously produce carbon monoxide (CO) and hydrogen (H₂) has been achieved on carbon supported palladium (Pd/C) nanoparticles in an aqueous electrolyte. The synthesis gas product has a CO to H₂ ratio between 0.5 and 1, which is in the desirable range for thermochemical synthesis of methanol and Fischer–Tropsch reactions using existing industrial processes. In situ X-ray absorption spectroscopy in both near-edge (XANES) and extended regions (EXAFS) and in situ X-ray diffraction show that Pd has transformed into β-phase palladium hydride (β-PdH) during the CO₂RR. Density functional theory (DFT) calculations demonstrate that the binding energies of both adsorbed CO and H are significantly weakened on PdH than on Pd surfaces, and that these energies are potential descriptors to facilitate the search for more efficient electrocatalysts for syngas production through the CO₂RR.