Enhanced Electrochemical CO(2) Reduction to Formate on Poly(4-vinylpyridine)-Modified Copper and Gold Electrodes

[Image: see text] Developing active and selective catalysts that convert CO(2) into valuable products remains a critical challenge for further application of the electrochemical CO(2) reduction reaction (CO(2)RR). Catalytic tuning with organic additives/films has emerged as a promising strategy to tune CO(2)RR activity and selectivity. Herein, we report a facile method to significantly change CO(2)RR selectivity and activity of copper and gold electrodes. We found improved selectivity toward HCOOH at low overpotentials on both polycrystalline Cu and Au electrodes after chemical modification with a poly(4-vinylpyridine) (P4VP) layer. In situ attenuated total reflection surface-enhanced infrared reflection-adsorption spectroscopy and contact angle measurements indicate that the hydrophobic nature of the P4VP layer limits mass transport of HCO(3)(–) and H(2)O, whereas it has little influence on CO(2) mass transport. Moreover, the early onset of HCOOH formation and the enhanced formation of HCOOH over CO suggest that P4VP modification promotes a surface hydride mechanism for HCOOH formation on both electrodes.