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

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.