Polyvinyl alcohol-modified gold nanoparticles with record-high activity for electrochemical reduction of CO2 to CO

The surface modification with organic molecules on metal nanoparticles (NPs) has emerged as an effective strategy for tuning the activity and selectivity of CO2 electrochemical reduction. However, the role of capping agents, commonly used for the synthesis of metal NPs, such as polyvinyl alcohol (PVA), is often neglected and rarely investigated from the perspective of surface modification. Herein, we report that the PVA modification as an intriguing approach greatly improves the activity and selectivity of CO2 electrochemical reduction based on surfactant- and polymer-free Au NPs. A record-high geometric current density of 98.6 mA cm(-2) and a Faradaic efficiency of more than 90% for CO production at an overpotential of 660 mV are achieved on the PVA-modified Au NPs, much superior to the naked Au NPs and the current catalysts to date. Tafel analysis indicates that the PVA modification on Au NPs induces a favorable reaction pathway for CO2 reduction, which might be attributed to the stabilized intermediate (*COOH) by hydrogen-bond network from the metal-polymer interface. Furthermore, by taking advantage of the capping agent derived from the synthesis process, Au NPs modified with residual PVA can be prepared conveniently for highly efficient CO2 reduction, which demonstrates a great potential for practical application.