Monolithic Cl-Modified Nanoporous Ag Nanowires for Electrochemical CO2 Reduction to CO

Abstract

Nanoporous catalysts with large surface areas are promising electrocatalysts to reduce carbon dioxide (CO2). However, previous methods of producing nanoporous catalysts require a high temperature (>500 °C) or a long processing time (∼12 h). Herein, we develop a facile method to produce monolithic nanoporous Ag nanowires (NWs) within a few minutes. The Cl2 plasma treatment on a Ag-coated plastic film induces the rapid growth of vertically aligned AgCl NWs due to the highly reactive Cl radicals and strain-relaxation-driven growth of NWs. Then, AgCl NWs are electrochemically reduced to produce nanoporous Ag NWs with a high electrochemical surface area. Moreover, the residual Cl– anions on the surface of the nanoporous Ag NWs increase CO2 reduction activity. Consequently, the Ag NWs have a 90 times higher electrochemical surface area but less than 0.06 times as much charge-transfer resistance as the Ag film. As a result, the Ag NWs achieve a high selectivity of CO (FECO = 98.7%) and high CO partial current density of 3.16 mA/cm2 at −0.8 VRHE, which is 20 times higher than that of Ag foil (0.16 mA/cm2). Moreover, the Ag NWs had a good long-term stability even after 60 h of CO2 reduction.