Steering hydrogen evolution in CO2 electroreduction through tailoring various co-catalysts

Abstract

Electrochemical CO2 reduction reaction (CO2RR) is a sustainable approach to producing carbon-neutral fuels when combined with renewable energies. Besides the emphatic consideration of developing efficient catalysts, a suitable conductive carbon agent served as co-catalyst with a low activity toward the competitive hydrogen evolution reaction (HER), is also highly needed. However, there have been limited studies focused on the investigation of co-catalyst during CO2RR, especially on their HER behavior. We herein explored the HER of various co-catalyst, i.e., acetylene black (AB), carbon black (CB) and graphite flake (GF) as well as carbon nanotube (CNT), and their composites with sub-25 nm Ag nanowires (NWs) as catalysts. GF and CB exhibit a higher activity toward CO2RR and HER, respectively. In contrast, CB/Ag NWs achieve the highest Faraday efficiency and partial current density for CO2RR, whereas CNT/Ag NWs prefer HER. The differences in HER suggest a critical influence of co-catalyst and this study points to a better guidance on the selection of co-catalyst for CO2RR. Keywords: Carbon dioxide reduction reaction, Hydrogen evolution reaction, Carbon support material, Ag nanowires