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

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. •Various co-catalysts, coupled with Ag NWs, were examined for CO2RR.•HER of co-catalysts, and their influences on the selectivity were discussed.•GF and CB exhibit higher activities toward CO2RR and HER, respectively.•CB/Ag NWs is more active for CO2RR, whereas CNT/Ag NWs prefer HER.•Steering HER in CO2RR through tailoring various co-catalysts is proposed.