Biomass-based carbon aerogels prepared by ZnCl2-assisted pyrolysis of cellulosic aerogels for selective electrocatalytic CO2 reduction

Carbon aerogel is a promising electrodes material for electrocatalytic CO2 reduction reaction (CO2RR) due to its hierarchical porous structure and large specific area. However, using renewable and wide-sourced precursors to prepare green catalysts with comparable commercial CO2RR performance is still a challenge. Herein, a green ZnCl2-modified biomass-based carbon aerogel was fabricated. The cellulose and ZnCl2 were used as a biomass model compound and activator, respectively. The results showed that the morphology of carbon aerogels can be controllable by thermal etching between ZnCl2 and aerogel under different pyrolysis temperature. At low pyrolysis temperatures (below 750 °C), the carbon aerogel exhibited three-dimensions hierarchical pore structure with abundant ZnO, which was conducive to the conversion of CO2 to CO. As the temperature raised, ZnO rapidly decreased and eventually disappeared. At 950 °C, the unique flocculent structure with rich defects was formed, and the main conversion products changed from CO (a maximum faradic efficiency of 78%) to syngas (CO:H2 =1:1).