Unveiling key impact parameters and mechanistic insights towards activated biochar performance for carbon dioxide reduction

Abstract

Chemically activated biochar is effective in supercapacitors and water splitting, but low conductivity hinders its application as a carbon support in carbon dioxide reduction reaction (CO2RR). Based on the observed CO2RR performance from potassium hydroxide (KOH)-activated biochar, increased microporosity was hypothesized to enhance the performance, leading to selection of potassium carbonate (K2CO3) for activation. K2CO3 activation at 600℃ increased microporosity significantly, yielding a total Faradaic efficiency of 72%, compared to 60% with KOH at 800℃. Further refinement of thermal ramping rate enriched micropore content, directly boosting FEC to 82%. Additionally, K2CO3's lower activation temperature could preserve hydroxyl groups to improve ethylene selectivity. These findings demonstrate that optimizing microporosity and surface chemistry is critical for designing activated biochar-based CO2RR electrocatalysts. Despite lower electrical conductivity of activated biochar, selecting the appropriate activating agents and conditions can make it a viable alternative to carbon black-based electrocatalysts.