Porous biochar with a tubular structure for photothermal CO2 cycloaddition: One-step doping versus two-step doping

Solar-powered carbon dioxide (CO2) conversion over biomass derived carbon (BC) has shown great promise for alleviating global warming and producing useful chemicals. However, their lack of active sites, rapid recombination of photogenerated electron-hole pairs, and low CO2 uptake abilities pose significant challenges for photo-induced catalysis. Here, we report the fine-tuning of active sites of BC via one-step and two-step calcination of corn stalk with a tubular structure. Strikingly, compared with samples prepared by two-step doping strategies, NB-BC synthesized via a one-step doping process harbors much enhanced activity under relatively mild conditions (Xe lamp, 400 mW/cm2, 1 bar CO2) with a considerable cyclic carbonate yield of 99%. The high catalytic performance is attributed to the alteration of pore structure, electronic structure, and active sites due to N, B doping. Moreover, this biochar displays excellent recyclability and retains its applicability under simulated flue gas conditions. Various characterizations and control experiments reveal the combination of thermal catalysis and photocatalysis over this N, B co-doped BC catalyst. Our work provides some insights into the effective applications of biochar in the field of CO2 catalytic conversion.