Biomass-Derived N-Doped Carbon for Efficient Electrocatalytic CO₂ Reduction to CO and Zn-CO₂ Batteries

Conversion of CO₂ into valuable chemicals via electrochemical CO₂ reduction reaction (CO₂RR) is a promising technology to alleviate the energy crisis and the greenhouse effect. Herein, low-cost wood biomass was applied as the carbon source to prepare nitrogen (N)-doped carbon electrocatalysts for the conversion of CO₂ to CO and further as the cathode material for Zn-CO₂ batteries. By virtue of N-doping and assistance of FeCl₃, a cedar biomass-derived three-dimensional (3D) N-doped graphitized carbon with a high N-doping content (5.38%), an ultrahigh specific surface area (1673.6 m² g^-1), rich nanopores, and sufficient active N sites was successfully obtained, which exhibited super CO₂RR activity with a high faradaic efficiency of 91% at a low applied potential of 0.56 V (vs RHE) and a long-term stability for at least 20 h. Furthermore, a Zn-CO₂ battery with it as the cathode material delivered a stable open circuit voltage of 0.79 V, a peak power density of 0.51 mW cm^-2 at 2.14 mA cm^-2, and a maximum faradaic efficiency to CO of 80.4% at 2.56 mA cm^-2, indicating that it could be applied in a practical process by using CO₂ to generate power with the production of CO. Density functional theory calculations revealed that pyridinic N could more effectively decrease the free energy barriers for CO₂RR and boost the reaction. This work not only revealed a facile approach to convert waste biomass into N-doped-graphitization carbon as valuable CO₂RR electrocatalysts but also provided a new strategy to achieve "carbon solving carbon's problem".