Halogen/Nitrogen Codoped Carbon Encapsulated Ni Nanoparticles for Efficient CO2 Electroreduction and High-Performance Zn-CO2 Batteries

Electroreduction of CO₂ (ECR) to CO or syngas is an effective approach to alleviating greenhouse gas emissions. Herein, nickel nanoparticles coated with halogen/nitrogen codoped carbon were prepared (X-Ni/NC-a). Cl-Ni/NC-a can obtain three important syngas compositions (CO:H₂) under different voltages, such as 0.97, 0.51, and 0.32, which are the ratios for hydroformylation, methanol, and ethanol synthesis, respectively. For Br-Ni/NC-a, the CO Faraday efficiency (FE_co) can exceed 96%, with a CO partial current density (j_co) of 48 mA cm^-2. Additionally, Br-Ni/NC-a is used in a Zn-CO₂ battery (ZCB); the power density can reach 2.6 mW cm^-2, and the charge-discharge stability can reach 110 h. DFT calculations revealed that the strong interaction between nickel nanoparticles and halogen/nitrogen codoped carbon regulates the electronic structure of the catalyst, affecting the adsorption/desorption of intermediates. This study provides a feasible scheme for halogen doping to modulate the selectivity of ECR and the potential application of catalysts in ZCB.