A High Power Density Zn‐Nitrate Electrochemical Cell Based on Theoretically Screened Catalysts

Abstract Designing artificial nitrogen fixing devices with functions of light energy adsorption and driven nitrogen species upgrade and oxygen evolution is highly attractive. However, advanced catalytic materials for key NO₃^‐‐to‐NH₄⁺ and OH^‐‐to‐O₂ reactions are rather rare. Herein, first principle calculations are performed to pre‐screen target catalysts and then the effective catalyst in the experiment is successfully prepared, with which, a high power density Zn‐nitrate electrochemical cell is demonstrated. The cathode catalyst can promote both reductive NO₃^‐‐to‐NH₄⁺ and oxidative OH^‐‐to‐O₂ reactions in low‐overpotential pathways, contributing to the total battery reaction: NO₃^‐ + 3H₂O → NH₄⁺ + 2OH^‐ + 2O₂. The resulting electrochemical cell shows over 90% NO₃^‐‐to‐NH₄⁺ selectivity, a high power density over 25 mW cm^‐2, and stable 35 h cycling at 12.5 mA cm^‐2. Moreover, this Zn‐nitrate electrochemical cell can work driven by the photovoltaic cell with the solar‐to‐NH₃ efficiency up to 19.5%. This study demonstrates a theoretically screened catalyst realizing a photovoltaic driven high‐rate Zn‐nitrate electrochemical cell system, which mimics soybean system upgrading N species and producing oxygen.