Bi1‐CuCo2O4 Hollow Carbon Nanofibers Boosts NH3 Production from Electrocatalytic Nitrate Reduction

Abstract Ammonia, as a high‐energy‐density carrier for hydrogen storage, is in great demand worldwide. Electrocatalytic nitrate reduction reaction (NO 3 RR) provides a green NH 3 production process. However, the complex reaction pathways for NO 3 RR to NH 3 and the difficulty in controlling intermediate products limit the reduction process. Herein, by incorporating atomic‐level bismuth (Bi) into CuCo 2 O 4 hollow carbon nanofibers, the catalytic activity of the electrocatalyst for NO 3 RR is enhanced. The maximum Faradaic efficiency of Bi 1 ‐CuCo 2 O 4 is 95.53%, with an NH 3 yield of 448.74 µmol h −1 cm −2 at −0.8 V versus RHE. Density Functional Theory calculations show that the presence of Bi lowers the reaction barrier for the hydrogenation step from *NO 2 to *NO 2 H, while promoting mass transfer on the release of *NH 3 and the reactivation of surface‐active sites. Differential charge density calculations also show that after Bi doping, the charge supplied by the catalyst to NO 3 − increases from 0.62 to 0.72 e ‐ , thus reasoned for enhanced NO 3 RR activity. The established nitrate‐Zn battery shows an energy density of 2.81 mW cm −2 , thus implying the potential application.