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

Ammonia, as a high-energy-density carrier for hydrogen storage, is in great demand worldwide. Electrocatalytic nitrate reduction reaction (NO3RR) provides a green NH3 production process. However, the complex reaction pathways for NO3RR to NH3 and the difficulty in controlling intermediate products limit the reduction process. Herein, by incorporating atomic-level bismuth (Bi) into CuCo2O4 hollow carbon nanofibers, the catalytic activity of the electrocatalyst for NO3RR is enhanced. The maximum Faradaic efficiency of Bi-1-CuCo2O4 is 95.53%, with an NH3 yield of 448.74 mu mol 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 *NO2 to *NO2H, while promoting mass transfer on the release of *NH3 and the reactivation of surface-active sites. Differential charge density calculations also show that after Bi doping, the charge supplied by the catalyst to NO3- increases from 0.62 to 0.72 e(-), thus reasoned for enhanced NO3RR activity. The established nitrate-Zn battery shows an energy density of 2.81 mW cm(-2), thus implying the potential application.