Manipulating Local Electron Density of Fe Nanoclusters with Cerium Incorporation to Optimize Adsorption Behavior of N-Related Intermediates for Electrochemical Ammonia Synthesis from Nitrite

Cluster-scale metal ensembles feature high atomic utilization characteristics, but their activity and selectivity toward the electrocatalytic nitrite reduction reaction (NO₂RR) remain suboptimal. As conventional holders of 4f orbitals, rare earth elements, especially cerium, are drawing wide attention as efficient promoters for transition-metal-based materials. Herein, Ce is incorporated into the Fe nanocluster to manipulate its local electron density for efficient NO₂RR. The presence of Ce with a unique 4f subshell electron configuration effectively withdraws electrons from the outmost 3d orbitals of adjacent Fe, an electronic modulation likely attributable to the pronounced lanthanide contraction effect. Consequently, the energy level of Fe 3d orbital electrons is shifted closer to the Fermi level, thereby promoting stronger adsorption and stabilization of N-related intermediates, as demonstrated by a series of operando characterizations. As expected, a maximum NH₃ yield rate of 116.59 mg h^-1 mg^-1 with a Faradaic efficiency of 96.46% is delivered over the optimized Ce-Fe cluster. Further applying this highly efficient NO₂RR electrocatalyst as the cathode material, a novel Zn-nitrite battery exhibits a power density of 10.78 mW cm^-2 and a Faradaic efficiency of 97.08% for NH₃ production.