Electron and Hydrogen Dual Spillover at CeO2/Fe3C Interfaces for Efficient NH3 Electrosynthesis and High-Performance Zn-NO3 - Batteries.

The electrocatalytic nitrate reduction reaction (NO3RR) offers a sustainable route for ambient ammonia synthesis but is hindered by insufficient active hydrogen (*H) supply and strong adsorption of oxygen-containing intermediates. Herein, we propose an electron- and hydrogen-dual-channel interfacial engineering strategy by constructing a heterojunction of grain-boundary-rich CeO2 intimately interfaced with Fe3C on nickel foam (CeO2/Fe3C@NF). Oxygen-vacancy-rich CeO2 with reversible Ce3+/Ce4+ redox pairs serves a dual function: it donates electrons to Fe3C, downshifting the d-band center of Fe sites to weaken intermediate adsorption and mitigate surface poisoning; and it facilitates water dissociation to generate *H, which spills over onto Fe3C to ensure adequate *H supply for hydrogenation. Benefiting from this dual spillover mechanism, CeO2/Fe3C@NF achieves an exceptional NH3 electrosynthesis rate of 1.343 mmol h-1 cm-2 with a Faradaic efficiency of 97.04% at -0.3 V vs. RHE in an H-type cell, ranking among the best non-precious NO3RR electrocatalysts. Furthermore, a rechargeable Zn-NO3 - battery using CeO2/Fe3C@NF as the cathode delivers a power density of 8.93 mW cm-2 and stable operation over 100 h. This work establishes an electron- and hydrogen-dual-channel paradigm for rational design of efficient NO3RR electrocatalysts.