Highly Efficient Electrocatalytic Nitrate-to-Ammonia Conversion Enabled by Ce-O-Co Conjugated Active Sites in Con-CeO2/NC.

Here, an optimized Con-CeO2/NC catalyst was ingeniously constructed, in which the Ce 4f-O 2p-Co 3d conjugated active structure effectively optimized the Co 3d orbital configuration for enabling high electrocatalytic activity. This modified catalyst delivers an impressive ammonia (NH3) Faradaic efficiency of 97.19% at -0.1 V and a large NH3 yield of 0.278 mmol h-1 cm-2 at -0.5 V. Moreover, the Con-CeO2/NC-based Zn-NO3 - battery also exhibits superior electrochemical performance. Experimental results and theoretical calculations indicate that under directional electronic coupling interactions that Ce transfers charge to Co, the number of unpaired electrons in the Co 3d orbital increases, thereby altering its spin environment. Optimized Co site, with its strong electron-donating ability, not only stably adsorbs NO3 - that effectively lower its π* energy level, but also elevates the energy of the Co d orbitals electrons, bringing them closer to the π* of NO3 -. On this basis, Con-CeO2/NC promotes the electron transfer to the π* orbital of NO3 -, which increases the electron density of the Π4 6 bond of NO3 - and weakened its stability, thus effectively expediting the cleavage of the N─O bond. This study demonstrated the efficient activation of NO3 - induced by conjugated active sites, thereby providing a viable development pathway for high-performance NO3 -RR electrocatalysts.