Boosted N₂ Activation through 4f-2p-3d Orbital Hybridization for Efficient Nitrate Electrosynthesis

The electrochemical N-2 oxidation reaction (NOR) has emerged as a promising approach for achieving high selectivity in nitric acid (HNO3) production. However, the sluggish N-2 activation process in NOR due to the high cleavage energy barrier of the N & EQUIV;N bond remains a challenge. Herein, a novel orbital hybridization strategy for tuning the NOR performance through the construction of cerium (Ce) 4f-O 2p-Co 3d network in Ce-doped Co3O4 (Ce-Co3O4) is proposed. The Ce-Co3O4 catalyst exhibits an enhanced HNO3 yield of 24.76 & mu;g h(-1) mg(cat)(-1) and a promoted Faradaic efficiency of 31.93% in 0.1 m Na2SO4 electrolyte under ambient conditions compared to those of the pure Co3O4 (13.75 & mu;g h(-1) mg(cat)(-1) and 23.43%). Density functional theory caculations demonstrate the strong 4f-2p-3d orbital hybridization and electron transfer in Ce-Co3O4. Moreover, a series of in situ techniques provide direct evidence of stronger adsorption peaks for CoN bond and the key intermediate *NO formed after N-2 activation on the surface of Ce-Co3O4. This work provides a promising route for the preparation of efficient NOR catalysts and sheds light on the mechanism of N-2 activation through orbital hybridization.