Enhancing the Electrochemical Nitrate‐to‐Ammonia Performance on Co ₃ O ₄ via 4 <i>f</i> ‐2 <i>p</i> ‐3 <i>d</i> Orbital Hybridization Engineering

Abstract Co 3 O 4 ‐based nanomaterials have been widely applied as electrocatalysts for nitrate reduction (NO 3 ‒ RR) to ammonia (NH 3 ); however, their performance is still unsatisfactory. Here, an attempt is made to increase the NO 3 ‒ RR performance of Co 3 O 4 via rare‐earth (denoted RE) metal‐induced 4 f ‐2 p ‐3 d orbital hybridization. By introducing various single‐atom RE metals (i.e., Y, La, Pr, and Sm) into the octahedral location, the 4 f ‐2 p ‐3 d orbital hybridization can be well regulated to optimize the 3 d orbital configuration of Co 3 O 4 . Consequently, optimum Pr‐doped Co 3 O 4 displays a 3.2‐fold increase in activity for NO 3 ‒ RR to NH 3 compared with its counterpart without Pr. Mechanistic studies combining operando experiments and theoretical calculations reveal that the Pr not only assists Co in adsorbing NO 3 ‒ but also induces 4 f ‐2 p ‐3 d orbital hybridization to increase the * NO adsorption strength and promote electron transfer from Co to * NO, thereby markedly boosting the rate‐determining step of NO 3 − RR. This study provides a new pathway to improve the performance of NO 3 − RR to NH 3 by using the f ‐ p ‐ d orbital hybridization.