Dual-site catalysis with engineered electronic interaction in Fe-doped CeO2/FeNC composites for nitrate reduction to ammonia

Single-atom catalysts (SACs) and metal oxides exhibit distinct advantages in nitrate reduction reaction (NO3RR), yet their intrinsic limitations, such as suboptimal adsorption-energy scaling, metal aggregation, and poor conductivity, have hindered practical applications. To address the challenges, we design a heterostructured Fe-doped CeO2/FeNC dual-site catalyst, synergizing atomic Fe sites and oxygen-deficient CeO2 to enhance NO3RR performance. This design synergistically couples atomic Fe sites and oxygen-deficient CeO2 to engineer the local electronic structure and interfacial charge transfer, thereby enhancing NO3RR performance. The FeNC component, with its well-defined d-band electronic structure, ensures efficient NO3− activation by optimizing adsorption energetics. Meanwhile, the introduction of Fe-doped CeO2 introduces abundant oxygen vacancies, which act as electron trapping centers, and establishes reversible Ce3+/Ce4+ redox couples. These features collectively serve as dynamic electron reservoirs, modulating the charge distribution at the interface and accelerating reaction kinetics by facilitating electron–proton transfer. Importantly, the optimized catalyst achieves a 1.55-fold increase in ammonia yield and a 1.18-fold enhancement in Faradaic efficiency at −0.9 V vs RHE compared to pure FeNC. When applied in a Zn-NO3− battery, the catalyst delivers a peak power density of 2.31 mW cm−2, surpassing the FeNC-based system. This work highlights the critical role of integrating SACs with doped metal oxides to engineer the local electronic structure and interfacial charge transfer of multifunctional electrocatalysts for sustainable energy conversion.