Fe-doping induced morphological changes, oxygen vacancies and Ce3+–Ce3+ pairs in CeO2 for promoting electrocatalytic nitrogen fixation

Abstract

Developing active and robust catalysts for the electrocatalytic N₂ reduction reaction (NRR) represents a promising strategy for ambient NH₃ production but remains challenging. Herein, CeO₂ was modulated by Fe-doping for the NRR in neutral media. Fe-doping was found to induce the morphological change of CeO₂ from crystalline nanoparticles to partial-amorphous nanosheets which contained abundant oxygen vacancies (V_O), resulting in more exposed active sites and accelerated electron transport. Density functional theory (DFT) calculations further revealed that the coexistence of the Fe dopant and its adjacent V_O enabled the creation of Ce³⁺–Ce³⁺ pairs which served as the most active centers for effectively catalyzing the NRR and suppressing the hydrogen evolution reaction. These Fe-doping induced synergistic effects led to a significantly enhanced NRR performance of Fe-CeO₂ with an NH₃ yield of 26.2 μg h⁻¹ mg⁻¹ (−0.5 V) and a faradaic efficiency of 14.7% (−0.4 V). Therefore, this metal-doping induced multifunctionality will open up new opportunities to design powerful NRR catalysts for N₂ fixation.