Oxygen Vacancy Regulation Strategy Promotes Electrocatalytic Nitrogen Fixation by Doping Bi into Ce-MOF-Derived CeO₂ Nanorods

Abstract

Although the mature Haber–Bosch process has become the main method for ammonia production, its high energy consumption nature has motivated people to learn about nitrogenases, which can fix N2 in the atmosphere to NH3 under ambient conditions. Here we show that Bi-CeO2 nanorods with oxygen vacancies can effectively fix N2 to NH3 under ambient conditions by an electrocatalytic nitrogen reduction reaction (NRR). Bismuth has a certain electrocatalytic nitrogen reduction effect because of the strong force between the Bi 6p band and the N 2p orbital. The subsequent one-pot solvothermal method ensure the successful doping of Bi into the CeO2 structure, and the catalyst material Bi-CeO2 has sufficient adhesion with the substrate carbon paper, thereby ensuring electrode stability. Meanwhile, the introduction of a Bi atom to CeO2 is an effective strategy to increase the abundance of oxygen vacancies in CeO2 for the rate-determining step and hence better promote NRR activity compared with classic transition-metal catalysts because the electrons trapped by the oxygen vacancies present in the catalyst material can be injected into the counterbond orbitals of N2 adsorbed on the catalyst material, thereby weakening the N≡N triple bond for later activation and hydrogenation. The catalyst achieves a high RNH3 of 6.29 μg h–1 cm–2 with a Faradaic efficiency (FE) of 8.56% at −0.5 V (vs RHE) in 0.5 M K2SO4 at room temperature. This Article provides a new avenue for the design and development of efficient catalysts for the electrocatalytic NRR.