Nanoporous Nickel-Molybdenum Oxide with an Oxygen Vacancy for Electrocatalytic Nitrogen Fixation under Ambient Conditions.

The electrochemical nitrogen reduction reaction (NRR) is regarded as a sustainable method for N2 fixation. N2 adsorption and N≡N cleavage are the main challenges for the NRR. Herein, we propose a potential approach to enhance N2 activation via introducing oxygen vacancies (OVs) into nanoporous NiO/MoO3. Nanoporous NiO/MoO3 with OVs (np-OVs-NiO/MoO3) is prepared by a two-step process of dealloying and solid-state reaction. np-OVs-NiO/MoO3 exhibits a high NH3 yield of 35.4 μg h-1 mgcat-1 and a Faradaic efficiency (FE) of 10.3% in 0.1 M PBS solution. The introduction of OVs enhances the conductivity, N2 adsorption, and catalytic performance of np-NiO/MoO3. The dual-metal sites with OVs have a unique electronic structure in favor of the "π back-donation" behavior, which decreases the energy barrier of protonation steps and improves the whole NRR process. This approach provides new insight into the design of composite transition metal oxides with OVs for the NRR catalyst under ambient conditions.