Vacancy engineering of oxidized Nb2CTx MXenes for a biased nitrogen fixation

The artificial nitrogen (N2) reduction reaction (NRR) via electrocatalysis is a newly developed methodology to produce ammonia (NH3) at ambient conditions, but faces the challenges in N2 activation and poor reaction selectivity. Herein, Nb-based MXenes are developed to remarkably enhance the NRR activity through the engineering of the stretched 3D structure and oxygen vacancies (VO). The theoretical studies indicate that N2 could be initially adsorbed on VO with an end-on configuration, and the potential determining step might be the first hydrogenation step. The catalysts achieve an NH3 production rate of 29.1 mg h 1 mgcat �1 and excellent Faradic efficiency of 11.5%, surpassing other Nbbased catalysts. The selectivity of NRR is assigned to the unique structure of the catalysts, including (1) the layered graphitic structure for fast electron transfer and active site distribution, (2) the reactive VO for N2 adsorption and activation, and (3) the expanded interlayer space for mass transfer.& COPY; 2022 Institute of Process Engineering, Chinese Academy of Sciences. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co., Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

Nb-based MXenes are developed to enhance the NRR activity and achieve efficient conversion of nitrogen into ammonia through the engineering of the stretched 3D structure and oxygen vacancies. The catalysts show high ammonia production rate and excellent Faradic efficiency, and the selectivity is attributed to the unique structure including layered graphitic structure, reactive oxygen vacancies, and expanded interlayer space.