Bi2MO6 (M = Mo, W) Aurivillius oxides for efficient photocatalytic N2-to-NH3 conversion: a perspective review

Abstract

The emerging technology for synthetic ammonia (NH₃), based on the photocatalytic nitrogen reduction reaction (pNRR), holds great promise for sustainable ammonia synthesis using clean solar energy with zero-carbon emissions. Nevertheless, the high bond-energy activation of inert nitrogen molecules (N₂) remains a bottleneck for pNRR catalysts. As the simplest Aurivillius oxides, Bi₂MO₆ (M = Mo, W) materials have been regarded as promising photocatalysts due to their unique layer-structural and electronic properties. In this review, for the first time, the latest research progress on Bi₂MO₆ (M = Mo, W)-based photocatalysts for N₂-to-NH₃ applications is summarized. The process and mechanism of photocatalytic nitrogen fixation have been elucidated from the adsorption, activation and hydrogenation steps of N₂-to-NH₃ conversion. In particular, the roles of defect engineering and heterojunction strategies in preparing Bi₂MO₆ (M = Mo, W) photocatalysts for the N₂-to-NH₃ reaction were elucidated, and the accuracy of ammonia nitrogen detection and its source was discussed. Finally, the future direction of photocatalytic ammonia synthesis for agricultural and industrial applications was indicated. This review emphasizes provision of forward-looking insights to inspire innovative strategies for sustainable nitrogen fixation and offers a roadmap for future advancements.