Mannitol and acidity co-tuned synthesis of oxygen-vacancy-modified bismuth molybdate nanorods for efficient photocatalytic nitrogen reduction to ammonia

Oxygen vacancies (Ovs) in semiconductors, which can adsorb and activate N-2 molecules, are active sites for photocatalytic nitrogen reduction to ammonia. However, simple and effective methods for creating Ovs still need to be explored. Herein, mannitol was used to selectively create Ovs at Mo in Bi2MoO6 (BMO) and form BMO short nanorods (SNRs) through a hydrothermal process, with the Ov content, SNR size, and surface area of the sample effectively tuned by pH. BMO SNRs containing the most Ovs exhibit the highest visible light absorption, fastest photoexcited charge separation, and best photocatalytic nitrogen fixation performance, with an N-2 reduction reaction rate in pure water reaching approximately 107-fold that of BMO nanosheets synthesized in the absence of mannitol, and an apparent quantum yield of 2.78% at 420 nm, superior to all of the reported BMO-based photocatalysts. This work provides a new and simple method for selective Ov creation and the morphological tuning of BMO to expedite the photocatalytic N-2 reduction.

Automated summary

It was found that mannitol could be used to selectively create oxygen vacancies (Ovs) in Bi2MoO6 (BMO) and form short nanorods (SNRs), and the Ov content, SNR size, and surface area of the sample could be effectively tuned by pH. BMO SNRs containing the most Ovs exhibited the best performance in terms of visible light absorption, photoexcited charge separation, and photocatalytic nitrogen fixation. This work provides a new and simple method for selective Ov creation and morphological tuning of BMO to facilitate photocatalytic N-2 reduction.