Bismuth-rich Bi₁₂O₁₇Cl₂ nanorods engineered with oxygen vacancy defects for enhanced photocatalytic nitrogen fixation

Abstract

Ammonia (NH3) is an indispensable chemical that serves as a key precursor in the production of a wide array of commercially essential nitrogenous compounds. The catalytic conversion of nitrogen (N2) to NH3 is a kinetically complicated and energetically demanding reaction. In this regard, the inception of photocatalytic N2 fixation which operates under mild conditions holds great promise as a sustainable alternative to the conventional Haber-Bosch process. Herein, defective bismuth-rich oxychloride with oxygen vacancies (BOC-OV) was synthesized and optimized for N2 photo-fixation. The fabrication encompassed a two-step hydrothermal and post-synthesis inert annealing for the induction of oxygen vacancies (OVs). Through the introduction of OVs, the bismuth-rich photocatalyst garnered a massively improved photo-absorption range, enhanced charge dynamics, and increased efficiency of charge separation. The defects generated also provided an abundance of active sites to ease N2 adsorption and overcome the energy barrier for the activation of N2 molecules. The defect-rich BOC-OV sample exhibited a notable NH3 generation rate of 23.43 µmol gcat-1 h-1 in pure water under solar irradiation. On the basis of the experimental findings, this study discloses insights into the rational engineering of OVs and presents the OV-induced bismuth-rich oxychloride as a promising material for the realization of a highly efficient and sustainable photo-driven N2 fixation system.