Simultaneous Activation of N2 and H2O by Bi and O Double Vacancies in Bi2WO6 for Photocatalytic Ammonia Synthesis

Photocatalytic nitrogen reduction to ammonia intrinsically relies on the synergistic activation of both N2 and H2O molecules by the catalyst. However, achieving simultaneous and efficient activation of these two species on a single catalyst surface remains a formidable challenge, constrained by poor N2 adsorption and the high dissociation energy barrier of the N≡N triple bond. To address this, a vacancy engineering strategy was adopted to design and fabricate a Bi2WO6 photocatalyst featuring both bismuth and oxygen dual vacancies (VBi+O-BWO). The oxygen vacancies trap photogenerated electrons for N2 activation, while bismuth vacancies enhance H2O adsorption and facilitate proton generation. Through this synergistic effect, the photocatalytic nitrogen reduction performance was significantly enhanced. Experimental results show that VBi+O-BWO achieves an ammonia production rate of 113.14 μmol·g-1·h-1, a 4.9-fold enhancement over the unmodified catalyst. N2-TPD results demonstrate that the dual vacancies effectively enhance N2 chemisorption, facilitating subsequent activation. In situ FTIR confirms that N2 adsorbs and converts on Bi2WO6 via a distal pathway. This study provides new insights into the development of high-efficiency dual-vacancy photocatalytic materials.