Plasma Ag nanoparticles loaded on Bi2MoO6 to enhance surface oxygen vacancies for efficient nitrogen conversion to ammonia

Abstract

Photocatalytic nitrogen fixation reactions based on Bi₂MoO₆ (BMO) still suffer from great challenges, which need to be overcome by enhancing the visible light absorption and photogenerated carrier separation rate, as well as enriching the active sites. Herein, the photocatalytic nitrogen fixation activity of BMO was improved by Ag metal loading and enhanced oxygen vacancies (O_v). A novel Ag metal-loaded Bi₂MoO₆ (Ag/BMO) composite with enhanced O_v was designed and synthesized by a simple two-step solvothermal method using ethylene glycol as the chemical reduction reagent. Ag metal nanoparticles (Ag NPs) were homogeneously dispersed on the surface of BMO, as confirmed by TEM analysis. The Ag metal was in close contact with BMO, resulting in the formation of a Schottky junction in their contact regions. Under visible light irradiation, 1% Ag/BMO exhibited an excellent photocatalytic nitrogen fixation activity of 247.45 μmol h⁻¹ g_cat⁻¹ (6 folds greater than that of pure BMO). The results indicated that lower concentrations of Ag NPs loaded on BMO were more favourable for the photocatalytic nitrogen fixation reaction. Multiple techniques including XRD, Raman spectroscopy, XPS, SEM, TEM, UV-vis DRS, PL, TRPL, EIS, and SPV were used to reveal the origin of high performance. The significantly improved photocatalytic nitrogen fixation performance was mostly ascribed to the surface plasmon resonance (SPR) effect of Ag NPs. The loading of Ag NPs broadened the range of light absorption, and as electron trapping agents, they improved the separation efficiency of photogenerated carriers. Furthermore, the loading of Ag NPs could enhance the O_v concentration of BMO, which is another reason for the enhanced photocatalytic activity. This work offers new ideas for precious metal loading modification of BMO and its application in efficient photocatalytic nitrogen fixation reactions.