Designing “Core–Shell” Insoluble‐SiW₁₁Fe@δ‐Bi₂O₃ Z‐Scheme Heterojunction for Photo‐Driven Nitrogen Reduction Reaction and Evaluating the Impact of Oxygen toward Nitrogen Reduction

Abstract Photo‐driven nitrogen fixation is regarded as a promising sustainable strategy to generate low‐concentration NH₃/NH₄⁺. Insoluble SiW₁₁Fe@δ‐Bi₂O₃ with “core–shell” structure and Z‐scheme featured heterojunction is constructed under solvothermal conditions. Chemisorption of nitrogen improves significantly due to increased oxygen vacancies on δ‐Bi₂O₃ as induced by insoluble SiW₁₁Fe salt. Z‐scheme heterojunction is suggested according to energy diagram analyses and electron paramagnetic resonance spin‐trapping experiments, which can be well correlated to enhanced transient photocurrent and catalytic efficacy. [Ru(bpy)₃]²⁺ counter ion in the composite acts as a photosensitizer, leading to improved light harvesting. These merits account for superior performance of Ru_2.5SiW₁₁Fe@δ‐Bi₂O₃. NH₃/NH₄⁺ production rate of 121 µmol g_cat⁻¹ h⁻¹ is achieved under simulated sunlight irradiation in nitrogen atmosphere, but reduces on switching to air. The impact of oxygen over nitrogen reduction is investigated, and productions of both NH₃/NH₄⁺ and H₂O₂ are evaluated when using gas mixture feedstock with different V(N₂):V(O₂) ratios. The performance of nitrogen reduction depends mainly on its volume ratio in mixture feedstock, in addition to reduction capability of photocatalyst. By reducing the latter one appropriately, nitrogen reduction would be slightly favored when using air as feedstock.