One-step hydrothermal synthesis of novel flower-like Bi2Mn4O10 anchored on BiOI1−xBrx nanosheets for efficient photocatalytic nitrogen fixation

The reduction of nitrogen molecules (N ₂) to ammonia (NH ₃ ) is a promising method for energy sources and chemical manufacturing, owing to its sustainability and environmentally friendly process. The photocatalytic nitrogen reduction reaction (PNRR) is particularly recognized as a potential synthesis method. In this study, we developed n-type flower-like of Bi ₂Mn ₄O ₁₀ (BiMnO) nanoparticles in different percentages (5%, 10%, 15%, and 20%) anchored on the surface of n-type BiOI _0.6Br _0.4 (BiOIBr) nanosheets to form a heterojunction 5–20-BiMnO/BiOIBr using one-step hydrothermal method. According to Mott-Schottky plot analysis, BiMnO has a low Fermi level than BiOIBr, leading to spontaneous electron transfer from BiOIBr to BiMnO. In contrast, holes move in the opposite direction, forming a type-II heterojunction. Electrochemical impedance spectroscopy, linear sweep voltammetry, cyclic voltammetry, and transient photocurrent tests demonstrated that the 10-BiMnO/BiOIBr heterojunction is highly effective in the spatial separation photogenerated electron-hole pair due to the synergetic impact of the energy-level discontinuity at the interface. Consequently, outstanding N ₂ reduction activity was achieved under simulated solar light, with an NH ₃ production yield of 6.2 mmol g ⁻¹ over a 4-h run, significantly higher than that of pristine BiMnO and the solid solution of BiOIBr in 10% methanol aqueous solution. This work provides a systematic method for the fabrication of novel and efficient heterojunctions for nitrogen fixation.