Bi ₂ MoO ₆ /Bi ₂ MoO _{6– x} S-Scheme Homojunction for Efficient Photocatalytic N ₂ Reduction

Abstract

Ammonia is in high demand and widely used, yet its production still predominantly relies on the energy-intensive Haber-Bosch process, highlighting the urgent need for a milder alternative technology. Photocatalytic N₂ fixation shows great promise in this regard despite the challenge of developing high-efficiency catalysts. In this study, we successfully prepared micronano spherical Bi₂MoO₆/Bi₂MoO_6-x S-Scheme homojunctions using a simple solvothermal-calcination coupling method, which offer unique advantages for nitrogen fixation catalysis: (i) the micronano structure mitigates the agglomeration issue common in nanomaterials, thereby exposing more active sites; (ii) the in situ constructed S-Scheme homojunction features a high-quality surface and interface structure, enhancing the spatial separation and transport of photogenerated charges and preserving strong redox capabilities; and (iii) the oxygen-rich vacancy structure promotes the N₂ adsorption and activation. Thanks to those favorable properties, the Bi₂MoO₆/Bi₂MoO_6-x (BMO/BMO_OV) S-Scheme homojunction demonstrates exceptional ammonia production efficiency, with a NH₄⁺ generation rate of 238.7 μmol g^-1 h^-1 under simulated sunlight, which is over 5.2 times higher than that of pristine Bi₂MoO₆ (BMO) and significantly outperforms other reported similar catalytic systems (see Table S1). This work introduces a simple and versatile method for synthesizing homojunctions, potentially inspiring the development of more efficient photocatalysts for nitrogen fixation and beyond.