Plasmonic Bi-doped Bi-Bi2Sn2O7/Bi-g-C3N4 photothermal catalysis for nitrogen fixation

Abstract

Compared to photocatalysis, photothermal catalysis offers the advantage of harnessing a broader light spectrum while integrating thermal energy to significantly enhance reaction rates. In this work, a plasmonic Bi-doped Bi₂Sn₂O₇ (Bi-Bi₂Sn₂O₇) photothermal catalyst was successfully formulated through an in situ solvothermal method and further combined with Bi-doped g-C₃N₄ (Bi-g-C₃N₄). The plasmon resonance effect of Bi and the formation of Bi–O defects significantly enhanced the light absorption capacity and photothermal effect of the catalyst, thereby effectively promoting the ammonia synthesis reaction. Upon visible-light and full-spectrum irradiation, the optimized Bi-Bi₂Sn₂O₇/Bi-g-C₃N₄ composite catalyst achieved ammonia yields of 486.14 μmol g_cat⁻¹ h⁻¹ and 699.76 μmol g_cat⁻¹ h⁻¹, respectively. In situ XPS, DFT calculations and band structure analysis additionally elucidated the charge transfer mechanism occurring throughout the reaction. Hydroponic experiments of marsh pennywort were carried out on ammonia fertilizer obtained by using sunlight, air and the photocatalyst. Satisfactory results were obtained for the growth of the plant. The toxicity of bismuth-based photocatalysts was investigated in aqueous solution for the first time. This study offers new perspectives and potential applications for the efficient realization of photothermal catalytic ammonia synthesis.