Development of MgIn₂S₄ Microflower-Embedded Exfoliated B-Doped g-C₃N₄ Nanosheets: p–n Heterojunction Photocatalysts toward Photocatalytic Water Reduction and H₂O₂ Production under Visible-Light Irradiation

In recent years, designing a highly efficient, cost-effective, and persistent photocatalyst to annihilate world’s major ongoing challenges has been a hot topic in the research community. Herein, we have developed a microflower-like morphology of MgIn2S4 (MIS) through a simple hydrothermal method without using any surfactants. A series of MIS-modified exfoliated B-doped g-C3N4 (e-BCN) nanocomposites have been synthesized and characterized by powder X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, UV–vis diffuse reflectance spectroscopy, photoluminescence (PL), electrochemical impedance spectroscopy (EIS), and Mott–Schottky analyses to study their structural, optical, and electrochemical properties. The morphological analyses of MIS/e-BCN composites demonstrated that the MIS microflowers are deposited on the surface of the e-BCN nanosheet, which provides a large number of active sites to the MIS microflowers for the better adsorption of water molecules. XPS and morphological results distinctly evidenced the close interaction between e-BCN and MIS. The results from PL and EIS analyses revealed the deteriorated recombination rate of e–/h+ pairs with reduced charge-transfer resistance of MIS/e-BCN heterojunction photocatalysts. The MIS/e-BCN composite with 10 wt % of MIS (MSBCN-10) exhibited the highest photocatalytic H2 generation rate with an apparent conversion efficiency of 5.27%. A stupendous production efficiency of H2O2 was also observed for the MSBCN-10 composite in the presence of O2-saturated water and ethanol under visible-light illumination. The current study paves an astonishing strategy to design a metal sulfide-modified g-C3N4-based photocatalyst toward photocatalytic applications.