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.

g-C3N4-based Z-scheme photocatalysts towards energy and environmental applications.

No abstract

Interface engineering is a vital concern to achieve high efficiency in heterojunction photocatalysts. The judicious design of efficient interfacial electron mediators to accelerate the charge transfer efficiency in Z-scheme heterojunctions with interfacial contact for enhancing the performance of photocatalysts is essential and has been considered an immense challenge. Inspired by nature, multivariate all-solid-state Z-scheme TiO2@Ti3C2/MIS heterojunction composites were fabricated via a simple two-step oxidation strategy for highly promoted multiple photocatalytic applications. The morphological analysis of TiO2@Ti3C2/MIS composites demonstrated that MgIn2S4 (MIS) microflowers were accumulated on the surface of Ti3C2@TiO2 nanosheets, providing dense active sites to the MIS microflowers for efficient photocatalytic applications. The HRTEM and XPS characterization distinctly clarified the close interfacial interaction between MIS with Ti3C2 and TiO2. The optimized TiO2@Ti3C2/MIS-15 photocatalysts exhibited the highest photocatalytic ciprofloxacin degradation (92%) and hydrogen evolution (520.3 μmol h–1) as compared to those of their pristine counterparts. From the mechanistic insights, the charge migration pathway was observed between MIS and TiO2, where Ti3C2 nanosheets served as an electron bridge in constructing the Z-scheme and thus extended the lifetime of the charge carriers photoinduced by MIS and TiO2. The significant participation of •O2 – and •OH radicals during photocatalytic CIP degradation was verified by active species trapping experiments, EPR, and liquid chromatography–mass spectrometry (LC-MS) analysis. The current study provides a strategy to design mediator-based Z-scheme heterojunction interfaces for improving the catalytic activity of MXene-derived photocatalysts.

Spatial charge separation and migration are the critical shortcomings dominating the core energy conversion corridors of photocatalytic systems. Here, a biomimetic multi-interfacial architecture providing strong coupled interaction and rapid charge transmission for photostable and competent photocatalytic H2O2 production and H2 evolution is proposed. The triple-hybrid all-solid-state Z-scheme system was formed with the (001) facet exposed TiO2 nanosheets derived from MXene layers and B-g-C3N4 nanosheets (M/(001)TiO2@BCN) through an electrostatic self-assembly strategy with intimate electronic interaction due to Ti orbital modulation and proper stacking among the hybrids. The metallic and highly conductive MXene layers act as solid state electron mediators in the Z-scheme heterojunction that promote electron–hole separation and migration efficiency. Specifically, the MTBCN-12.5 composite provides optimum yield of H2O2 up to 1480.1 μmol h–1 g–1 and a H2 evolution rate of 408.4 μmol h–1 (with ACE 6.7%), which are 4 and 20 fold greater than the pristine BCN, respectively. The enhanced photocatalytic performance is systematically identified by the increased surface area, higher cathodic and anodic current densities of −1.01 and 2.27 mA cm–2, delayed charge recombination as supported by PL and EIS measurement, and excellent photostability. The Z-scheme charge transfer mechanism is validated by time-resolved photoluminescence (TRPL) analysis, cyclic voltametric analysis, and the radical trapping experiment as detected by PL analysis. This research marks a substantial advancement and establishes the foundation for future design ideas in accelerating charge transfer.