Synthesis, Properties, and Photocatalytic Hydrogen Production of G‐C ₃ N ₄ /MXene Composites: A Review

ABSTRACT The increasing global energy demand for clean energy, combined with the depletion of fossil fuels and rising environmental pollution, has driven the search of sustainable energy solutions. Photocatalytic hydrogen (H 2 ) production using solar energy offers a promising pathway for clean fuel generation. Among various photocatalysts, graphitic carbon nitride (g‐C 3 N 4 ) has attracted attention due to its appropriate band structure, chemical stability, and metal‐free composition. However, limitations such as low surface area, rapid charge carrier recombination, and narrow light absorption spectrum limit its efficiency. To address these issues, g‐C 3 N 4 /MXene composites have emerged as advanced photocatalytic materials. MXenes, a family of two‐dimensional (2D) transition metal carbides/nitrides, possess high electrical conductivity, tunable surface functionalities, and excellent interfacial compatibility with g‐C 3 N 4 . This review highlights various synthesis strategies, including polymerization, electrostatic self‐assembly, solution mixing, and calcination for fabricating g‐C 3 N 4 /MXene heterostructures. The improved physiochemical properties such as enhanced charge transport, increased active surface sites, extended visible‐light absorption, and photostability are systematically discussed. Special emphasis is placed on advanced characterization techniques such as X‐ray diffraction (XRD), Scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FT‐IR) which are essential for probing the crystallinity, morphology, chemical states, and functional group of the composite material. Moreover, the photocatalytic performance of g‐C 3 N 4 /MXene composites in H 2 evolution is explored, supported by recent density functional theory (DFT) studies that provide mechanistic insight into charge transfer and active site interactions. The review concludes by outlining current challenges and proposing future research directions, including surface engineering, interface modulation, and computational design, to further optimize g‐C 3 N 4 /MXene photocatalysts for efficient and scalable H 2 production.