Titanium Carbide MXenes Cocatalyst with Graphitic Carbon Nitride for Photocatalytic H2 Production, CO2 Reduction, and Reforming Applications: A Review on Fundamentals and Recent Advances

Two-dimensional (2D) titanium carbide (Ti 3 C 2 ) MXenes have gained increasing attention in photocatalytic applications due to their prominent electrical conductivity, optical properties, and abundant surface functional groups. The unique layered microstructure characteristics of Ti 3 C 2 provide a large surface area, interlayer spacing, and hydrophilic surface functional groups, contributing to their high photocatalytic efficiency. Graphitic carbon nitride is very promising among the semiconductors due to its layered structure and higher reduction potential. The present study discusses the recent advances in various Ti 3 C 2 structures coupled with g-C 3 N 4 for hydrogen evolution reactions (HER), photocatalytic CO 2 reduction reactions (CO 2 RR), and CO 2 reforming of methane (CO 2 RM). Initially, we provide an overview of the fundamental properties of Ti 3 C 2 -based composites and recent synthesis approaches, including structure development, of functional group formation, and various etching agents. We further explore using Ti 3 C 2 in different structures coupled with g-C 3 N 4 as a binary and ternary composite with the involvement of other semiconductors and sensitizers. The performance of various composites for water splitting to produce hydrogen and reforming systems, including CO 2 conversion with H 2 O, CO 2 methanation, dry reforming of CH 4 (DRM), and bireforming of CH 4 (BRM), is discussed in detail. The hydrophilic surface functional groups and efficient electron transport pathways of Ti 3 C 2 MXenes make them excellent candidates for catalysts with high yield rates and selectivity. Finally, this review provides valuable insights into the potential applications of Ti 3 C 2 -based composites, and future research directions in this field are proposed.