Design of Three-Dimensional Hollow-Sphere Architecture of Ti₃C₂T_x MXene with Graphitic Carbon Nitride Nanoshells for Efficient Photocatalytic Hydrogen Evolution

Photocatalytic water splitting is the most environmentally friendly method to generate energy. Despite intense research in this area, rapid charge-carrier recombination and limited light absorption of semiconductor-based photocatalysts remain key challenges. Herein, protonated g-C3N4/Ti3C2Tx MXene hollow spheres, fabricated by electrostatic layer-by layer assembly and a sacrificial template, were used for effective photocatalytic hydrogen (H2) evolution. The constructed three-dimensional (3D) hollow spheres exhibited enhanced light absorption, a two-dimensional (2D) heterostructure to shorten the electron migration distance, a Schottky junction to facilitate separation and transfer of charge carriers, and high specific surface area for efficient H2 adsorption. The optimal formulation had an H2 production rate of 982.8 μmol g–1 h–1, which is more than 3.5-fold higher than the H2 production rate of pure protonated g-C3N4 and 1.22-fold higher than the H2 production rate of protonated g-C3N4/Ti3C2Tx, which lacks the hollow structure. This unique 3D heterojunction structure made from 2D materials improved photocatalytic H2 production performance and can be readily extended to other reactions.