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 gC3N4/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