In this study, leveraging the tunable surface groups of MXene, the two-dimensional (2D) Nb₂CT_x with [sbnd]OH terminal (NC) was synthesized. 2D ZnIn₂S₄ (ZIS) nanosheets were prepared with the aid of sodium citrate, enhancing the exposure ratio of active (1 1 0) facet. On this basis, 2D/2D ZnIn₂S₄/Nb₂CT_x  heterojunctions were fabricated to improve photocatalytic hydrogen evolution reaction (HER) performance. The optimized 6 wt% Nb₂CT_x /ZnIn₂S₄-450 (6NC/ZIS-450) photocatalyt exhibits a remarkable HER rate of 3603 μmol g^-1h^-1, which is 10 times superior to that of the original ZnIn₂S₄. Its apparent quantum efficiency (AQE) at 380 nm reaches 14.9 %. Meanwhile, even after 5 rounds of HER, the activity of 2D/2D ZnIn₂S₄/Nb₂CT_x  heterojunction remained at 90 %, far superior to that of pure ZnIn₂S₄ (34 % and 31 %). Energy band structure analysis and density functional theory (DFT) calculation indicate that Nb₂CT_x  adsorbed with [sbnd]OH exhibit a low work function. By serving as a hole cocatalyst, it effectively boosts the photocatalytic HER rate of ZnIn₂S₄/Nb₂CT_x  heterojunction and inhibits the photocorrosion of ZnInS. This unique insight, via hole transport highways and increased exposure of active facets, effectively enhances the activity and stability of sulfides photocatalysts.