A Schottky junction is an ideal candidate for photocatalytic H 2 evolution since the photo-induced charge kinetics of semiconductors can be harnessed via coupling with metals. In this work, the ZnIn 2 S 4 semiconductor and metallic MoO 2 are successfully integrated to form a composite photocatalyst, which is analogous to the conventional metal−semiconductor Schottky junction. In such a heterojunction, hierarchical ZnIn 2 S 4 flower-like structures are in situ grown on MoO 2 nanosheets. The experimental and computational results suggest that the Schottky barrier successfully suppresses the recombination of photocarriers, while MoO 2 further extends the spectral range of light absorption and decreases the activation energy of H 2 evolution. As a result, the optimal MoO 2 /ZnIn 2 S 4 composite exhibits a 28.2 times higher H 2 evolution rate (3730.5 μmol/g/h) than pristine ZnIn 2 S 4 under visible light.