Abstract In this paper, nanosized Zn x Cd 1‐ x S is synthesized by a simple hydrothermal method and modified by amorphous CoB. Zn x Cd 1‐ x S/CoB Schottky heterojunction composite photocatalyst is reasonably designed. The adhesion of tiny Zn x Cd 1‐ x S nanoparticles to irregular block CoB is more conducive to the dispersion of Zn x Cd 1‐ x S and better interface connection between catalysts, thus further promoting the migration of photogenerated carriers, protecting the photocorrosion of Zn x Cd 1‐ x S, and finally improving the efficiency of photocatalytic hydrogen production. The composite catalyst Zn x Cd 1‐ x S/CoB‐20 means that the loading content of CoB is 20 wt%, and the photocatalyst has the highest catalytic efficiency under visible light, reaching 1494.09 µmol within 5 h. Through the characterization of XRD, XPS, electrochemical and optical properties of the catalyst, it is proved that the introduction of CoB can significantly inhibit the recombination of photogenerated electron holes and enhance the response to visible light. This study provides a feasible scheme for co‐catalysts to replace precious metal catalysts and effectively reduce Zn x Cd 1‐ x S photocorrosion.