In this work, graphene(GP) supported Co–Mo–P catalysts for H₂ generation were prepared via an in-situ synthesis strategy with the help of photogenerated electrons. The transmission electron microscopy images (TEM) of the catalysts indicated that the elements of Co, Mo and P were distributed in a relatively homogeneous manner in the catalysts. The Co–Mo–P/GP catalyst exhibited high photocatalytic activity for hydrogen generation sensitized by Eosin Y (EY) under visible light. The Mo/(Co + Mo) molar ratio (χ_Mo) was varied in the catalyst to study the effect of Mo doping on the catalytic efficiency. The highest rate of the H₂ generation was found to be as high as 33.3 mmol·h⁻¹·gCo⁻¹ when the χ_Mo was 10%. The apparent quantum efficiency (AQE) of the reaction over the Mo doped catalyst under 430 nm irradiation was 52.6%, which was six times higher than that using the un-doped Co–P/GO catalyst.