The generation of hydrogen (H sub(2)) through photocatalytic water splitting by employing various cocatalysts has attracted much attention. Herein we report for the first time that metallic molybdenum phosphide (MoP), as a highly active cocatalyst, can significantly enhance photocatalytic H sub(2) production from water. A series of MoP/CdS nanorod (NR) hybrids were facilely prepared. The optimal amount of MoP led to a maximal H sub(2) evolution rate of 163.2 mu mol h super(-1) mg super(-1) under visible light illumination ( lambda > 420 nm), which is more than 20 times higher than that of freshly prepared CdS NRs. This work demonstrated that the suitable Fermi level alignment of MoP and CdS is responsible for the high photocatalytic activity of H sub(2) production under visible light in the present system, as evidenced by both experimental and theoretical results.