We report a new Pd7P3 cocatalyst that significantly enhances H-2 production performance and durability for water splitting under visible light radiation (lambda >= 450). The 3 wt% Pd7P3/CdS compared with pure CdS had a 30-fold larger H-2 production amount (302860 vs. 10126 mu mol/g) and 39-fold larger average H-2 production rate (41645 vs. 1066 mu mol/g/h) after 10 h of visible light radiation. The 3 wt% Pd7P3/CdS had an apparent quantum yield of 35.1% after 72 h. The lifespan and reuse cycle tests on the 3 wt% Pd7P3/CdS showed that addition of Pd7P3 into CdS enhanced H-2 production ability and reusability in photocatalytic water splitting. The photoluminescence and photocurrent tests showed the Pd7P3 cocatalyst extracted photoelectrons from the CdS bulk under visible light radiation, then those photoelectrons migrated to the Pd7P3/CdS interfaces and reacted with the H+ adsorbed on the catalyst surface, producing abundant H-2. Therefore, the addition of Pd7P3 improves the movement of photoelectrons, separation of photo-generated electron-hole pairs, and photoelectron utilization efficiency, thus significantly enhancing the photocatalytic H-2 production ability.