A highly efficient photocatalytic H2 evolution system using colloidal CdS nanorods and nickel nanoparticles in water under visible light irradiation

A highly efficient noble-metal-free photocatalytic system in aqueous solution was developed for hydrogen evolution by visible light (≥420nm) irradiation using nanocrystal CdS nanorods photosensitizer coupled with size-controlled water-soluble Ni NPs catalyst and LA sacrificial electron donor. The highest efficiency with Ni NPs of 6nm size could reach up to 80% of Pt nanoparticles (5nm) under the same experimental conditions, which is of great value based on economic concerns that Pt is noble and far more expensive than Ni. The system demonstrated that Ni NPs had high H2 evolution efficiency with 9710TON (relative to Ni NPs) after 10h of illumination and a TOF of 1232mol H2 per mole Ni NPs per hour in the first 6h. This work demonstrates a viable strategy to achieve highly efficient hydrogen production with earth abundant inorganic catalysts in aqueous solution and provides some novel notions of efficiently harnessing solar energy for photocatalytic applications. •A noble-metal-free photocatalytic system for highly efficient hydrogen production was developed.•Nickel nanoparticles, CdS nanorods and lactic acid were catalyst, photosensitizer and sacrificial electron donor, respectively.•The system displayed highly efficient visible light (λ≥420nm) induced activity for hydrogen evolution.•The highest efficiency of Ni NPs could reach up to 80% of Pt nanoparticles under the same experimental conditions. A noble-metal-free photocatalytic system for highly efficient hydrogen production has been developed with colloidal nickel nanoparticles (Ni NPs), CdS nanorods (CdS NRs) and lactic acid (LA) as catalyst, photosensitizer and sacrificial electron donor, respectively, in aqueous solution without any organic solvent. The hydrogen evolution activity of the highly active Ni NPs (6nm) could amount to 80% of the well-known Pt nanoparticles (5nm) in equimolar amount at pH 3.0 water solution under visible light (λ≥420nm) irradiation. A maximum turnover number (TON) of 9710 based on Ni NPs (6nm) was obtained after 10h of irradiation at a catalyst concentration of 1.38×10−5M and turnover frequency (TOF) value of 1232 was achieved for the first 6h of photocatalytic reaction. A series of Ni nanoparticles colloids with different sizes plus Fe, Co nanoparticles were also tested for photocatalytic H2-evolution. The results showed the obvious effect of Ni NPs size on the hydrogen evolution activity and the smaller (6nm) Ni nanoparticles exhibited the highest activity compared with