Hybrid photocatalytic H ₂ evolution systems containing xanthene dyes and inorganic nickel based catalysts

The application of nickel based earth abundant inorganic solids as catalysts in xanthene dye sensitized systems was evaluated for photocatalytic H ₂ production from water. The introduction of heterogeneous nanoparticles into molecular systems as catalysts is the conceptual begin to broaden the construction of photocatalytic H ₂ production systems. A series of Ni based inorganic nanoparticles, including Ni metal, NiO, NiS and NiSe, are capable of producing H ₂ from triethanolamine sacrificial aqueous solution when photosensitized by xanthene dyes. NiS catalysts synthesized from different methods were also evaluated for H ₂ production performance. The best H ₂ production result is obtained with the use of Erythrosin Y as the photosensitizer and NiS synthesized in ethylene glycol as the catalyst. This system is active even under photons with wavelengths longer than 520 nm with a H ₂ production of 2.5 mmol within 26 h of irradiation from a 300 W Xenon lamp. Meanwhile, it can generate over 4.2 mmol of H ₂ within 16 h of irradiation with a 440 nm long-pass cut-off filter. Within the visible light range we examined, the highest quantum efficiency is around 15% at 520 nm. The high activity of NiS could be contributed by its high electrochemical activity, metallic nature, unsaturated Ni environment and suitable Fermi energy level. These hybrid systems consist of earth abundant elements, and the catalyst is photostable and recyclable compared to homogeneous metal complex catalyst.