Enhanced visible light-driven hydrogen production from water by a noble-metal-free system containing organic dye-sensitized titanium dioxide loaded with nickel hydroxide as the cocatalyst

Abstract

Platinum is an excellent catalyst for hydrogen production but its application is limited by the high cost. In this present paper, a series of noble-metal-free nickel hydroxide/titanium dioxide (Ni(OH)2/TiO2) nanocomposites have been synthesized and characterized. Photocatalytic hydrogen production was observed in a system containing Eosin Y-sensitized Ni(OH)2/TiO2 photocatalysts in the presence of triethanolamine (TEOA) as a sacrificial reagent under visible light (λ>420nm). The resulting photocatalysts were well characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis spectroscopy (UV–vis), and X-ray photoelectron spectroscopy (XPS). The results revealed that dye-sensitized Ni(OH)2/TiO2 material has much higher photocatalytic activity than dye-sensitized TiO2 sample, indicating the important catalytic role of Ni(OH)2. The amount of the loaded cocatalyst significantly affected the photocatalytic activity and the optimal mole ratio of Ni(OH)2 in Ni(OH)2/TiO2 composite was determined to be 1.0%. The optimal rate of H2 evolution is about 15.76μmolh−1, which is about 90 times higher than pure TiO2 under the same condition. After 5h of irradiation, the photocatalytic activity of Ni(OH)2 as the cocatalyst for hydrogen evolution is much higher than other first-row transition metal based oxide/hydroxide materials, such as cobalt oxide (CoOx), cobalt hydroxide (Co(OH)2), nickel oxide (NiOx), ferric hydroxide (Fe(OH)3) and copper hydroxide (Cu(OH)2) on the surface of TiO2 semiconductor.