Photo-induced hydrogen on iron hexagonal mesoporous silica (Fe-HMS) photo-catalyst

The iron hexagonal mesoporous silica (Fe-HMS)-n photocatalyst, where n is the molar ratio Si/Fe in the precursor gel (=50), has been successfully synthesized at an ambient temperature using hexadecylamine as template agent. The material was characterized by X-ray diffraction, N2 adsorption measurement Brunauer, Emmet, Taller (BET) and BarrettJoynerHalenda theory, UVVis spectroscopy, high-resolution transmission electron microscopy and electron spin resonance. The electrical conductivity follows an Arrhenius-type law with activation energy of 0.04?eV. Fe2O3 is uniformly dispersed on the HMS surface; it works synergistically to make Fe-HMS photoelectrochemically active. The flat band potential (-0.75?VSCE) is higher than the potential of hydrogen generation (-0.50?VSCE at pH 7), and the material shows high efficiency for hydrogen evolution upon visible light. The photoactivity in Na2SO4 and Na2SO3 (0.1?M) solution was found to be 136 and 175 mu mol?g-1?min-1, respectively under full light (29?mW?cm-2). The tendency to saturation, observed only in SO32- electrolyte, is ascribed to the competitive reduction of the end product, namely S2O62- with the water reduction. Copyright (C) 2011 John Wiley & Sons, Ltd.