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

摘要

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, N_2 adsorption measurement Brunauer, Emmet, Taller (BET) and Barrett-Joy ner— Halenda theory, UV-Vis 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. Fe_2O_3 is uniformly dispersed on the HMS surface; it works synergistically to make Fe-HMS photoelectrochemically active. The flat band potential (-0.75 V_Sce) is higher than the potential of hydrogen generation (-0.50 V_(SCe) at pH~7), and the material shows high efficiency for hydrogen evolution upon visible light. The photoactivity in Na_2SO_4 and Na_2SO_3 (0.1 M) solution was found to be 136 and 175 umolg~(-1) min~(-1), respectively under full light (29mWcm~(-2)). The tendency to saturation, observed only in SO_3~(-1) electrolyte, is ascribed to the competitive reduction of the end product, namely S_2O_6~(-2) with the water reduction.