Photocatalytic Hydrogen Evolution from Earth Abundant Nickel Oxide Clusters Dispersed on MCM-48 Mesoporous Materials

NiO, as an earth abundant metal oxide that has been extensively studied as a co-catalyst for a variety of photocatalytic reactions, including solar hydrogen generation. Mesoporous materials have been used as a support to disperse spatially isolated semiconductor clusters to minimize photoinduced charge-carrier recombination and enhance photocatalytic efficiency. Such well-dispersed semiconductor particles encapsulated in mesoporous matrices possess small sizes due to quantization effect and higher redox potentials compared with those in bulk. In this work, NiO semiconductors were dispersed onto MCM-48 mesoporous materials and their photocatalytic activities were explored. The physico-chemical properties of all the prepared samples have been investigated using a wide selection of techniques ranging from powder X–ray diffraction (XRD), BET surface area analysis, atomic absorption spectroscopy (AAS), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectra (DRS), and X-ray photoelectron spectroscopy (XPS) and a structure-activity relationship was obtained. The MCM-48 supported NiO materials exhibit significantly enhanced activity and hydrogen evolution rate compared with bulk NiO. The use of MCM-48 cubic phased mesoporous materials facilitates the high dispersion of NiO species and is also conducive to restrain the size of NiO into small clusters. Meanwhile, the presence of both NiO and Ni₂O₃ species and the formation of the NiO/Ni₂O₃ heterojunction positive factors for the enhanced photocatalytic activity since the photogenerated charge-carrier can be effectively separated.