Palladium-decorated hierarchical titania constructed from the metal-organic frameworks NH<inf>2</inf>-MIL-125(Ti) as a robust photocatalyst for hydrogen evolution

Abstract

Engineering metal-organic frameworks (MOFs) into hierarchical structured materials is crucial for providing a viable platform to construct efficient catalysts and broaden their applications in energy conversion and photocatalysis. Here, a simple and efficient solid-state pyrolysis of Ti-MOFs (NH2-MIL-125) sacrificial template combined with a photo-reduction process was developed to construct a series of hierarchical TiO2 decorated with Pd nanoparticles. The hierarchical TiO2 inherited the well-defined rounded rectangular submicron-tablet from NH2-MIL-125 precursor and was constituted of uniform anatase TiO2 nanoparticles with an average size of 12 nm. Furthermore, the photocatalytic activity for the hydrogen production from water-methanol solution was improved by the optimization of the content of Pd as a cocatalyst, and the maximum was achieved with a Pd loading of 1.5%. The rate of H2 evolution of 1.5% Pd decorated hierarchical TiO2 (1.5% Pd/TiO2) reached to 979.7 μmol h−1 and 112.7 μmol h−1, under UV–vis light and simulated solar light, respectively. This unusual photocatalytic activity may be resulted from the positive synergetic effect of efficient light absorption, promoted separation and migration of photo-induced electron-hole carriers. The work highlights the potential of the MOFs-based hierarchical TiO2 in the photocatalytic water splitting under solar light.