Intrinsic photocatalytic water reduction over PbGaBO4 comprising edge-sharing GaO6 chains

Abstract

Metal borates are well-known optical materials while their semiconducting behavior, i.e. photocatalytic property, was less studied. Inspired by the recent publications on gallium borates with good photocatalytic performances, we investigated photocatalytic water reduction activity of another gallium borate, PbGaBO4, comprising edge-sharing GaO6-chains. Both conventional and solution assisted solid state reaction methods were employed for the preparation. Phase purity and the crystallinity of both samples were identified by powder X-ray diffraction and scanning electron microscopy. The UV–Vis reflectance spectra suggested the wide bandgap characteristic (4.10 eV) and theoretical calculations pointed out that the 6s and 5p orbitals of Pb2+ contribute to both the bottom of CB and the top of VB. However the ionic bonding of PbO in PbGaBO4 led to a slight hydrolysis during the photocatalysis process, which can be suppressed by loading cocatalysts of Pt and RuOx. In addition, such a surficial modification significantly improved the photocatalytic water reduction ability, with an optimal H2 evolution rate of 41.9(9) μmol/h/g under UV-light irradiation.