Wei Liu, Yang Qu, Wei Zhou, Zhiyu Ren, Baojiang Jiang, Guofeng Wang, Le Jiang, Fulong Yuan* and Honggang Fu1*

Mixed-phase MgTiO3/MgTi2O5 microspheres were prepared through a salicylic acid precursor method and further calcined in air. The microspheres were formed through coordination, polymerization, and aggregation processes. Salicylic acid acted as a ligand in coordinating with metal ions, in addition to acting as a structure-directing agent in the polymerization and aggregation of the titanate precursor microspheres via chemical bonds and electrostatic attraction. The mixed-phase MgTiO3/ MgTi2O5 microspheres prepared by this method showed excellent photocatalytic hydrogen production efficiencies that were two and four times higher than mixed-phase nanoparticles and pure-phase nanoparticles, respectively, owing to their closed phase junctions and sphere-like morphologies. This versatile and facile salicylic acid precursor method was also used to prepare a number of other bivalent metal-based titanate microspheres, including BaTiO3, ZnTiO3, CoTiO3, NiTiO3, and CdTiO3.

Photocatalysis The photocatalytic hydrogen production experiments were conducted in an online photocatalytic hydrogen production system (AuLight, Beijing, CEL-SPH2N) at ambient temperature (20°C). The catalyst (0.1 g) was suspended in a mixture of distilled water (80 mL) and methanol (20 mL) in the reaction cell using a magnetic stirrer. Pt-loaded photocatalysts (1 wt.%) were prepared by a known standard in-situ photodeposition method using H2PtCl6 aqueous solution. Prior to the reaction, the mixture was deaerated by evacuation to remove the O2 and CO2 dissolved in water. The reaction was carried out by irradiating the mixture with UV light from a 300 W Xe lamp (AuLight, CEL-HXF300) with a UVREF filter (AuLight, 200–400 nm). Gas evolution was observed only under photoirradiation and the evolved gases were analyzed using an online gas chromatograph (SP7800, TCD, molecular sieve 5 Å, N2 carrier, Beijing Keruida Limited). The apparent quantum efficiency (AQE) for hydrogen generation was determined using the same closed circulating system with a 300 W Xe lamp and band pass filter (313 nm) illumination system. The light intensity was measured using a Si photodiode (Oreal 91105V). The total light intensity was 11.3 mW s−1 at 313 nm and the irradiation area was around 7 cm2 . The AQE values at different wavelengths were calculated using the following equation [23]: