Hydrothermal Synthesis and Photocatalytic Properties of Catisio5 for Hydrogen Production

Titanite (CaTiSiO5) nanomaterials were synthesized by two hydrothermal methods and then calcined at 550 and 1000 °C, respectively. Their textural properties, crystalline structures, morphological features, and optical properties were characterized using N2 adsorption-desorption isotherms (BET), X-ray diffraction (XRD), transmission electron microscopy-energy dispersive spectroscopy (TEM-EDS), thermogravimetry-differential thermal analysis (TG-DTA), and UV-vis spectroscopy. The samples calcined at 550 °C mainly consisted of anatase TiO2 with some CaCO3 and amorphous SiO2, which converted into CaTiSiO5 with a small amount of CaSiO3 at 1000 °C. The band gap energy (Eg) was lower because of the CaTiSiO5 formation at higher calcination temperature. The CaTiSiO5 photoactivity was evaluated in water splitting under UV light irradiation for H2 production. The highest H2 production rate was obtained with the nanomaterials prepared by the Method II calcined at 1000 ºC. When formic acid was used as sacrificial agent, the hydrogen generation rate remarkably increased by 3 - 5 times (160 µmol·g-1·h-1). However, in the presence of methanol, the hydrogen generation rate was not significantly increased. Clearly, the acidic reaction media promoted the reduction of protons on the surface of the catalysts by trapping the excited electrons in the CaTiSiO5 conduction band, favouring the hydrogen production.