Mesoporous Pt/TiO2-xNx nanoparticles with less than 10 nm and high specific surface area as visible light hydrogen evolution photocatalysts

Mesoporous TiO2-xNx nanoparticles were synthesized by selective dissolving of Si in N-doped Ti-Si binary oxides, which were nitridized at 900 °C in a flow of ammonia gas, and the mesoporous TiO2-xNx photocatalysts were then modified by depositing Pt through a microwave polyol method. The samples were characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), N2 adsorption–desorption, UV–vis spectroscopy and X-ray photoemission spectroscopy (XPS). The results indicated that the addition of SiO2 remarkably changed the phase composition, BET-specific surface area and the photocatalytic H2 production activity of TiO2-xNx nanoparticles. The incorporation of Si in Ti-Si binary oxides can suppress phase transformation of TiO2 from anatase to rutile and inhibit the TiO2 crystallite growth up to 900 °C. The BET surface area of the mesoporous TiO2-xNx nanoparticle was >138 m2 g−1 while with a crystallite size <10 nm, and the sample had a good visible light response. Photocatalytic hydrogen production results showed the N-doped Pt/TiO2 derived from Si: Ti = 1:1 of Ti-Si binary oxides exhibited the highest H2 evolution rate as high as 15.2 μmol g−1 h−1 under visible light irradiation, which is almost 10 times larger than commercial TiO2 nanoparticles P25. In addition, the co-catalyst optimized amount of Pt required for optimal photocatalytic H2 production activity was 2.0 wt%.