Effects of Particle Surface Areas and Microstructures on Photocatalytic H_2 and O_2 Production over PbTiO_3

摘要

The visible-light photocatalyst PbTiO_3 was prepared in molten NaCl and PbO fluxes using 0.5:1-20:1 flux-to-reactant molar ratios by heating to 1000℃ for a duration of 1 h. Yellow-colored powders were obtained in high purity, as confirmed by powder X-ray diffraction and exhibited a bandgap size of ~ 2.75 eV as determined by UV-Vis diffuse reflectance measurements. Roughly spherical and cubic shaped particles with homogeneous microstructures were observed with sizes ranging from ~ 100 to 6 000 nm, and surface areas ranging from 0.56 to 2.63 m~2/g. The smallest particle-size distributions and highest surface areas were obtained for the 10:1 NaCl flux molar ratio. By comparison, solid-state preparations of PbTiO_3 particles exhibit no well-controlled sizes or microstructures. The water-splitting photocatalytic activities of the PbTiO_3 particles were evaluated in visible light (λ >420 nm), and yielded maximum rates of 27.4 μmol·H_2·(g·h)~(-1) for the PbTiO_3 prepared using a 1:1 PbO molar ratio and 183 μmol • O_2 • (g • h)~(-1) for the solid-state prepared sample. The rates were inversely correlated with the particle surface areas. The relationship between particle morphology and photocatalytic activity provides important insights into understanding the origins of photocatalysis in metal-oxides.