Effects of Particle Surface Areas and Microstructures on Photocatalytic H2 and O2 Production over PbTiO3

The visible-light photocatalyst PbTiO3 was prepared in molten NaCl and PbO fluxes using 0.5:1-20:1 flux-to-reactant molar ratios by heating to 10001 degrees C 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 similar to 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 similar to 100 to 6000 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 PbTiO3 particles exhibit no well-controlled sizes or microstructures. The water-splitting photocatalytic activities of the PbTiO3 particles were evaluated in visible light (lambda > 420 nm), and yielded maximum rates of 27.4 mu mol.H-2.(g.h)(-1) for the PbTiO3 prepared using a 1:1 PbO molar ratio and 183 mu mol.H-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.