Heterostructured powders composed of microcrystalline (mc-) BaTiO3 and SrTiO3 cores coated with nanostructured (ns-) TiO2 shells were prepared using a sol-gel method. The influences of annealing temperature, coating thickness, cocatalyst loading, and core size on photocatalytic hydrogen production were experimentally determined. The amount of hydrogen produced depends on the annealing temperature, which influences the interface, phase composition, light absorption, crystallinity, mesoporosity, and surface area. The heterostructured powders produced more hydrogen than ns-TiO2 alone when annealed between 500 degrees C and 800 degrees C. The amount of hydrogen produced by heterostructures with 100-150 nm thick nanostructured titania coatings was greater than for thicker or thinner coatings. The optimum Pt loading was determined to be 1% by weight. Heterostructured powders consisting of mc-BaTiO3/ns-TiO2 produce more hydrogen than those with nano-sized BaTiO3 cores, suggesting a size effect that is counter to the conventional relationship between catalytic activity and particle size. Copyright (c) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.