Troy Townsend's thesis explores the structure, energetics and activity of three inorganic nanocrystal phoatalysts. The goal of this work is to investigate the potential of metal oxide nanocrystals for application in phoatalytic water splitting, which could one day provide us with clean hydrogen fuel derived from water and solar energy. Specifically, Townsend's work addresses the effects of co-catalyst addition to niobium oxide nanotubes for phoatalytic water reduction to hydrogen, and the first use of iron oxide 'rust' in nanocrystal suspensions for oxygen production. In addition, Townsend studies a nickel/oxide-strontium titanate nanocomposite which can be described as one of only four nanoscale water splitting phoatalysts. He also examines the charge transport for this system. Overall, this collection of studies brings relevance to the design of inorganic nanomaterials for phoatalytic water splitting while introducing new directions for solar energy conversion.