Progress in achieving improved performance in the generation and utilization of hydrogen depends on our ability to identify materials with optimized electrical and (photo)- electrochemical performance. Given their high volume fraction of interfaces, high chemical stability and versatility (ionic, electronic, optical property control), nanocrystalline electroceramic materials are of growing interest for advanced energy conversion and storage technologies. As grain size decreases towards the Debye length and grain boundaries come in closer proximity, space charge properties begin to dominate, resulting in modified charge transport. Through systematic variation of grain boundary properties by heterogeneous indiffusion of cations, the electronic and ionic carrier profiles in the space charge region may be altered. The relationships between space charge potential and defect profiles in the space charge regions are quantitatively analyzed, and implications for nano-ionic materials in thin film solid oxide fuel cells are discussed. From the standpoint of photoelectrochemical water splitting for hydrogen generation, optimizing the band gap, band alignments, and transport properties while retaining stability has remained a challenging objective. Novel nanocrystalline composite structures are discussed which exhibit features amenable to optimization of required properties and electrical measurements to determine key transport properties of titanium dioxide nanopowder, a photoanode material are introduced.