PNNL

Abstract

Finely structured, supported thin films offer a host of opportunities for fundamental and applied research. Nanostructured materials often exhibit physical properties which differ from their bulk counterparts due to the increased importance of the surface in determining the thermodynamics and behavior of the system. Thus, control of the characteristic size, porosity, morphology, and surface area presents opportunities to tailor new materials which are useful platforms for elucidating the fundamental processes related to energy conversion and storage.1-2 The ability to produce high purity materials with direct control of relevant film parameters such as porosity, film thickness, and film morphology is of immediate interest in the fields of electrochemistry, photocatalysis, and thermal catalysis.3-4 Studies of various photoactive materials have introduced questions concerning the effects of film architecture and surface structure on the performance of the materials,5 while recent work has demonstrated that nanostructured, mesoporous, or disordered materials often deform plastically,6 making them robust in applications where volumetric expansion and phase transformations occur, such as in materials for lithium-ion batteries.7-9 Moreover, renewed emphasis has been placed on the formation of semi-conductive electrodes with controlled pore-size and large surface areas for the study and application of pseudo-capacitance and cation insertion processes for electrical energy storage.4 Understanding how the performance of such materials depends on morphology, porosity, and surface structure and area requires a synthesis technique which provides for incremental variations in structure and facilitates assessment of the performance with the appropriate analytical tools, preferably those that provide both structural information and kinetic insight into photoelectrochemical processes.