A method of forming a composite (e.g., a mixed electrode) by infiltration of a porous structure (e.g., one formed from an ionically conductive material) with a solution of a precursor (e.g., for an electronically conductive material) results in a particulate layer on and within the porous structure with a single infiltration. The method involves forming a solution comprising at least one metal salt and a surfactant; heating the solution to substantially evaporate solvent and form a concentrated salt and surfactant solution; infiltrating the concentrated solution into a porous structure to create a composite; and heating the composite to substantially decompose the salt and surfactant to oxide and/or metal particles. The result is a particulate layer on the pore walls of the porous structure. In some instances the particulate layer is a continuous network. Corresponding devices have improved properties and performance.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
 This invention was made with government support under Grant (Contract) No. DE-AC02-05CH11231 awarded by The United States Department of Energy. The government has certain rights to this invention.