Monolithic Au Nanoscale Films with Tunable NanoporosityPrepared via Dynamic Soft Templating for Electrocatalytic Oxidationof Methanol

We report the bottom-up synthesis of nanoporous gold (Au) thin films with monolithic morphology based on Au electrodeposition from a bicontinuous microemulsion (BME) as a dynamic soft template. Au electrodeposition occurs only at the aqueous phase of the BME, which has intertwined three-dimensional networks composed of aqueous and oil phases compartmentalized by surfactant and cosurfactant. Mutual progress in electrodeposition and dynamic change in the BME microstructure resulted in a monolithic Au nanostructure grown vertically to the electrode surface. The resultant film nanostructure can be widely and repeatably controlled by adjusting the initial BME composition and electrodeposition kinetic parameters, such as deposition potential and time. The resultant monolithic nanoporous Au film exhibited a significant decrease in the overpotentials of both methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) derived from its nanostructure, which could provide not only a large electrochemically active surface area but also abundant step/kink sites or preferably exposed facets.