Freestanding monolayered nanoporous gold films with high electrocatalytic activity via interfacial self-assembly and overgrowth

Nanoporous gold freestanding films (NPG FSFs) have been fabricated via overgrowth of gold onto self-assembled monolayers of gold nanocrystals at planar fluid–fluid interfaces. The resulting NPG FSFs are ligand-free on their surfaces and their sizes can be as large as several cm2. The NPG FSFs are fairly mechanically robust; their effective Young's moduli are of the order of about 10 GPa. The NPG FSFs exhibit efficient electrocatalytic activity for methanol oxidation with an excellent electrochemical endurance, which is attributed to the presence of high-index facets on the curved surfaces of gold ligaments in the NPG FSFs. It is found that the catalytic performance of as-prepared NPG FSFs is related to the curved-to-flat surface area ratios of gold ligaments in NPG FSFs. The highly curved surface areas in the NPG FSFs can be increased via optimizing the concentration of HAuCl4 and the citrate to HAuCl4 molar ratio in the electroless plating solution.