Hollow AuAg Alloy Nanourchins: Twin Plane and Surface Treatment for Enhanced Methanol Electrooxidation Performance

Direct methanol fuel cells (DMFCs) have bright prospects because of their high energy density, simple structure, small fuel cartridge, instant recharging, and ease of storage and transport. Noble metals, which have long been considered the most effective catalyst for DMFCs, have also attracted great attention. Gold metal usually is inert in most electrocatalytic reactions. Here, we demonstrate the well-nanotextured urchinlike hollow Ag-doped Au particles show greatly enhanced electrocatalytic performance in the methanol oxidation reaction (MOR) system. The growth mechanism of these hollow AuAg nanourchins (NUs) in a simple seed-mediated synthesis route is investigated on the basis of theoretical calculation. We discovered that the surfactants, L-Dopa molecules, direct the anisotropic growth of Au nanocrystals which germinated from twin planes. Thus, plenty of spikelike tips are constructed on the hollow nanoparticles with densely distributed twin planes. A robust but simple surface treatment strategy is developed and investigated. After surface treatment, the surfactants on the AuAg NUs can be effectively removed in a short time, and large specific electroactive surface area and remarkable catalytic activities have been obtained. In the MOR system, hollow AuAg NUs have exhibited a 16.3 times higher mass activity and 2.3 times higher specific activity than the spherical Au nanoparticles with similar size. The excellent catalytic properties are contributed by the densely grown spines, twin plane structure, and trace amounts of Ag atoms. Especially, such densely distributed twin planes in the hollow and hierarchical noble metal catalysts have been scarcely investigated and reported. The results reveal that the hollow AuAg NUs are a promising electrocatalyst for methanol fuel cells, and these findings present huge opportunities for enhancing the catalytic activities by designing complex merits and surface treatment.