Surfactant-free fabrication of porous PdSn alloy networks by self-assembly as superior freestanding electrocatalysts for formic acid oxidation

Abstract

The fine design of three-dimensional (3D) nanocatalysts has attracted great research interest, particularly in fuel cells. In this paper, 3D porous PdSn alloy networks were successfully synthesized for the first time at 60 °C by a facile self-assembly method without using any surfactants. Through comprehensive physical characterization, the formation of a porous network structure with an average diameter of 7 nm was confirmed. The as-prepared PdSn alloy networks exhibited greatly enhanced catalytic performance towards formic acid oxidation (FAO) compared to Pd/C, which could be ascribed to their self-supported network nanostructure, the multifunctional effect between Pd and Sn and the particularly “clean” surface. Also, the widespread amorphous SnO₂ greatly enhanced the stability of the network catalysts. Among the three different atomic ratios of PdSn networks, the Pd₂Sn₁ sample exhibited the highest peak current density (1.35 A mg_pd⁻¹), which was 2.3-fold higher than that of Pd/C. After chronoamperometric testing for 3600 s, the Pd₂Sn₁ networks still showed the highest mass activity (0.16 A mg_pd⁻¹), which was 16-fold higher than that of Pd/C. Furthermore, the Pd₂Sn₁ catalyst displayed the best performance for FAO among all reported PdSn network catalysts. Therefore, after surface electron and geometry modification, the as-obtained PdSn alloy networks can be applied as state-of-the-art electrocatalysts for direct formic acid fuel cells.