Fabrication of Self-Standing Porous Foam-like PdM (M = Ni, Fe, Co) Nanocrystals for Boosted Ethanol Oxidation Electrocatalysis

Abstract

Rational designing of self-standing porous foam-like PdM (M = Ni, Fe and Co) nanocrystals was achieved by a fast aqueous-solution method via the co-reduction of metal precursors using sodium borohydride. This was based on the crystallites’ coalescence growth mechanism, including quick nucleation of Pd that served as starting seeds for the nucleation of M, which attached directly along the specific crystallographic and lowered its high surface energy by diffusion of PdM atoms across the interface via Brownian motion to afford self-standing porous foam-like PdM nanocrystals. Amongst the as-prepared PdM nanocrystals, PdNi nanocrystals showed a superior alkaline ethanol oxidation reaction (EOR) activity and stability compared to PdFe, PdCo, Pd nanospheres (Pd-NSs) and commercial Pd/C (10 wt.%) catalysts. The EOR mass activity of PdNi was 1.32, 1.51, 2.01 and 24.05 times than those of PdFe, PdCo, Pd-NSs and Pd/C, respectively based on equal Pd mass. This was attributed to the lower synergistic effect in PdNi, which enhanced H2O activation/dissociation to give OH- species needed for rapid EOR kinetics, meanwhile, the porous foam-like morphology improved electron mobility and increased accessible active sites. This study revealed that low synergism in porous PdM nanocrystals is beneficial for enhancing the EOR activity and durability, which may allow the design of other binary Pd-based alloys for various electrocatalytic reactions.