Ultralong durability of ethanol oxidation reaction via morphological design

A major challenge for the commercialization of direct alcohol fuel cells is the poor durability of the electrocatalysts. We demonstrate here that the morphological design of the catalyst could be an alternative solution. Sulfide-mediated Au@Pd nanowire arrays showed ultralong durability in chronoamperometric measurements, with 86% of the initial current retained after 1 h and an astonishing 38% retained after 56 h. The major discovery is that the turn-off voltage in the cyclic voltammetry could be delayed to as far as 5.2 V, suggesting delayed inhibition of the catalytic sites. The vertical arrays provide open diffusion channels with a concentration gradient so that the active sites would gradually move downward with the inhibition to form Pd-O-Pd. We postulate that the inhibition depends on the coupling between two Pd-OH groups, which is more probable at the Pd-O_x-rich regions of the top and less probable at the ethanol-rich regions at the bottom.