Bromide-Regulated Anisotropic Growth of Desert-Rose-Like Nanostructured Gold onto Carbon Fiber Electrodes as Freestanding Electrocatalysts

Three-dimensional (3D) gas-diffusion electrodes (GDEs) as support for catalytic nanoparticles are important to the electrolysis and fuel cell fields to facilitate reactant transport and distribution and reach higher current densities. Hence, the assembly of nanostructured catalytic particles directly onto GDEs during the synthesis could be a powerful one-step strategy to target high performance and long-term durability thanks to the induced strong nanoparticle–support interaction. We report herein the use of bromide anions to shape the anisotropic growth of nanostructured desert-rose-like gold particles directly onto the GDE, as a freestanding GDE–Au catalyst for straightforward use in electrolysis without an additional step. We showed that the bromide ions determine the anisotropy of the particles, resulting in the growth of gold into nanoplates enclosed by (111) facets. The formation of hierarchical nanostructured three-dimensional (3D) Au at the GDE surface was explained by the nanoparticle-mediated aggregation mechanism and the preferential adsorption of Br– on the (111) facet, leaving behind dominant planar structured nuclei, which then self-assemble. Electrocatalytic tests toward the glycerol electro-oxidation demonstrated that the as-synthesized freestanding surfactant- and binder-free GDE–Au material (100 μgAu cm–2) delivered a high specific peak current density of jp = 33 mA cmAu–2, which is three and seven times higher than the tested commercial Au/C nanocatalyst at loadings of 76 and 152 μgAu cm–2, respectively. This study provides future directions for the synthesis and application of nanostructured catalysts for alcohol oxidation as an alternative to anodic oxygen evolution, which consumes the majority of the electricity input during the electrolysis.