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

Abstract

Three-dimensional (3D) gas diffusion electrodes (GDEs) as support for catalytic nanoparticles are important to the electrolysis and fuel cells 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 nanoparticlesupport 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 a growth of gold into nanoplates enclosed by (111) facets. The formation of hierarchical nanostructured 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 towards the glycerol electrooxidation demonstrated that the as-synthesized freestanding surfactant-and binder-free GDE-Au material 2 (100 µgAu cm −2) delivered a high specific peak current density of jp = 33 mA cmAu −2 , which is 3 and 7 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.

Deciphering the Electrocatalytic Reactivity of Glucose Anomers at Bare Gold Electrocatalysts for Biomass-Fueled Electrosynthesis

“…Figures S22 and S23 demonstrate that the bromide anion triggers the predominance of (111). 28,30 The above results confirm our ability to synthesize bare (organic ligand-free) and free-standing GDE-Au electrocatalysts, which is important not only fundamentally to access intrinsic electrocatalytic activity but also to be implemented into real applications of electrolyzers. Indeed, electrocatalysts are currently premade as a powder or liquid sample before drop-casting onto conductive supports such as glassy carbon or metal foams.…”

“…The lead underpotential deposition (Pb UPD ) ,, experiments by cyclic voltammetry (CV) of Figure e,f validate the above results for both GDE-Au and bulk Au. Figures S22 and S23 demonstrate that the bromide anion triggers the predominance of (111). , …”

“…The profile of E (t) suggests that the relaxation is central to replenish the AuBr 4 – reagent in the vicinity of the electrode. Bromide regulates the nucleation and growth of Au seeds into particles , and is easily removed by washing with water. The reddish color in Figure b evidences the presence of gold.…”

“…Our choice of gold as the electrode material was guided by preliminary thermodynamic and kinetic tests (Figures S1−S2 − reagent in the vicinity of the electrode. Bromide regulates the nucleation and growth of Au seeds into particles 28,29 and is easily removed by washing with water. The reddish color in Figure 1b evidences the presence of gold.…”

Circumventing Challenges: Design of Anodic Electrocatalysts for Hybrid Water Electrolysis Systems

“…Reproduced with permission. [69] Copyright 2020, American Chemical Society. metals can further enhance the electrocatalytic performance and lower noble metal composition due to different mechanisms.…”