Enhanced Electrocatalytic Activities toward the Ethanol Oxidation of Nanoporous Gold Prepared via Solid-Phase Reaction

Abstract

The rational design of highly active electrocatalysts for the ethanol electrooxidation reaction (EOR) is important for future commercial applications of efficient direct ethanol fuel cells. Herein, we describe application of a solid-phase reaction for the creation of a well-defined, high-efficiency, nanoporous gold (NPG) electrocatalyst for EOR. The evaluation of the feature size and physical properties of the NPG electrocatalysts was undertaken using field-emission scanning electron microscopy and high-resolution transmission electron microscopy. Additionally, the catalytic performance of the prepared NPG electrocatalysts was determined using cyclic voltammetry (CV) and chronoamperometry (CA), with results indicating that their enhanced electrocatalytic activities and long-term durability were highly dependent upon morphology. The created NPG exhibited a mass activity of 308 mA mgAu –1 toward EOR in alkaline media, which is much higher than those of nanostructured Au catalysts. In particular, 800-cycle CV and 2000-s CA tests in alkaline solution consistently suggested excellent long-term stability and durability of the NPG. Our findings suggest the developed NPG as a promising electrocatalyst and an ideal substrate for multifunctional electrocatalysts for EOR.

Cryoaerogels and Cryohydrogels as Efficient Electrocatalysts

“… where is the total charge necessary for the metal oxide reduction, v is the scan rate (0.05 V s −1 ), and m is metal loading (g) on the electrode. Q is the conversion factor, commonly taken as 0.386 mC cm −2 for gold, [ 27 ] 0.420 mC cm −2 for platinum, [ 28 ] and 0.405 mC cm −2 for palladium. [ 29 ] The calculated ECSAs for all noble metal coatings are displayed in Figure 3d.…”

“…The increase of catalytic activity by higher accessible surface areas was already confirmed in literature. [ 14,27,33,34 ]…”

“…Dendritic gold nanostructures for example showed an activity of 137 mA mg −1 in EOR, whereas polycrystal‐gold showed 22 mA mg −1 . [ 27 ] In the case of platinum, hollow nanosphere materials showed a comparable activity of 1000 mA mg −1 . Also, the ECSA‐normalized activity was of similar extent (48 mA cm −2 ).…”

“…The increase of catalytic activity by higher accessible surface areas was already confirmed in literature. [14,27,33,34] Further, a shift in the oxidation peak potential can be recognized in the forward scan for cryoaerogels frozen with isopentane (Figure 4). This overpotential can be explained by the diffusion controlled transport of ethanol species to the electrodes' active sites.…”

Nanoporous Gold for Energy Applications

“…Recently, Zhang et al. reported EOR on NPG with a dendritic‐like architecture with irregularly shaped Au‐nanobranches [32] . Their NPG structures were prepared not by the usual dealloying of AuAg alloy films, but by so called metal‐induced crystallization (MIC).…”