Enhanced Electrocatalytic Oxidation of Small Organic Molecules on Platinum-Gold Nanowires: Influence of the Surface Structure and Pt-Pt/Pt-Au Pair Site Density

Abstract

The electrochemical oxidation of small organic molecules (SOMs) such as methanol and glucose is a critical process and has relevant applications in fuel cells and sensors. A key challenge in SOM oxidation is the poisoning of the surface by carbon monoxide (CO) and other partially oxidized intermediates, which is attributed to the presence of Pt−Pt pair sites. A promising pathway for overcoming this challenge is to develop catalysts that selectively oxidize SOMs via "direct" pathways that do not form CO as a primary intermediate. In this report, we utilize an ambient, template-based approach to prepare PtAu alloy nanowires with tunable compositions. X-ray photoelectron spectroscopy measurements reveal that the surface composition matches that of the bulk composition after synthesis. Monte Carlo method simulations of the surface structure of PtAu alloys with varying coverage of oxygen adsorbates and varying degrees of oxygen adsorption strength reveal that oxygen adsorption under electrochemical conditions enriches the surface with Pt and a large fraction of Pt−Pt sites remain on the surface even with the Au content of up to 50%. Electrochemical properties and the catalytic performance measurements of the PtAu nanowires for the oxidation of methanol and glucose reveal that the mechanistic pathways that produce CO are suppressed by the addition of relatively small quantities of Au (∼10%), and CO formation can be completely suppressed by 50% Au. The suppression of CO formation with small quantities of Au suggests that the presence of Pt−Au pair sites may be more important in determining the mechanism of SOM oxidation rather than Pt−Pt pair site density.

Yttrium-based Double Perovskite Nanorods for Electrocatalysis

“…In principle, the electrooxidation of methanol can proceed through two possible pathways: (i) a direct pathway, wherein adsorbed methanol can be converted to either formaldehyde or formic acid, which is then subsequently transformed to CO 2 , and (ii) an indirect pathway, wherein the adsorbed organic species can be initially converted to adsorbed CO, which is then further oxidized to CO 2 . To evaluate which specific pathway the catalysts undergo during the MOR process, we performed formic acid oxidation reaction (FAOR) measurements, which are often used to determine whether methanol is preferentially oxidized via either the direct or indirect mechanism. , …”

“…46 To evaluate which specific pathway the catalysts undergo during the MOR process, we performed formic acid oxidation reaction (FAOR) measurements, which are often used to determine whether methanol is preferentially oxidized via either the direct or indirect mechanism. 47,48 Catalysts that pursue the indirect pathway in MOR will also tend to favor the creation of CO within FAOR. We note that the production of CO (and its subsequent oxidation to CO 2 ) requires a higher potential and yields a distinctive oxidation peak present at ∼0.9 V in the forward scan of FAOR.…”

Catalyst Electrodes with PtCu Nanowire Arrays In Situ Grown on Gas Diffusion Layers for Direct Formic Acid Fuel Cells

“…In addition to the control of composition, structure engineering has been another way to improve electrocatalytic performance. Among various structures, one-dimensional (1D) nanostructures, such as nanowires, nanorods, nanotubes, nanochains, etc., − have received increasing prominence in recent studies. Compared with nanoparticles, 1D nanostructures show good potential to alleviate the inherent drawback resulting from aggregation, dissolution, and Ostwald ripening .…”

Glucose Biosensors Based on Pinecone-Shaped Au and Ni Nanoparticle Composite Microelectrodes

“…To date, many noble metals, such as Au, Ag, Pt, Pd, and transition metals (Cu, Ni, Co), are often used as electrode surface modifiers due to the fact that they can improve the electrocatalytic ability of the electrochemical surface. Their bimetallic alloys (Pt−Au, 19 Co− Ni, 13 Cu−Pd 20 ) have better catalytic performance because of the synergistic effect between bimetals through an electronic and geometric effect. Among the above metals, gold nanoparticles (AuNPs) are commonly used to prepare electrochemical sensors because of their high stability, absorption, and chemical inertness, and good catalytic activity and electrical conductivity.…”

“…To date, many noble metals, such as Au, Ag, Pt, Pd, and transition metals (Cu, Ni, Co), are often used as electrode surface modifiers due to the fact that they can improve the electrocatalytic ability of the electrochemical surface. Their bimetallic alloys (Pt–Au, Co–Ni, Cu–Pd) have better catalytic performance because of the synergistic effect between bimetals through an electronic and geometric effect.…”