Vertically Aligned and Surface Roughed Pt Nanostructured Wire Array as High Performance Electrocatalysts for Methanol Oxidation

Abstract

In this research, an enhanced electrocatalyst based on vertically aligned and surface roughened Pt nanostructured wire arrays (Pt NWAs) has been developed. Our results showed that Pt NWAs possessed extremely high electrochemical performance and efficiency toward methanol oxidation. The three-dimensional nanostructured wire array electrode was prepared with electrodeposition method using anodic aluminum oxide (AAO) membrane on silver substrate, after which the active array electrode was obtained by dissolving the AAO templates. Varying the electrodeposition current density and synthesis time led to the controlled length and surface roughness of the Pt nanostructured wires. Scanning electron microcopy, energy dispersive X-ray spectroscopy, and X-ray powder diffraction were employed to characterize the morphology, composition, and crystal structure of the nanostructured wires. Cyclic voltammetry (CV) and chronoamperometry were used to analyze the performance and endurance of the wire array electrode. Electrochemical impedance spectroscopy measurements provided insights in the electron transfer resistance between the electrode and analyte. Gas chromatography (GC) and UV−vis spectroscopy were carried out to identify the presence of the possible products and the relative concentration change of methanol vs the numbers of cyclic voltammetry scanning. The electrochemical measurements showed only one dominant forward anodic peak and the absence of backward anodic peak. GC results showed that methanol concentration decreased linearly with the CV scanning cycles, and a negligible amount of side products were detected, suggesting a complete methanol oxidation. This prepared electrode exhibited high electrochemical activity, high endurance, and low electron transfer resistance.

Two-Step Dry Synthesis of Binderless 3D Low Pt-Loading Electrocatalysts for Direct Alkaline Methanol Fuel Cell Anodes

“…The strong capillary forces acting during the evaporation of the electrolyte from the interstices of the nanotubes during the sample drying and the strong van der Waals interactions between nanotubes due to their alignment and narrow spacing induced bending and reassembled them in a cellular- or foam-like structure seen in Figure . This rearrangement of the MWCNTs has been observed in other studies. , To test if the MWCNT rearrangement is the result of electrolyte evaporation, the CA-tested samples were immediately freeze-dried after taking them out of the electrolyte to reduce the evaporation time. As can be seen in Figure S6c, in this case, no foam-like structures were observed, evidencing that the evaporation of the electrolyte indeed caused the rearrangement of the MWCNTs on some of the Pt/MWCNT/SS surfaces …”

“…This rearrangement of the MWCNTs has been observed in other studies. 47,48 To test if the MWCNT rearrangement is the result of electrolyte evaporation, the CA-tested samples were immediately freeze-dried after taking them out of the electrolyte to reduce the evaporation time. As can be seen in Figure S6c, in this case, no foam-like structures were observed, evidencing that the evaporation of the electrolyte indeed caused the rearrangement of the MWCNTs on some of the Pt/MWCNT/SS surfaces.…”

Platinum‐Based Electrocatalysts for Direct Alcohol Fuel Cells: Enhanced Performances toward Alcohol Oxidation Reactions

“…[65] Furthermore, it was established that a rough surface of catalysts can provide abundant of unsaturated atomic steps, edges, kinks and therefore are more active than that of the catalysts formed by flat surface. [90][91] Pt-based electrocatalysts with dendritic or porous geometrical configuration were therefore designed and prepared. [18,[92][93] Additionally, the hollow metal nanocrystals are also of great importance and interest, because they cannot only remarkably reduce the Pt usage, but also offer much larger specific surface area.…”

“…However, we should point out that recent investigations also illustrated that low‐index facets are better additional stability and improving activity [65] . Furthermore, it was established that a rough surface of catalysts can provide abundant of unsaturated atomic steps, edges, kinks and therefore are more active than that of the catalysts formed by flat surface [90–91] . Pt‐based electrocatalysts with dendritic or porous geometrical configuration were therefore designed and prepared [18,92–93] .…”

Direct Synthesis of Ultrathin Pt Nanowire Arrays as Catalysts for Methanol Oxidation

“…The addition of insulating binders like Nafion would further compromise the conductivity. [ 13 ] The packing of nanowires and polymers would also reduce the electrochemically active surface areas [ 13,14 ] and block diffusion paths. Hence, exploring new design of Pt electrocatalysts would be highly desirable but remains a significant challenge.…”