Electrocatalytic Oxidation of Small Molecule Alcohols over Pt, Pd, and Au Catalysts: The Effect of Alcohol’s Hydrogen Bond Donation Ability and Molecular Structure Properties

Abstract

The direct alcohol fuel cell is a kind of power generation device that directly converts the chemical energy of small molecule alcohols into electric energy. In this paper, the electro-oxidation behaviors of some typical alcohols (methanol, ethanol, ethylene glycol, n-propanol, 2-propanol, and glycerol) over Pt, Pd, and Au electrodes were investigated in acidic, neutral, and alkaline media, respectively. By analyzing the activity information from a cyclic voltammetry (CV) method and some dynamic tests, several regularities were revealed in those electro-oxidation behaviors. Firstly, alkaline media is the best for the electro-oxidation of all these alcohols over Pt, Pd, and Au catalysts. Secondly, the hydrogen bond donation abilities (HBD) of different alcohols were found have a great relationship with the catalytic performance. In alkaline media, on Pt electrodes, the solute HBD is positively correlated with the ease of electrooxidation within the scope of this experiment. Contrarily, it is negatively correlated on Pd and Au electrodes. Additionally, for Pt catalysts in acidic and neutral media, the relationship becomes negative again as the HBD increases. Finally, the alcohol’s molecular structure properties were found to have a remarkably influence on the activity of different catalysts. Over the Pt electrode in alkaline media, the activation energy of methanol oxidation is 44.1 KJ/mol, and is obviously lower than the oxidation of other alcohols. Under similar conditions, the lowest activation energy was measured in the oxidation of n-propanol (14.4 KJ/mol) over the Pd electrode, and in the oxidation of glycerol (42.2 KJ/mol) over the Au electrode. Totally, among all these electrodes, Pt electrodes showed the best activities on the oxidation of C1 alcohol, Pd electrodes were more active on the oxidation of C2-3 monobasic alcohols, and Au electrodes were more active on the oxidation of polybasic alcohols.

Plasmonic Au–Pd Bimetallic Nanocatalysts for Hot-Carrier-Enhanced Photocatalytic and Electrochemical Ethanol Oxidation

“…Supplementary Figure S9 compares CVs in the dark immersed in 1 M KOH supporting electrolyte without 0.5 M EtOH. Peak anodic EOR current for the Au1-xPdx alloys increased from 1.51 mA cm −2 for Au, 9.26 mA cm −2 for Au0.9Pd0.1, 29.14 mA cm −2 for AuPd, and to 30.80 mA cm −2 for Pd, with current densities comparable or better than previous studies [48][49][50][51][52]. AuPd alloy exhibited similar electrochemical EOR activity as pure Pd despite 50% less Pd content.…”

“…Onset potentials during the anodic forward scan (i.e., left to right; VF and IF) were found to be reductively shifted from +0.72 V for Au to +0.30 V for Pd, listed in Table 3. Previous studies have reported ~1.25 to 5 mA/cm 2 for pure Au to Pd compositions, respectively [48,49]. Greater overpotential on Au is characteristic of EOR on Au compared with Pd for bulk metal surfaces [25,30,33].…”

Glycerol Electro-Oxidation in Alkaline Media and Alkaline Direct Glycerol Fuel Cells

“…Apart from the poor GOR activity at low potentials, gold presents some advantages over palladium or platinum, that is, it is more electrochemically stable in alkaline media, is more abundant and it has a lower price than the other precious metals [36]. Moreover, among Pt, Pd and Au electrodes, in alkaline media Au has the lowest activation energy for the electro-oxidation of glycerol [37]. Finally, Au has a very high degree of resistance to the formation of poisoning oxides such as CO [38].…”

Synthesis of Highly Active Pd@Cu–Pt/C Methanol Oxidation Electrocatalysts via Continuous, Co-Electroless Deposition

“…It is presumed that the shell contains Cu and Pt alone. Furthermore, of importance, palladium is known to be inactive for methanol electrooxidation under acidic conditions [ 26 , 27 , 28 , 29 ], ensuring that activity was only from the Pt–Cu shell and not the Pd core.…”