Electrocatalytic Study of Ethylene Glycol Oxidation on Pt₃Sn Alloy Nanoparticles

Abstract

Ethylene glycol is a potential feedstock for direct alcohol fuel cells (DAFCs). The electro‐oxidation of ethylene glycol is, however, challenged by poor selectivity toward the complete‐oxidation product, CO2. Herein, we report an electrocatalytic study of ethylene glycol oxidation on monodisperse and homogeneous Pt3Sn alloy nanoparticles. The catalytic activity and selectivity toward CO2 are evaluated under potentiostatic conditions by using gas chromatography‐mass spectrometry. A comparative study is performed on the alloy catalyst with surface tin (oxide) species removed through an alkaline treatment. By comparing the electrocatalytic performances of the pristine and treated Pt3Sn catalysts, as well as commercial Pt/C, we are able to reveal the distinct roles of surface tin oxide and subsurface metallic tin species in the bimetallic electrocatalyst for complete oxidation of ethylene glycol: the former enhances the cleavage of C−C bond and the latter facilitates oxidative removal of the *CO intermediate.

Effect of Anode Material on Electrochemical Oxidation of Low Molecular Weight Alcohols—A Review

“…The complete oxidation of one molecule of ethylene glycol to carbon dioxide results in a gain of 10 electrons (in comparison, complete MOR results in a gain of 6 electrons, and EOR results in a gain of 12 electrons) [ 91 ].…”

“…Free OH − ions in the feed stream can be adsorbed on the surface of the electrodes [ 86 ]. Since hydroxide ions are present in the solution, they do not need to be produced in situ by water activation in the same amount as that in the acidic environment, which simplifies the overall process [ 86 , 91 , 162 ].…”

“…In the non-poisonous pathway, the main product of EGOR is oxalate, while for the poisonous one, products are formed during further oxidation of initially obtained formates [ 25 , 154 ]. Only some ethylene glycol molecules are fully oxidized, so the EGOR leads to a large number of intermediates containing two carbon atoms—C 2 intermediates—including glycolic acid, glyoxal, glyoxylic acid, oxalic acid, glycolaldehyde and glyoxal [ 88 , 91 , 161 , 162 , 163 , 165 ] ( Figure 6 ). The scheme of EG oxidation to C 2 intermediates can be written as shown in Figure 6 [ 162 ].…”

“…This step is common for both the poisonous and nonpoisonous paths [ 154 , 161 , 162 , 163 ]. The second step of the EGOR is the oxidation of the formulated intermediates [ 25 , 154 , 161 , 162 , 163 ], and because they are less prone to oxidation than the original compound, this is the rate-determining step for the whole oxidation reaction [ 91 , 154 , 161 , 163 ]. At room temperature, the yield of ethylene glycol oxidation to CO 2 does not exceed several percent, which makes it negligible [ 91 ].…”

“…Most of the established technologies for DAFCs are based on anodes made of platinum and its alloys [ 31 , 85 , 91 , 108 , 144 , 163 , 167 , 168 , 169 , 170 , 171 ]. Because of their popularity, their manufacturing process is well established, and the control of the metal ratio, alloy level and surface morphology is possible [ 115 , 162 ].…”