The role of chemisorbed hydroxyl species in alkaline electrocatalysis of glycerol on gold

Abstract

The mechanism of energy conversion in a direct glycerol fuel cell (DGFC) is governed by the anode supported heterogeneous steps of glycerol electro-oxidation. In aerated alkaline electrolytes, glycerol also participates in a base catalyzed process, which can release certain species mixing with the anode catalyzed surface products. As a result, selective probing of the surface catalytic reactions involving such systems can be difficult. The present work addresses this issue for a gold anode by using the analytical capability of cyclic voltammetry (CV). In addition, surface plasmon resonance measurements are used to optically probe the adsorption characteristics of the electrolyte species. The net exchange current of the oxidation process and the transfer coefficient of the rate determining step are evaluated by analyzing the CV data. The interfacial reactions and their products on Au are identified by measuring the number of electrons released during the electro-oxidation of glycerol. The results indicate that these reactions are facilitated by the surface bound hydroxyl species on Au (chemisorbed OH(-) and faradaically formed Au-OH). By comparing the findings for stationary and rotating electrodes, it is shown that, convective mass transport is critical to maintaining efficient progression of the consecutive oxidation steps of glycerol. In the absence of hydrodynamic support, the main surface products of glycerol oxidation appear to be glyceraldehyde, glycerate and malonate, formed through a net six-electron route. In the presence of controlled convection, a ten-electron process is activated, where mesaxolate is the likely additional product.

A Practical Approach in Glycerol Oxidation for the Development of A Glycerol Fuel Cell

“…The second peak corresponds to the glycerol oxidation which is presented in the literature by different authors [14][15][16][17][18][19][20][21][22]. In general, the catalytic activity for glycerol oxidation is observed with Pt, Cu, and Au electrodes.…”

“…in the study of Ureta [18], the mechanism of alcohol oxidation in alkaline media on a gold electrode was investigated and it is suggested that the optimal oxidation for alcohols is at pH 11. Also, Shi [19] studied the kinetics of low concentration of glycerol in alkaline media using voltammetry on a gold foil. Recently, Qi [20] studied the generation of tartronade during glycerol oxidation in alkaline media, using an AuC coated electrode.…”

On the Mechanistic Origins of the pH-Dependency in Au-Catalyzed Glycerol Electro-Oxidation: Insight from First Principles Calculations

“…For instance, neither the OH − ion (proton acceptor) coverage nor its role on EOG mechanism or kinetics under different electrochemical conditions have been explored in atomic detail. Partly controversial results regarding the mechanism have been published and it has remained unresolved whether Au(OH) ads catalyzes the dissociation of a C-H bond 48,49 or an O-H bond 2,18,19,24 and whether primary or secondary O-H/C-H bonds are more reactive on the Au surface. 22,50 It has also remained unresolved if chemical steps, such as keto-enol tautomerism between DHA and GLD identified for thermochemical glycerol oxidation, 51,52 are important in EOG and whether this depends on the pH.…”

Energy Storage Technologies for Off-grid Houses

“…The first peak corresponds to a typical sudden increase in Energy Storage Technologies for off-grid Houses 71 | B a c k u p 3 oxidation upon reducing gold from its oxidized state in alkaline media. The second peak corresponds to the glycerol oxidation which is presented in the literature by different authors [96][97][98][99][100][101][102][103][104].…”

“…in the study of Ureta [100], the mechanism of alcohol oxidation in alkaline media on a gold electrode was investigated and it is suggested that the optimal oxidation for alcohols is at pH 11. Also, Shi [101] studied the kinetics of low concentration of glycerol in alkaline media using voltammetry on a gold foil. Recently, Qi [102] studied the generation of tartronade during glycerol oxidation in alkaline media, using an AuC coated electrode.…”