PtAg/MnOx/C as a promising electrocatalyst for glycerol electro-oxidation in alkaline medium

Abstract

This study shows the positive effect that Ag possesses on Pt in order to promote the glycerol electro-oxidation in alkaline medium and how this effect can be boosted with an appropriate catalyst support, such as MnOx/C. The addition of Ag to the catalyst formulation firstly impacts on the structural and electronic features of the bimetallic PtAg/C catalyst. The diffractograms evidence the formation of a PtAg nanometric alloy, which alters the electronic environment of Pt as evidenced by the reduction of the Pt LIII white line hump in the XANES spectrum. This effect is intensified at high potential in the PtAg/MnOx/C catalyst, indicative of the low affinity of Pt to form surface PtOx species, leading to a Pt surface in which the intermediates formed are less strongly adsorbed. Moreover, MnOx can act as a source of oxygenated species required by the glycerol electro-oxidation reaction (GEOR), leading to an optimum catalytic surface. Such combination of factors leads to a very electroactive material for glycerol electro-oxidation as demonstrated by the cyclic voltammetry, chronoamperometric curves and in the actual fuel cell, in addition to a different product distribution characterised by in-situ electrochemical Fourier transform infrared spectroscopy (EC-FTIR).