Surface structure-sensitivity dependence and mechanistic study of the glucose electro-oxidation on Pt stepped surfaces in neutral solution (pH 7)

Abstract

The electro-oxidation of glucose (0.01 M) in a neutral solution phosphate buffer solution – pH ~7 (0.1 M) is strongly sensitive to the surface structure. On surfaces containing (100) terraces domains the reaction occurs mainly into these sites due to their higher activity. Higher (111) step density into (100) terrace domains conducts the reaction through a less poisoned and energetic pathway because steps inhibit the cyclic carbonate formation. On surfaces containing (111) terrace sites, on large atom-wide terrace (𝑛 ≥ 9) the reactivity of the (100) steps seems to be mainly associated to the anticipation of the formation of glucuronic acid and favor its oxidation to glucaric acid and/or xylonic acid + CO, that are more energetic reactions. On the other hand, when the step density is increased, the catalytic activity decreases as result of adsorption of intermediates and/products generated during the reaction on (100) steps. Lower and medium (110) density steps favor the adsorption of glucose on surfaces containing (111) terraces symmetry, but independently of the terrace step symmetry, as the (110) step density is increased the electrocatalytic activity is reduced because the reaction takes place through a more poisoned pathway, with the formation of a greater amount of species that adsorb strongly on the (110) sites and block the surface.