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

Abstract

• Glucose electro-oxidation in neutral solution is a sensitive-structure reaction. • On Pt-[( n )(1 1 1)x(1 0 0)]: when n ≥ 9 , [1 0 0] steps favor more energetic reactions pathways. • As higher the [1 0 0] steps density on (1 1 1) terraces, lower is the catalytic activity. • On narrow (1 0 0) terraces, [1 1 1] steps conduce the reaction through less poisoned path. • [1 1 0] steps sites favor the CO L adsorption, especially as narrower as the surface is. 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 (1 0 0) terraces domains the reaction occurs mainly into these sites due to their higher activity. Higher (1 1 1) step density into (1 0 0) terrace domains conducts the reaction through a less poisoned and energetic pathway because steps inhibit the cyclic carbonate formation. On surfaces containing (1 1 1) terrace sites, on large atom-wide terrace ( n ≥ 9 ) the reactivity of the (1 0 0) 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 (1 0 0) steps. Lower and medium (1 1 0) density steps favor the adsorption of glucose on surfaces containing (1 1 1) terraces symmetry, but independently of the terrace step symmetry, as the (1 1 0) 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 (1 1 0) sites and block the surface.