Electrooxidation of Organic Substances on Platinum Modified with Oxotungstate Adlayers

Abstract

The behavior of a platinized platinum electrode (roughness factor ∼500) in 0.5 M H₂SO₄ containing Na₃PW₁₂O₄₀ (PW₁₂) is studied by cyclic voltammetry. It is established that the effect of the PW₁₂ additive on the adsorption of hydrogen and oxygen is similar to the influence exerted by specifically adsorbed anions: a predominant displacement of strongly-bound hydrogen and a heavy suppression of oxygen adsorption are observed. It is shown that the regularities of oxidation of methanol, ethylene glycol, and formic acid at platinized platinum undergoe substantial alteration in the presence of PW₁₂. In the region of potentials E _r = 0.6–0.8 V, where the limiting stage of these processes is the adsorption of organic molecules, the oxidation rates substantially decrease. The run of steady-state polarization curves in the region E _r = 0.40–0.55 V depends on the direction of potential change and the extreme value of E _r. With E _r varied from 0.6–0.8 V in the direction of lower values in the interval E _r < 0.45–0.50 V, the oxidation processes accelerate as compared with the rates in the absence of PW₁₂. The acceleration occurs if conditions are created for a preliminary adsorption of the tungstate.