Open-circuit Decay Method Research Articles

Combination rate of hydrogen atoms adsorbed on a polycrystalline platinum electrode at hydrogen underpotentials in sulphuric acid solution

Steady-state cathodic currents i c passing through a polycrystalline, smooth Pt electrode in 0.5 M H 2SO 4 were measured at constant potentials in the range from 0.45 to 0.05 V, at which the coverage by adsorbed hydrogen on the electrode surface is less than unity. It was found that current i c , which results from the combination of adsorbed hydrogen atoms, depends on both the adsorption state and the coverage on the electrode surface. The characteristic variation of i c with hydrogen coverage was explained in terms of the geometric arrangement of the adsorption sites. The combination rate constant and the mobility of the adsorbed hydrogen atoms estimated from the steady-state current measurement were in agreement with those obtained using the open-circuit decay method.