Glassy Metals as Electrocatalysts for Hydrogen Evolution and Oxidation: Part I : Electrocatalytic Properties of Amorphous Pt‐Si Alloy

The adsorption of hydrogen and the kinetics of the hydrogen evolution reaction (HER) on the vitreous alloy have been investigated. Five differently treated samples of the alloy have been studied and their electrocatalytic activities have been compared with those of pure polycrystalline Pt. The results show that the vitreous alloy is a single‐phase catalyst of uniform composition that is free from grain boundaries. The chemisorptive properties of Pt in the alloy change only slightly compared to Pt in the pure form; however, the silicon atoms in the alloy behave as weak electron donating ligands, filling in unoccupied d states of Pt. As a result, the free energy of hydrogen adsorption at the alloy decreases. In consequence, the rate of the HER is slower at the alloy than at the pure polycrystalline Pt surface. Annealing of the alloy in the presence of oxygen at temperatures above 400°C results in the formation of . The "spillover" of hydrogen from Pt into the silica has been observed at this sample. The hydrogen atoms deposited at Pt apparently migrate into the Consequently, the amount of hydrogen deposited in the UPD region of this electrode is many times higher than the value corresponding to the monolayer coverage.