Hydrogen Evolution Reaction in Alkaline Solution: Catalytic Influence of Pt Supported on Graphite vs. Pt Inclusions in Graphite

Graphite powders with supported Pt 5 and 20 weight percent (w/o) Pt and Pt inclusions (13 and 17 w/o) in graphite have been bonded with an inorganic polymer and used as cathodes for the hydrogen evolution reaction (HER) in 1 M KOH solution. Pt‐supported electrodes are more active than the electrodes containing Pt inclusions in graphite . However, in high‐current‐density conditions (0.25 A/cm2), is stable while disintegrates after 24 h. The ac impedance diagrams display two semicircles on the complex‐plane plot for both and electrodes but only one for pure graphite. The same equivalent circuit with two constant‐phase elements has been used to explain the behavior of these electrodes. For both materials, the HER proceeds via the Volmer‐Heyrovský mechanism. The difference in the electroactivity of these two materials is related to the effective amount of Pt available.