Electrocatalysis of the HER in acid and alkaline media

Abstract

Trends in the HER were studied on selected metals (M = Cu, Ag, Au, Pt, Ru, Ir and Ti) in acid and alkaline environments. It was found that with the exception of Pt, Ir and Au, due to high coverage by spectator species on nonnoble metal catalysts, the experimentally established positions of Cu, Ag, Ru and Ti in the observed volcano relations are still uncertain. It was also found that while the M-Hupd binding energy most likely controls the activity trends in acidic solutions, the trends in activity in alkaline solutions are controlled by a delicate balance between two descriptors: the M-Had interaction and the energetics required to dissociate water molecules. The importance of the second descriptor was confirmed by introducing bifunctional catalysts such as M modified by Ni(OH); e.g., while the latter serves to enhance the catalytic decomposition of water, the metal sites are required for collecting and recombining the produced hydrogen intermediates. Copyright 2013 (CC) SCS.