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Electrocatalysis of the HER in acid and alkaline media

Danilovic Nemanja (Materials Science Division, Argonne National Laboratory, Argonne, Illinois, USA)
Subbaraman Ram (Materials Science Division, Argonne National Laboratory, Argonne, Illinois, USA)
Strmcnik Dusan (Materials Science Division, Argonne National Laboratory, Argonne, Illinois, USA)
Stamenkovic Vojislav R. (Materials Science Division, Argonne National Laboratory, Argonne, Illinois, USA)
Markovic Nenad M. (Materials Science Division, Argonne National Laboratory, Argonne, Illinois, USA)

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

Keywords: volcano plot, HER, hydrogen evolution reaction, acid, alkaline