Abstract
In this experimental study, we investigate various transition-metal silicides as platinum-group-metal-(PGM)-free electrocatalysts for the hydrogen oxidation reaction (HOR), and for the hydrogen evolution reaction (HER) in acidic environment for the first time. Using cyclic voltammetry in 0.1 M HClO4, we first demonstrate that the tested materials exhibit sufficient stability against dissolution in the relevant potential window. Further, we determine the HOR and HER activities for Mo, W, Ta, Ni and Mo-Ni silicides in rotating disk electrode experiments. In conclusion, for the HOR only Ni2Si shows limited activity, and the HER activity of the investigated silicides is considerably lower compared to other PGM-free HER catalysts reported in the literature.
Highlights
The hydrogen oxidation/evolution reaction (HOR/hydrogen evolution reaction (HER)) is one of the most-studied reactions in aqueous and proton-exchange-membrane-(PEM)-relevant electrocatalysis, with platinum (Pt) exhibiting an exchange current density as high as ≈ 0.2 A/cm2metal [1]
We report the examination of transition metal silicides in terms of their been studied before for hydrogen oxidation reaction (HOR) or HER, while being promising in terms of stability against anodic electrochemical behavior in an acidic environment at inert atmosphere, and for the first time, dissolution [32]
With respect to the HER, we find minor activity on the minor or no HOR activity, probing the methanol oxidation reaction (MOR) or other anodic reactions investigated silicides compared to literature data available for other PGM-free materials
Summary
The hydrogen oxidation/evolution reaction (HOR/HER) is one of the most-studied reactions in aqueous and proton-exchange-membrane-(PEM)-relevant electrocatalysis, with platinum (Pt) exhibiting an exchange current density as high as ≈ 0.2 A/cm2metal [1]. With this high HOR activity, the Pt demand in typical PEM fuel cells (PEMFCs) is mainly dominated by the cathode electrode requirements rather than those of the anode, in order to minimize kinetic voltage penalties due to the orders of magnitude slower oxygen reduction reaction (ORR) [2]. As for the HOR in an acidic environment, the high HER activity of Pt has driven only little demand for the development of PGM-free HER electrocatalysts.
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