Cations Enhance Hydride Transfer to Noncatalytic Metals in Concentrated Alkaline Electrolytes

Journal Article · Wed Oct 08 00:00:00 UTC 2025 · Journal of Physical Chemistry. C

DOI: https://doi.org/10.1021/acs.jpcc.5c05397 · OSTI ID:3008509

Moutarlier, Louka J. ^[1]; Cato, Benjamin ^[1]; Mezerkor, Casey S. ^[2]; Bazak, Jonathan David  ^[3]; Kempler, Paul A.  ^[1]

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1. Univ. of Oregon, Eugene, OR (United States)
2. Univ. of Oregon, Eugene, OR (United States); Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
3. Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)

Alkali metal cations are known to influence the kinetics of the hydrogen evolution reaction (HER), acting as either promoters or inhibitors to the rate-determining step depending on the metal surface, local pH, and cation concentration. Despite the importance of concentrated electrolytes for commercial electrochemical cells, the impact of cations on the HER in concentrated alkaline environments (>1 M) and in mixed cation systems remains poorly understood. Here, this study quantifies the HER kinetics at polycrystalline metal surfaces (Pt, Au, Cu, and Fe) and the equilibrium solvation environment in pure and mixed alkali metal hydroxide electrolytes at concentrations up to 3.0 M. Kinetic analyses of Au, Cu, and Fe revealed a positive cation-concentration-effect that was primarily driven by changes to the charge transfer coefficient. Multinuclear NMR spectroscopy examined the solvation of H₂O/OH^– species and the alkali cations as a function of (mixed) alkali cation concentration(s), and demonstrated rapid exchange between solvent, hydroxide, and solvated cations. Together, these findings support models where HER kinetics on noncatalytic metal surfaces in strongly alkaline conditions are primarily governed by the average polarization and polarizability of the metal/solution interface and that increasing cation activity continues to increase the transfer coefficient at metal-hydroxide concentrations up to 3.0 M. Electrolytes and additives which can outcompete weakly hydrated cations and disrupt the interfacial water structure are expected to suppress parasitic HER at electrodes for energy storage and electroplating.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division (MSE)
• Grant/Contract Number: AC05-76RL01830; SC0023435
• OSTI ID: 3008509
• Report Number(s): PNNL-SA--214834
• Journal Information: Journal of Physical Chemistry. C, Journal Name: Journal of Physical Chemistry. C Journal Issue: 42 Vol. 129; ISSN 1932-7455; ISSN 1932-7447
• Publisher: American Chemical SocietyCopyright Statement
• Country of Publication: United States
• Language: English