(532bz) Exploring the Impact of Ionomer Composition and Loading on the Activity of Nonprecious Hydrogen Evolving Electrocatalysts

Hydrogen is an important commodity chemical, and it is being considered as a future fuel owing to its high gravimetric energy density (120 kJ/g).¹ Solar-driven water electrolysis, using photovoltaic cells linked to alkaline anion exchange membrane (AEM) electrolyzers, is an attractive approach for carbon neutral hydrogen production. In an effort to advance this green hydrogen technology, our research group is working to understand the activity of nonprecious metal catalysts for the alkaline hydrogen evolution reaction (HER).²

This presentation will focus on work to understand the impact of ionomer composition and loading on the performance of Ni-based alkaline HER catalysts. In analytical experiments using the rotating disk electrode (RDE) configuration, carbon-supported Ni–Mo composites yielded mass specific HER activities up to 200 mA/mg_cat at 100 mV overpotential and metal loadings of 0.25 mg_cat/cm² when using Nafion cation exchange ionomer in the catalyst ink preparation. However, this activity decreased to 50 mA/mg_cat when using a commercial poly aryl piperidinium (PAP) anion exchange ionomer. Control studies performed using Ni and Pt catalysts showed the opposite trend—catalysts films with PAP ionomer performed better than those using Nafion—which suggests interactions between the alkaline ionomer and Mo species are responsible for catalyst deactivation. Nonetheless, full AEM electrolyzer assemblies using Ni–Mo/C cathodes required <100 mV greater overpotential than those with Pt–Ru/C cathodes over the range from 0.1–2 A/cm² in current density. Results of further ongoing experiments directed at testing hypotheses regarding the impact of Mo on catalyst-ionomer interactions will also be discussed.

References

1. K. T. Møller, T. R. Jensen, E. Akiba and H. Li, Progress in Natural Science: Materials International, 2017, 27, 34–40.

2. Rituja B. Patil, Stephen D. House, Lance Kavalsky, Keda Hu, Shirley Zhong, Dilip Krishnamurthy, Manjodh Kaur, Venkat Viswanathan, Judith Yang, Yushan Yan, Judith Lattimer, and James R. McKone, manuscript under preparation.