(521ay) Understanding the Acid Electrolyte Anion Adsorption Effects for Oxygen Electrocatalysis

The surface-electrolyte microenvironment plays an important role in the performance of renewable electrochemical energy technologies such as fuel cells, electrolyzers, and batteries. Polymer electrolyte membrane (PEM) fuels cells and electrolyzers have the advantage of operation at higher current densities and having higher stability toward load cycling and shutdowns compared to alkaline fuel cells and electrolyzers. Focusing on the oxygen-based (oxygen reduction reaction-ORR and oxygen evolution reaction-OER) electrochemical reactions, which typically hamper the efficiency of fuel cells and electrolyzers,^1,2 respectively, due to the sluggish kinetics, a fundamental understanding of acid electrolyte anion effects at or near the electrocatalytic surface may engineer better electrode- electrolyte interfaces with tuned local surface-electrolyte microenvironments and help facilitate the design of non-noble electrocatalytic materials.

Previous theoretical and experimental work has been focused on studying anion effects in acidic media using Pt electrocatalysts and changes in performance as a function of anion species have been generally attributed to competitive adsorption. Anion effects on other catalytic materials have not been investigated in detail. Therefore, to better understand acid electrolyte anion effects on the ORR and OER activity of both strong and weak oxygen-binding metals and metal oxides, we consider Pt³, Pd⁴, Ag, and IrO₂. We evaluated various electrolytes (HClO₄, HNO₃, H₂SO₄, H₃PO₄, HF, HCl, HBr, and HI) interaction in the electrochemical double-layer microenvironment and how these anions modify the adsorption energies of the ORR and OER reaction intermediates. These insights provide guidance on opportunities to improve performance for ORR and OER catalysts and related electrochemical energy technologies.

1 Shih, A. J. et al. Nat Rev Methods Primers 2, 1–19 (2022)

2 Gunasooriya, G. T. K. K. et al. ACS Energy Lett. 5, 3778–3787 (2020)

3 Kamat, G. A. et al. Commun Chem 5, 1–10 (2022)

4 Zamora Zeledón, J. A. et al. ChemElectroChem 8, 2467–2478 (2021)