Harnessing Electrolyte Chemistry to Advance Oxygen Reduction Catalysis for Fuel Cells and Electrosynthesis

Oxygen reduction reaction (ORR) is ubiquitous in many important energy conversion technologies, encompassing fuel cells, metal-air batteries, and H₂O₂ electrosynthesis. However, its inherently sluggish kinetics often leads to substantial overpotentials and losses in efficiency, thus prompting extensive efforts into catalyst optimization. In the past few years, growing research has underscored the pivotal role of electrolyte-associated factors in affecting the ORR performance. In this review, we focus on the intricate interplay between electrolyte properties, pH, cations, anions, and additives, and their impacts on ORR electrocatalysis, particularly for platinum (and its alloys) and nonprecious metal–nitrogen–carbon catalysts. We examine how these electrolyte-mediated alterations affect the electrode surface, reactive species, and microenvironment, thereby modulating the adsorption energetics of intermediates, catalyst stability and mass transport, and ultimately affecting the overall ORR process. We highlight the need for dynamic models and advanced probing technologies at the electrocatalytic interfaces, and advocate for adopting a holistic approach that synchronizes effects of electrolytes and catalysts in optimizing ORR electrocatalysis. This review lays the foundation for refining descriptive formulations for ORR electrocatalysis, which potentially guides the development of enhanced ORR cathodes for practical applications.