Recent Progress in Ruthenium-Based Electrocatalysts for Water Oxidation under Acidic Condition

Proton exchange membrane water electrolysis (PEMWE) is considered the most compatible technology with intermittent renewable energies for clean hydrogen generation. More than that, compared with alkaline electrolyzers, the totality of the practicality enhances due to the obvious advantages such as electrolysis efficiency, high hydrogen purity, low operation pressure, etc. However, the sluggish four-electron-transfer reaction of the oxygen evolution reaction (OER), which involves complex intermediates and multiple reaction steps, significantly impacts the overall electrolysis efficiency of PEMWE. Therefore, developing highly efficient, stable, and low-cost high-tech electrocatalysts for acidic OER is crucial. In comparison to expensive commercial iridium or iridium oxide electrocatalyst, Ru or Ru oxides are much cheaper alternatives that demonstrate superior catalytic performance for acidic OER. In this perspective, the generally accepted OER mechanisms including AEM and LOM are introduced with corresponding reaction pathways. Then, Ru-based electrocatalysts are explicated on performances and mechanisms for acidic OER, which include Ru metal and Ru metal-based alloys, RuO2-based catalysts, Ru oxide solid solutions, perovskites, pyrochlores, single atoms, and other Ru-based catalysts. Finally, the challenges and future research perspectives of Ru-based catalysts for acidic OER are discussed.