Toward the fast and durable alkaline hydrogen oxidation reaction on ruthenium

Abstract

Anion exchange membrane fuel cells (AEMFCs) are becoming highly attractive for the efficient utilization of hydrogen energy due to the rapid development of platinum group metal (PGM)-free electrocatalysts for the cathodic oxygen reduction reaction. However, the kinetics of the anodic hydrogen oxidation reaction (HOR) in alkaline media is much more sluggish than the case in acid media. Ruthenium (Ru) possesses reasonable hydrogen binding energy and oxyphilic ability to reach balanced adsorption of OH_ad and H_ad at low anode potentials, and, to a certain degree, Ru-based electrocatalysts are considered as potential alternatives to Pt toward the alkaline HOR. Although a number of reviews have overviewed the development of alkaline HOR electrocatalysts from different viewpoints, a systematic review on Ru-based alkaline HOR electrocatalysts is still rare. In this review, we summarize the recent advances in Ru-based electrocatalysts for the alkaline HOR. The fundamental reaction mechanisms of the electrocatalytic HOR under alkaline conditions are introduced and discussed. Then, the recent advances in Ru-based electrocatalysts are summarized on the basis of four catalyst-design strategies including the composition effect, support effect, size effect, and structure effect. Finally, perspectives on the challenges and opportunities toward developing advanced Ru-based HOR electrocatalysts are also highlighted.