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While efficient for electrochemical hydrogen evolution reaction (HER), Pt is limited by its cost and rarity. Traditional Pt catalysts and Pt single-atom (aPt) catalysts (Pt-SACs) face challenges in maintaining kinetically favorable HER pathways (Volmer–Tafel) at ultralow Pt loadings. Herein, carbon-promoted aPts were deposited on RuO2 without the addition of reductants. aPts confined on carbon-supported RuO2 nanorods (aPt/RuO2NR/Carbon) promoted "inter-aPts" Tafel. aPt/RuO2NR/Carbon is the Pt-SAC that retained underpotentially deposited H; additionally, its HER onset overpotential was "negative". The aPt/RuO2NR/Carbon exhibited 260-fold higher Pt mass activity (imPt)/turnover frequency (TOF) (522.7 A mg–1/528.4 s–1) than that of commercial Pt/C (1.9 A mg–1/1.9 s–1). In an ultralow Pt loading (0.19 μg cm–2), the HER rate-determining step maintained Volmer–Tafel and the Pt utilization efficiency was 100.3%.
Huang et al. (Fri,) studied this question.