Spontaneous deposition of high-density Pt single atoms on oxides via charge polarization between oxides and carbon

Abstract

Although Pt exhibits high activity for the electrochemical hydrogen evolution reaction (HER), its high cost and scarcity limit its widespread application. Traditional Pt catalysts and Pt single-atom (Pt₁) catalysts (Pt₁-SACs) face challenges in maintaining kinetically favorable HER pathways (Volmer–Tafel) when using ultralow Pt amounts. Herein, a facile and scalable method for fabricating carbon-supported monodispersed Pt₁ on oxides (Pt₁/oxide/C) is proposed. Charge polarization between oxides and carbon facilitates the spontaneous formation of high-density Pt₁s (HD-Pt₁s) on oxide surfaces without requiring high-temperature calcination and reducing agents. The mean diameter and density of Pt₁ and the edge-to-edge distance between two adjacent Pt₁s were observed by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and measured by an electrochemical method. Pt₁/oxide/C exhibits 250-fold higher Pt mass activity (i_mPt)/turnover frequency (TOF) (485–580 A mg⁻¹/490–586 s⁻¹) than commercial Pt/C (1.9 A mg⁻¹/1.9 s⁻¹). At an ultralow Pt loading (∼0.19 μg cm⁻²), the HER rate-determining step remains Volmer–Tafel on Pt₁/oxide/C with HD-Pt₁s, with a 100% Pt utilization efficiency.