In Situ Preparation of Pt Nanoparticles Supported on N‑Doped Carbon as Highly Efficient Electrocatalysts for Hydrogen Production

We describe here that the electrode materials toward the hydrogen evolution reaction (HER) can be cathodically activated by anodic dissolution of Pt counter electrode, dependent on the nature of substrate materials and solution pH. It leads to a direct approach for in situ fabrication of a highly dispersed and active HER electrocatalyst with minimal Pt loading that requires only a piece of Pt (instead of Pt salt, such as K2PtCl6) as Pt source combined with judicious choices of substrate materials and electrolyte solution. For a typical sample obtained by pyrolyzing poly­(2,6-diaminopyridine) (PDAP) under ammonia atmosphere followed by successive cyclic voltammetry scans in 0.5 M H2SO4, a current density of 60 mA cm–2 was obtained at an overpotential of only 50 mV. Although the Pt loading is only 1.5 wt % in the sample, this performance is even better than that of the commercial 20 wt % Pt/C. The experimental results indicate that the deposited Pt nanoparticles are highly dispersed on the electrode substrate with a size of 2–4 nm. Further experimental results suggest that the combination of three factors, including the slow release of Pt into solution, high specific surface area of the substrate materials, and homogeneously doped N atoms acting as Pt anchor sites, is the key for formation of the highly active Pt nanoparticles. This study thus also raises an alarm regarding the use of Pt counter electrode in HER catalysis, especially by N-doped carbon in an acidic solution.