Manipulation in local coordination of platinum single atom enables ultrahigh mass activity toward hydrogen evolution reaction

Atomic-engineering of noble metal into single-atom electrocatalysts with well-defined active sites has been considered as an effective approach to enhance the mass-activity towards hydrogen evolution reaction (HER), crucial for the practical implementation of this sustainable technology. Herein, we devise a metallic-coordination strategy via a facile one-step pyrolysis method, for the atomic isolation of a small amount of platinum (Pt, 0.45 wt%) atoms in the surface of nickel (Ni) nanoparticles (Pt₁@Ni) encapsulated into nitrogen-doped carbon nanotubes (Pt₁@Ni/NCNT). Such a Pt₁@Ni/NCNT single-atom alloy catalyst exhibits a record-high and all-round superior HER performance including mass-activity (up to 350.7 A mg_Pt⁻¹@η₁₅₀), stability (>50 h at 100 mA cm⁻²), pH-tolerance by comparison with Pt₁@NC. Our density functional theory calculations combined with in situ Raman spectroscopic studies reveal a synergistic dual-active-site catalytic mechanism, involving the fast hydrogen spillover effect on coordinated Ni supports and accelerated water dissociation in acidic and alkaline medium, respectively. A strong electronic hybridization of 5d orbital of alloyed Pt and 3d orbital of Ni atoms modulates the d band center of Pt, which not only boosts HER activity but also stabilizes Pt single atoms. Due to the double protecting strategy from strong anchoring effect in Ni support and chemically stable NCNT shell, a robust stability is achieved for Pt₁@Ni/NCNT hierarchal catalyst. Our findings open up a new avenue to substantially tailor the activity of surface Pt atoms for the design of highly efficient and durable noble metal-based catalysts.