An Electrocatalyst with Dense Single-Atom Platinum Sites for Hydrogen Evolution Reaction

Abstract Platinum (Pt) is widely used in proton exchange membrane water electrolyzers (PEMWEs) for hydrogen (H2) production due to its intrinsically high activity for the cathodic hydrogen evolution reaction (HER). However, its usage is expected to be further reduced to improve the H2 cost-competitiveness. Herein, enabled by ultrafast Joule heating in a reductive gas environment, we successfully transform carbon black substrates loaded with a Pt-containing heteropolyoxotungstate (Pt-POM) into a catalyst (Pt1W6Ox/C) with up to 7.85 wt % of single Pt atom sites. The Pt atoms are anchored on defective tungsten oxide nanoislands, which play critical roles in stabilizing the low-valence Pt single atom with near-optimal H* adsorption strength, enabling efficient electron transfer from the carbon substrate via strong W–C bonds, and increasing local proton concentration with their fast and reversible proton insertion/extraction kinetics, as identified by operando measurement and theoretical calculations. Consequently, this catalyst exhibits good HER performance, affording a Pt mass-specific activity of 2.71 A mgPt−1 at an overpotential of 10 mV, nearly 26 times greater than the commercial 20 wt % Pt/C catalyst. Moreover, benefiting from the dense active sites, this catalyst can deliver a current density of 3 A cm−2 at 1.804 V in a PEMWE prototype, showing great potential for practical applications.