Hierarchical assembly of Pt single atoms and WC nanocrystals on porous carbon Boosting hydrogen evolution reactions

Optimizing the accessibility and chemical microenvironment of Pt single atoms (SAs) is essential for enhancing the efficiency of hydrogen evolution reaction (HER). Herein, we present a hierarchical catalyst (Pt 3 /WC/HS) featuring highly accessible Pt SAs moderately coordinated with WC nanoparticles and uniformly anchored on monodisperse porous carbon nanospheres. With a Pt content of 2.8 wt%, Pt 3 /WC/HS achieves an ultralow overpotential of 8 mV at 10 mA cm −2 , outperforming commercial 20 wt% Pt/C. Additionally, the catalyst exhibits outstanding HER activity in proton exchange membrane water electrolyzers (PEMWE), simulated seawater, and neutral media. Notably, in a coal-assisted hydrogen production system that decouples oxygen evolution reaction (OER) from HER, Pt 3 /WC/HS achieves 400 mA cm −2 at an applied potential of just 0.5 V. Spectroscopic characterizations and density functional theory (DFT) reveal that WC stabilizes the Pt SAs while retaining an active electronic configuration in the Pt 5 d z 2 orbital, shifting *H adsorption from thermodynamically unfavorable to spontaneous. Moreover, the interconnected porous framework of Pt 3 /WC/HS ensures high Pt site accessibility at the three-phase interface. This work demonstrates a versatile and high-performance HER catalyst suitable for diverse hydrogen evolution systems and offers a rational design strategy for single-atom catalysts.