Engineering Interfacial Pt─O─Ti Site at Atomic Step Defect for Efficient Hydrogen Evolution Catalysis

The hydrogen evolution reaction (HER) activity of defect-stabilized low-Pt-loading catalysts is closely related with defect type in support materials, while the knowledge about the effect of higher-dimensional defects on the property and activity of trapped Pt atomic species is scarce. Herein, small size (5-10 nm) TiO₂ nanoparticles with abundant surface step defects (one kind of line defect) are used to direct the uniform anchoring of Pt atomic clusters (Pt-ACs) via Pt─O─Ti linkage. The as-made low-Pt catalysts (Pt-ACs/S-TiO₂-NP) exhibit exceptional HER intrinsic activity due to the unique step-site Pi-O-Ti species, in which the mass activity and turnover frequency are as high as 21.46 A mg _Pt ^-1 and 21.69 s^-1 at the overpotential of 50 mV, both far beyond those of benchmark Pt/C catalysts and other Pt-ACs/TiO₂ samples with less step sites. Spectroscopic measurements and theoretical calculations reveal that the step-defect-located Pt─O─Ti sites can simultaneously induce the charge transfer from TiO₂ substrate to the trapped Pt-ACs and the downshift of d-band center, which helps the proton reduction to H* intermediates and the following hydrogen desorption process, thus improving the HER. The work provides a deep insight on the interactions between high-dimensional defect and well-dispersed atomic metal motifs for superior HER catalysis.