Hancheng Ma,Xiang Huang,Luyu Li,Wei Peng,Sheng Lin,Yao Ding,Liqiang Mai
PtTe 2 , a member of the noble metal dichalcogenides (NMDs), has aroused great interest in exploring its behavior in the hydrogen evolution reaction (HER) due to the unique type-II topological semimetallic nature. In this work, a simple template-free hydrothermal method to obtain the phosphorus-doped (P-doped) PtTe 2 nanocages with abundant amorphous and crystalline interface (A/C-P-PtTe 2 ) is developed. Revealed by density functional theory calculations, the atomic Te vacancies can spontaneously form on the basal planes of PtTe 2 by the P doping, which results in the unsaturated Pt atoms exposed as the active sites in the amorphous layer for HER. Owing to the defective structure, the A/C-P-PtTe 2 catalysts have the fast Tafel step determined kinetics in HER, which contributes to an ultralow overpotential ( η = 28 mV at 10 mA cm −2 ) and a small Tafel slope of 37 mV dec −1 . More importantly, benefiting from the inner stable crystalline P-PtTe 2 nanosheets, limited decay of the performance is observed after chronopotentiometry test. This work reveals the important role of the inherent relationship between structure and activity in PtTe 2 for HER, which may bring another enlightenment for the design of efficient catalysts based on NMDs in the near future.
The recent discovery of topological semimetals has stimulated extensive research interest due to their unique electronic properties and novel transport properties related to a chiral anomaly. However, the studies to date are largely limited to bulk crystals and exfoliated flakes. Here, we report the controllable synthesis of ultrathin two-dimensional (2D) platinum telluride (PtTe2) nanosheets with tunable thickness and investigate the thickness-dependent electronic properties. We show that PtTe2 nanosheets can be readily grown, using a chemical vapor deposition approach, with a hexagonal or triangular geometry and a lateral dimension of up to 80 μm, and the thickness of the nanosheets can be systematically tailored from over 20 to 1.8 nm by reducing the growth temperature or increasing the flow rate of the carrier gas. X-ray-diffraction, transmission-electron microscopy, and electron-diffraction studies confirm that the resulting 2D nanosheets are high-quality single crystals. Raman spectroscopic studies show characteristics Eg and A1g vibration modes at ∼109 and ∼155 cm–1, with a systematic red shift with increasing nanosheet thickness. Electrical transport studies show the 2D PtTe2 nanosheets display an excellent conductivity up to 2.5 × 106 S m–1 and show strong thickness-tunable electrical properties, with both the conductivity and its temperature dependence varying considerably with the thickness. Moreover, 2D PtTe2 nanosheets show an extraordinary breakdown current density up to 5.7 × 107 A/cm2, the highest breakdown current density achieved in 2D metallic transition-metal dichalcogenides to date.
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