Phase-dependent growth of Pt on MoS2 for highly efficient H2 evolution

13 Sep 2023

Published on nature (13 September 2023)

Author(s): Zhenyu Shi, Xiao Zhang, Xiaoqian Lin, Guigao Liu, Chongyi Ling, Shibo Xi, Bo Chen, Yiyao Ge, Chaoliang Tan, Zhuangchai Lai, Zhiqi Huang, Xinyang Ruan, Li Zhai, Lujiang Li, Zijian Li, Xixi Wang, Gwang-Hyeon Nam, Jiawei Liu, Qiyuan He, Zhiqiang Guan, Jinlan Wang, Chun-Sing Lee, Anthony R. J. Kucernak & Hua Zhang

Abstract

Crystal phase is a key factor determining the properties, and hence functions, of two-dimensional transition-metal dichalcogenides (TMDs). The TMD materials, explored for diverse applications, commonly serve as templates for constructing nanomaterials and supported metal catalysts. However, how the TMD crystal phase affects the growth of the secondary material is poorly understood, although relevant, particularly for catalyst development. In the case of Pt nanoparticles on two-dimensional MoS₂ nanosheets used as electrocatalysts for the hydrogen evolution reaction7, only about two thirds of Pt nanoparticles were epitaxially grown on the MoS₂ template composed of the metallic/semimetallic 1T/1T′ phase but with thermodynamically stable and poorly conducting 2H phase mixed in. Here we report the production of MoS₂ nanosheets with high phase purity and show that the 2H-phase templates facilitate the epitaxial growth of Pt nanoparticles, whereas the 1T′ phase supports single-atomically dispersed Pt (s-Pt) atoms with Pt loading up to 10 wt%. We find that the Pt atoms in this s-Pt/1T′-MoS₂ system occupy three distinct sites, with density functional theory calculations indicating for Pt atoms located atop of Mo atoms a hydrogen adsorption free energy of close to zero. This probably contributes to efficient electrocatalytic H2 evolution in acidic media, where we measure for s-Pt/1T′-MoS₂ a mass activity of 85 ± 23 A mg⁻¹_Pt at the overpotential of −50 mV and a mass-normalized exchange current density of 127 A mg⁻¹_Pt and we see stable performance in an H-type cell and prototype proton exchange membrane electrolyser operated at room temperature. Although phase stability limitations prevent operation at high temperatures, we anticipate that 1T′-TMDs will also be effective supports for other catalysts targeting other important reactions.

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a, Schematic illustration of preparing 1T′-MoS2 NSs from KxMoS2 crystals through the electrochemical intercalation (step 1) and subsequent exfoliation (step 2). b,c, TEM (b) and atomic force microscope (AFM) (c) images of the exfoliated 1T′-MoS2 NSs. c, The height profiles and measured thicknesses of 1T′-MoS2 NSs (insets). d, Thickness distribution histogram of 1T′-MoS2 NSs measured by AFM (1.4 nm is the mean thickness, and 0.4 nm is the s.d.). e, HAADF-STEM image of a typical 1T′-MoS2 NS. The corresponding fast Fourier transform pattern is shown in the inset. f, XPS spectra of exfoliated 1T′-MoS2 NSs and 2H-MoS2 NSs. The empty dots and the solid curves represent the experimental XPS data and the corresponding deconvoluted spectra, respectively. g, Raman spectra of exfoliated 1T′-MoS2 NSs and 2H-MoS2 NSs. a.u., arbitrary unit.