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Journal of Electrochemistry ›› 2021, Vol. 27 ›› Issue (5): 570-578.  doi: 10.13208/j.electrochem.201109

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Janus-TiNbCO2 for Hydrogen Evolution Reaction with High Conductivity and Catalytic Activity

Li-Li Xu1,*(), Dong-Yan Ren1, Xiao-Feng Zhao2,3,*(), Yong Yi2   

  1. 1. Mianyang Vocational and Technical College, Department of Materials Enginerring, Mianyang 621000, Sichuan, China
    2. School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang 621010, Sichuan, China
    3. Department of Physics and Astronomy, Uppsala University, 75120 Uppsala, Sweden
  • Received:2020-11-09 Revised:2020-12-22 Online:2021-10-28 Published:2021-02-09
  • Contact: Li-Li Xu,Xiao-Feng Zhao E-mail:ll-xu2008@163.com;xfz_33@126.com


Exploring the potential hydrogen evolution reaction (HER) catalysts with the high activity and high conductivity has always been a hot spot in the research of renewable energy development. Ti2C, as one of the 2D-MXene, has excellent properties relating to many active sites, mechanical stability, conductivity, etc., and has become a potential HER catalyst. However, the modification of the surface of Ti2C by terminal O will reduce the conductivity, thereby limiting the transport of electrons between the valence band and the conduction band. In this study, an electric double layer Janus-TiNbCO2 was constructed by Nb doping. The band property, HER activity and HER reaction path of Janus-TiNbCO2 are studied by the first-principles calculations. The results show that Nb doping increases the distance between Ti and O atoms, which increases the lattice parameters of Janus-TiNbCO2 comparing with that of Ti2CO2 structure. The Janus-TiNbCO2 structure is stable by calculating the thermodynamic stability at 500 K using AIMD method. The band gap of Ti2CO2 is approximate 0.9 eV. After Nb doping, the orbital hybridization between Nd-3d and O-2p affects the electronic rearrangement of Ti-3d, leading that Janus-TiNbCO2 has the metal band structure. In Janus-TiNbCO2, both Ti and Nb surfaces adsorb H* by O site, where the ΔGH*(@Ti) = -0.55 eV,ΔGH*(@Nb) = 0.02 eV, showing Ti and Nb surfaces have different catalytic activities. Comparing with graphenes, e.g., h-B2O, Pt, and g-C3N4, Janus-TiNbCO2 has better catalytic activity. The charge distribution of Janus-TiNbCO2 near the Fermi level was analyzed by HSE-06 function. The result reveals that O atoms on the Ti surface exhibit charge unsaturation at the Fermi level, while those on Nb surface strong saturation. Moreover, the effects of H* coverage and strains(+2% ~ +4%) on the catalyst activity of Janus-TiNbCO2 are studied. When the H* coverage is low, the optimal ΔGH* of Nb surface is approximate 0.02 eV, while Ti surface has an excellent catalytic activity at high H* coverages (θ = 7/9, ΔGH* = -0.06 eV). Under the strain action, the H* coverage on surface is not affected. However, strains will reduce the HER activity of Nb surface, and increase the HER activity of Ti surface. Furthermore, oxygen defect is a stable point defect in Janus-TiNbCO2 . Oxygen defect will increase the HER activity of Ti surface and decrease the HER activity of Nb surface. Comparing to the Tafel pathway, the Heyrovsky is a more suitable pathway for the HER, in which the migration barrier of Heyrovsky is 0.23 eV for H* on Nb surface. Janus-TiNbCO2 can be used as a potential HER catalyst.

Key words: MXene, Janus-TiNbCO2, band, hydrogen evolution reaction