高导电性和催化活性的Janus-TiNbCO_(2)析氢反应催化材料

Janus-TiNbCO_(2) for Hydrogen Evolution Reaction with High Conductivity and Catalytic Activity

探寻具有高导电性和高催化活性的析氢反应(HER)催化材料一直是可持续能源发展研究中的热点。Ti_(2)C具有表面活性位点多和优良的力学稳定性、导电性等,已成为潜在的制氢催化剂。然而,终端O修饰Ti_(2)C表面,会降低该材料的导电性,进而限制了电子在价带与导带间的输运。本研究通过Nb掺杂,构建双电层Janus-TiNbCO_(2),并借助VASP软件研究了Janus-TiNbCO_(2)的能带结构、HER性能和HER反应路径过渡态。结果表明,Janus-TiNb-CO_(2)为导体材料,其在应力、氧空位缺陷和H^(*)覆盖度的影响下,均表现出极优异的催化活性,计算获得的最优△G_(H^(*))值为0.02 eV。H^(*)在Janus-TiNbCO_(2)上可能以Heyrovsky路径进行反应,该路径的迁移能势垒为0.23 eV。Janus-TiNbCO_(2)是一种具有HER应用前景的催化材料。

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.Ti_(2)C,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 Ti_(2)C 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-TiNbCO_(2)was constructed by Nb doping.The band property,HER activity and HER reaction path of Janus-TiNbCO_(2)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-TiNbCO_(2)comparing with that of Ti_(2)CO_(2)structure.The Janus-TiNbCO_(2)structure is stable by calculating the thermodynamic stability at 500 K using AIMD method.The band gap of Ti_(2)CO_(2)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-TiNbCO_(2)has the metal band structure.In Janus-TiNbCO_(2),both Ti and Nb surfaces adsorb H^(*)by O site,where the△G_(H^(*))(@Ti)=-0.55 eV,△G_(H^(*))(@Nb)=0.02 eV,showing Ti and Nb surfaces have different catalytic activities.Comparing with graphenes,e.g.,h-B_(2)O,Pt,and g-C_(3)N_(4),Janus-TiNbCO_(2)has better catalytic activity.The charge distribution of Janus-TiNbCO_(2)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-TiNbCO_(2)are studied.When the H^(*)coverage is low,the optimal△G_(H^(*))of Nb surface is approximate 0.02 eV,while Ti surface has an excellent catalytic activity at high H^(*)coverages(θ=7/9,△G_(H^(*))=-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-TiNbCO_(2).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-TiNbCO_(2)can be used as a potential HER catalyst.