Ultrahigh Electron Thermal Conductivity in T-Graphene, Biphenylene, and Net-Graphene

Although isolated nonhexagonal carbon rings in graphene are associated with strain relaxation and curvature, dense and ordered arrangements of four-, five-, and eight-membered rings with strained carbon–carbon bonds can tile 2D planar layers. Using the Boltzmann transport equation formalism in combination with density functional theory calculations, how the presence of nonhexagonal rings impacts the thermal conductivity of three 2D carbon allotropes: T-graphene (four and eight rings), biphenylene (four, six, and eight rings), and net-graphene (four, six, and eight rings), is investigated. The phonon thermal conductivity (κph), which captures three-phonon, four-phonon, and phonon–electron interactions, is significantly lowered with respect to pristine graphene. In compensation, the electron thermal conductivity (κe), which captures electron–phonon interactions, is enhanced to record high values, such that the room-temperature total thermal conductivity κtotal = κph + κe approaches the values of pristine graphene. 2D carbon allotropes could be of interest for applications requiring thermal energy transfer by a combination of diffusion of electrons and phonon vibrations.