Importance of hydrogen bond configuration on lattice thermal conductivity of hydrogenated borophene

Due to the electron deficiency of boron, two-dimensional boron systems and its derivatives have a great diversity of configurations, such as the hydrogenated borophene, providing a promising platform to realize different electronic and thermal functions. In this work, using first-principles calculations combined with phonon Boltzmann transport equation, we study the lattice thermal conductivity (κL) of two hydrogenated borophene structures with different B–H bond configurations. We find that the κL of hydrogenated borophene can be doubled, when the B–H bond is replaced by the bridged B–H–B bond. Benefit from the electron deficiency of boron, the bridged B–H–B bond can provide electrons to the borophene layer, generating stronger B–B covalent bonds. This configuration further results in the blue-shift of phonon modes as well as the bunching effect for acoustic branches, which simultaneously increase the phonon group velocity and suppress the phonon–phonon scatterings, consequently enhancing the thermal conductivity. Our work offers an effective approach to optimize lattice thermal conductivity of two-dimensional materials via structure engineering, without varying the material content.