Manipulation of Hydrogen Binding Energy and Desorption Kinetics by Boron Doping of High Surface Area Carbon

Boron-doped high surface area carbon is shown to have unique chemical and structural properties that are advantageous for hydrogen storage. High surface area boron-doped carbon sorbents were produced by chemical vapor deposition of a boron-doped carbon (BC_X) layer onto CM-Tec activated carbon. Photoelectron spectroscopy indicates the incorporation of boron at levels up to 14.3 at. % into sites with varying bonding environments. High-resolution microscopy characterization demonstrates that the turbostratic boron-carbon layer has a c-plane spacing of 4.02 ± 0.24 Å, large enough to allow the diffusion of hydrogen intercalated between BC_X layers. Slower adsorption and desorption kinetics that depend sensitively on H₂ charging duration and temperature suggest the presence of hidden surface area of the turbostratic BC_X and enhanced binding energy sites. Our study suggests that the increased c-plane spacing, together with a significant concentration of electron-deficient sp² boron sites, combine to create a stronger H₂-sorbent interaction than is typically achieved for undoped carbon sorbents.