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 (BCx) 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 angstrom, large enough to allow the diffusion of hydrogen intercalated between BCx layers. Slower adsorption and desorption kinetics that depend sensitively on H-2 charging duration and temperature suggest the presence of hidden surface area of the turbostratic BCx and enhanced binding energy sites. Our study suggests that the increased c-plane spacing, together with a significant concentration of electron-deficient sp(2) boron sites, combine to create a stronger H-2 sorbent interaction than is typically achieved for undoped carbon sorbents.