Graphene Oxide as an Ideal Substrate for Hydrogen Storage

Abstract

Organometallic nanomaterials hold the promise for molecular hydrogen (H(2)) storage by providing nearly ideal binding strength to H(2) for room-temperature applications. Synthesizing such materials, however, faces severe setbacks due to the problem of metal clustering. Inspired by a recent experimental breakthrough ( J. Am. Chem. Soc. 2008 , 130 , 6992 ), which demonstrates enhanced H(2) binding in Ti-grafted mesoporous silica, we propose combining the graphene oxide (GO) technique with Ti anchoring to overcome the current synthesis bottleneck for practical storage materials. Similar to silica, GO contains ample hydroxyl groups, which are the active sites for anchoring Ti atoms. GO can be routinely synthesized and is much lighter than silica. Hence, higher gravimetric storage capacity can be readily achieved. Our first-principles computations suggest that GO is primarily made of low-energy oxygen-containing structural motifs on the graphene sheet. The Ti atoms bind strongly to the oxygen sites with binding energies as high as 450 kJ/mol. This is comparable to that of silica and is indeed enough to prevent the Ti atoms from clustering. Each Ti can bind multiple H(2) with the desired binding energies (14-41 kJ/mol-H(2)). The estimated theoretical gravimetric and volumetric densities are 4.9 wt % and 64 g/L, respectively.