Potassium-doped PC 71 BM for hydrogen storage: Photoelectron spectroscopy and first-principles studies

We consider the fullerene C 70 derivative PC 71 BM as a potential onboard hydrogen storage material. As the cases of many sorbents, metal-decoration is needed to increase the adsorption energy of H 2. We study the metal-decoration by intercalating K atoms into a PC 71 BM film and performing photoelectron spectroscopy measurements. The results reveal that the maximum stoichiometry is K 9 – 10 PC 71 BM. Then we study the hydrogen storage property of an isolated K 9 PC 71 BM molecule with density functional theory calculations. A K 9 PC 71 BM molecule can compactly adsorb 45H 2 (6.22 wt%); the compact adsorption structure does not require large interstitial space in solid phase and thus should be able to be realized in experiments. Considering the poor crystallinity of solid PC 71 BM (with many large interstitial spaces), a gravimetric capacity >7 wt% can be anticipated. The adsorption energy meets the DOE target of onboard operating temperatures, and van der Waals interaction contributes more than 40% of the adsorption energy.