Hydrogen Storage in Formic Acid – Amine Adducts

Abstract

Formic acid, containing 4.4 wt% of hydrogen, is a non-toxic liquid at ambient temperature and therefore an ideal candidate as potential hydrogen storage material. Formic acid can be generated via catalytic hydrogenation of CO₂ or bicarbonate in the presence of an amine with suitable ruthenium catalysts. In addition selective dehydrogenation of formic acid amine adducts can be carried out at ambient temperatures with either ruthenium phosphine catalyst systems as well as iron-based catalysts. In detail we obtained with the [RuCl²(benzene)]₂/ dppe catalyst system a remarkable TON of 260,000 at room temperature. Moreover applying Fe₃(CO)₁₂ together with tribenzylphosphine and 2,2’:6’,2’’-terpyridine under visible light irradiation a TON of 1266 was obtained, which is the highest activity known to date for selective dehydrogenation of formic acid applying non-precious metal catalysts.