Formic acid has recently been suggested as a promising hydrogen storage material. The basic concept is briefly discussed and the recent advances in the development of formic acid dehydrogenation catalysts are shown. Both the state of research for heterogeneous and for homogeneous catalyst systems are reviewed in detail and an outlook on necessary development steps is presented. Formic acid is considered as one of the most promising materials for hydrogen storage today. There are a number of highly active and robust homogeneous catalysts that selectively decompose formic acid to H₂ and CO₂ near to room temperature. Although the activity and selectivity of heterogeneous catalysts have not yet reached the level of homogeneous systems, this gap is closing.

Hydrogen is one of the essential reactants in the chemical industry, though its generation from renewable sources and storage in a safe and reversible manner remain challenging. Formic acid (HCO₂H or FA) is a promising source and storage material in this respect. Here, we present a highly active iron catalyst system for the liberation of H₂ from FA. Applying 0.005 mole percent of Fe(BF₄)₂·6H₂O and tris[(2-diphenylphosphino)ethyl]phosphine [P(CH₂CH₂PPh₂)₃, PP₃] to a solution of FA in environmentally benign propylene carbonate, with no further additives or base, affords turnover frequencies up to 9425 per hour and a turnover number of more than 92,000 at 80°C. We used in situ nuclear magnetic resonance spectroscopy, kinetic studies, and density functional theory calculations to explain possible reaction mechanisms.

The chemical transformation of carbon dioxide into useful products becomes increasingly important as CO2 levels in the atmosphere continue to rise as a consequence of human activities. In this article we describe the direct hydrogenation of CO2 into formic acid using a homogeneous ruthenium catalyst, in aqueous solution and in dimethyl sulphoxide (DMSO), without any additives. In water, at 40 °C, 0.2 M formic acid can be obtained under 200 bar, however, in DMSO the same catalyst affords 1.9 M formic acid. In both solvents the catalysts can be reused multiple times without a decrease in activity. Worldwide demand for formic acid continues to grow, especially in the context of a renewable energy hydrogen carrier, and its production from CO2 without base, via the direct catalytic carbon dioxide hydrogenation, is considerably more sustainable than the existing routes.

The efficient storage of hydrogen is one of three major hurdles towards a potential hydrogen economy. This report begins with conventional storage methods for hydrogen and broadly covers new technology, ranging from physical media involving solid adsorbents, to chemical materials including metal hydrides, ammonia borane and liquid precursors such as alcohols and formic acid.