Direct synthesis of formic acid from carbon dioxide by hydrogenation in acidic media.

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.

Hydrogen storage: beyond conventional methods.

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.

Direct, in situ determination of pH and solute concentrations in formic acid dehydrogenation and CO(2) hydrogenation in pressurised aqueous solutions using (1)H and (13)C NMR spectroscopy.

In water, spin-lattice relaxation times (T(1)) and calibration curves for chemical shifts have been determined for the (13)C and the (1)H(C) atoms in HCOOH, HCOONa, CO(2), Na(2)CO(3) and NaHCO(3) by NMR spectroscopy. These data facilitate kinetic and mechanistic studies for H(2) storage/delivery in the carbon dioxide-formic acid systems under H(2) and CO(2) pressures.