Formic Acid

There are several ways of making formates from hydrogen and sodium bicarbonate, potassium bicarbonate or ammonium bicarbonate, in the presence of various different catalysts.

Noting that one of the proposed methods of  Direct CO₂ capture from the Atmosphere (DACC) was to run air through sodium or ammonium hydroxide, which could produce sodium or ammonium bicarbonate, it might be a useful addition to that process.

It is also possible to make Formic acid from syngas. Methanol and methyl formate HCO₂CH₃ (also called methyl methanoate) are usually produced as well. Methyl methanoate is liquid at STP, so might be a reasonable chemical to start with when trying to create something more dense for basic carbon storage, if it could be made directly from atmospheric CO₂.

There are also some methods from mixing H₂ and CO₂ at reasonably high pressures, about 20 atmospheres in the presence of a different metal  catalysts which will produce formic acid directly. Some of these happen faster if the metal is spread out across a specific structure of surface.

Other catalysts used have a particular molecular shape that seems to make the hydrogenation reaction happen faster. There is a lot of active research into these methods, but it is not clear if any of the processes are yet actually being used commercially or industrially.

The most promising option is described in a paper published in Nature in 2012, which uses an iridium catalyst distributed within an organic chemical with a particularly useful molecular structure and close to ambient conditions.

A general problem with formic acid is that it tends to eat its way through metals, and indeed a problem with many of the metallic catalysts used in the process is that the metal leaches away over a relatively short time.