A process that allows hydrogen to be efficiently sourced from liquid formic acid could represent a step forward in making hydrogen-powered cars an economic reality.
Using formic acid to produce hydrogen traditionally has not been considered viable because it requires high temperatures to decompose and produces waste by-products. But an international team led by Richard O’Hair, professor at the University of Melbourne School of Chemistry, has designed a molecular catalyst that forces formic acid to produce only hydrogen and carbon dioxide—and at a temperature of only 70 degrees Celsius.
“One of the grand challenges for chemists today is to develop perfect chemical reactions that proceed with 100% yield and 100% selectivity without forming any waste products,” O’Hair notes. “With formic acid, the aim was to transform it into hydrogen and carbon dioxide, which could really lend itself to the important practical applications of hydrogen energy in the transport sector.”
Using a suite of powerful gas-phase techniques, the research team designed a series of silver complexes and examined their reactions with formic acid. The team was able to identify and orchestrate the exact catalyst that would effectively manipulate a strict hydrogen/carbon dioxide-only production.
“I prepared solutions containing well-defined amounts of the same silver, salt and ligand combination, and these were studied [using nuclear magnetic resonance spectroscopy], which allowed us to incrementally increase the temperature from 25 degrees Celsius and track the formation of products," O’Hair explains. “There was no reaction for a while, but we persevered and at 70 degrees Celsius, we unequivocally identified the production of hydrogen gas and carbon dioxide."
One of the major challenges as the world moves toward hydrogen power is the lack of refueling infrastructure. But the researchers say that that could easily be overcome if the industry moves to using liquid formic acid.
And while the new catalyst design is an important step forward in addressing hydrogen energy production, O'Hair cautions that there are still barriers to overcome, such as the production of carbon dioxide and how it could potentially be recycled to regenerate formic acid.