This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Finding alternatives to precious metals in chemical manufacturing may be less like sourcing a substitute and more like tuning an instrument already in hand. Yokohama National University scientists have found that an earth-abundant cobalt catalyst can selectively hydrogenate nitrogen-containing compounds when the balance between metallic cobalt and cobalt oxide is carefully tuned.
Their findings could allow for more sustainable approaches to chemical manufacturing that do not depend on precious metals. The study is published in the Journal of the American Chemical Society. From medicines to plastics, many products we rely on every day begin with chemical transformations that require carefully designed catalysts.
One important example is hydrogenation, which adds hydrogen to molecules to produce useful chemical compounds. Conventional hydrogenation commonly relies on hydrogen gas, but electrocatalytic hydrogenation can generate hydrogen equivalents from water using electricity. This offers a potentially more sustainable approach to reductive chemical transformations, particularly when powered by renewable electricity.
This technology, however, has its own shortcomings. "A major challenge in electrocatalytic hydrogenation is replacing scarce platinum-group metals with earth-abundant catalysts without sacrificing activity or selectivity," said Mahito Atobe, a professor at Yokohama National University's Faculty of Engineering and a corresponding author of the study. In a quest for alternatives, the team turned to cobalt, an abundant and economical metal.
"We wanted to understand how the oxidation state of cobalt changes under operating conditions and whether controlling the balance between metallic cobalt and cobalt oxide could provide an effective catalyst," said Naoki Shida, an associate professor in the same faculty and a co-corresponding author. The researchers prepared their catalyst from cobalt sulfate and calcined it at 750 °C (1,382°F). They then tested it in an anion-exchange membrane electrolyzer, in which electricity drives hydrogenation reactions.
The optimized catalyst converted pyridine to piperidine with a yield of more than 99% under ambient electrolysis conditions. In other words, almost all of the pyridine that reacted was converted into the desired product rather than unwanted byproducts. Piperidine is an important building block in synthetic and medicinal chemistry, making this reaction a useful test of the catalyst's ability to carry out selective hydrogenation.
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