doi:10.1038/nindia.2016.69 Published online 30 May 2016
By using three metal-based catalysts, researchers have developed a rapid technique that can simultaneously oxidize water and reduce carbon dioxide, generating formic acid that is potentially useful as a green fuel1. This technique could also help industries to cut their carbon dioxide emissions.
The researchers synthesized the three metal-based catalysts, using molybdenum, tungsten and reduced graphene oxide. The catalysts self-assembled in water to form vesicle-like superstructures known as soft oxometalates, which were used as active catalysts.
The catalysts accelerated the oxidation of water, producing oxygen, protons and electrons. These electrons then reduced carbon dioxide, forming formic acid and formaldehyde. The molybdenum- and graphene-conjugated catalysts finished oxidation and reduction in 40 minutes, whereas the tungsten-based catalyst completed the same reactions in 75 minutes under ultraviolet light.
Carbon dioxide reduction increased at lower pH levels, but water oxidation was disrupted at low pH. Since these reactions depend on the active surface area of the catalysts, their rate did not change with increasing catalyst load.
Exposure to ultraviolet light excited millions of photoactive clusters on the surfaces of the metal-based catalysts, contributing to their enhanced catalytic activity over conventional catalysts.
“In the future, these catalysts could potentially be used to make clean fuel for cars by reducing carbon dioxide and generating oxygen as a by-product,” says lead researcher Soumyajit Roy from the Indian Institute of Science Education and Research in Kolkata.
1. Das, S. et al. Photochemical reduction of carbon dioxide coupled with water oxidation using various soft-oxometalate (SOM) based catalytic systems. J. Mater. Chem. A (2016) DOI:10.1039/C6TA02825J