Researchers at the Indian Institute of Technology (IIT), Mandi, have developed a novel carbon-based catalyst to make water electrolysis more efficient, as well as being more stable and affordable than other catalysts that perform the same function.
The findings were published in the journal Carbon Trends in October 2022.
The electrolysis of water — to split it into its constituent atoms using electricity — consumes a lot of energy. The traditional solution is to use a catalyst to induce the water molecules to split at a lower energy. Common catalysts are based on iridium and ruthenium, which are expensive and in great demand in other sectors.
In the new study, research groups of Assistant Professor Swati Sharma and Associate Professor Aditi Halder reported a porous carbon material containing nitrogen that functions both as a catalyst and as the anode in electrolysers, and could substitute the metal-based catalysts.
The researchers produced this material, called ‘laser carbon’, by exposing a sheet of a polyimide polymer to a laser beam, carbonising the exposed bits and leaving the remainder rich in nitrogen.
In an electrolyser, the nitrogen atoms drew electron clouds towards themselves, encouraging nearby carbon atoms to bond with atoms or molecules containing electron pairs. So, the location of these atoms became active sites for the oxygen evolution reaction (OER).
The OER is a stumbling block in electrolysis because it has many intermediate steps and proceeds slower than the rest of the reaction cycle, thus reducing the energy efficiency.
Laser carbon intervenes by reducing the OER overpotential: the difference between the voltage at which the OER takes place in reality and the minimum voltage at which it can take place. Lowering the overpotential allows OER to proceed vigorously.
According to Dr. Sharma, laser carbon is simpler to synthesise, and “can be batch-manufactured with a laser” in an environmentally friendly process, unlike other carbon-based catalysts.
Dr. Halder also said the production process increases the surface area laser carbon present to catalyse the reaction.
While the researchers also said that the material’s catalytic activity is inferior to that of metal-based catalysts, it can be improved “in the fabrication process and use of other polymers”.
(Sunderarajan Padmanabhan is a Delhi-based freelance science correspondent)
