Scientists develop new hydrogen-generating photocatalyst model
A unique photocatalyst that can remove pollutants from water while simultaneously producing hydrogen using sunlight was developed by the scientists from the IIT Mandi, and researchers from Yogi Vemana University.
By combining mesocrystals of calcium titanate with edge sulfur atoms reduced graphene oxide and enriched molybdenum disulfide the scientists have developed a series of novel and multifunctional nanocomposite photocatalysts. The splitting of water into oxygen and hydrogen is a specific and beneficial example of a photocatalytic reaction. This reaction was already demonstrated by Fujishima and Honda as early as 1972, the inefficiency of the procedure has actually been a reason to halt in scaling up the technology. Additionally, these photocatalysts have been utilized in the degradation of organic pollutants present in water.
Dr. Venkata Krishnan, Associate Professor, School of Basic Sciences, IIT Mandi said, “The performance of a photocatalytic response depends upon the performance with which the photocatalyst transforms light energy into photogenerated charges that drives the required reaction”. Generating electron-hole pairs when subjected to the light of certain wavelengths, which generates the reaction they are meant to catalyze is how the photocatalysts function. Commonly studied photocatalyst are oxide products such as titania as
well as titanates, however, these materials are frequently inefficient on their own as the electrons and holes incorporate before the reaction can be propelled forward.Due to the free electrons that are generated flow between particles before they can recombine with the hole, “A new class of ‘superstructures’, made of highly ordered nanoparticles – Mesocrystals, could limit the recombination of electron-hole pairs”, said Dr. Krishnan.
He added, “A 33-fold enhanced photocatalytic hydrogen evolution over pure calcium titanate was showed by the mesocrystal-semiconductor-graphene combination. For the light of 3 different wavelengths, with apparent light-to-electron conversion efficiencies of 5.4%, 3%, and 17.7% – the highest efficiency was produced by orange light (600 nm)”. Making it promising for pollution control methods, our combination degrades many kinds of organic pollutants, when exposed to light.
3 key factors that attribute the enhancement in photocatalytic performance of their material combination as per Dr. Venkata Krishnan are: (1) The intimate contact between the 3 components, which leads to better electron transfer, (2) The high surface area provides more space for the reaction to take place, and (3) Certain sites on molybdenum disulfide (MoS2) that act as sticky sites for the positive hydrogen ions that are generated during the reaction, which, in turn, improves the production of hydrogen.
In the field of materials science, it may be known that graphene is the new “wonder material”, ever since its isolation earned the Nobel Prize. The scientists found that remarkable enhancement in photocatalytic activity could be achieved with their mesocrystal-semiconductor-graphene combination.
The research on the “hydrogen-generating photocatalyst model” is released in the journal ChemPhotoChem. The study was carried out by Dr. Venkata Krishnan, Associate Professor (Chemistry), School of Basic Sciences, Mr. Ashish Kumar and Mr. Ajay Kumar (his research scholars), IIT Mandi; and Dr. M. V. Shankar and Mr. Vempuluru Navakoteswara Rao (research scholar) from Yogi Vemana University.
