AHMEDABAD: Researchers at the Indian Institute of Technology Gandhinagar (IITGN) have identified structural characteristics in monolayer amorphous carbon that could help in developing low-cost, metal-free catalysts for green hydrogen production, according to a computational study, The New Indian Express reported.
The research examines Monolayer Amorphous Carbon (MAC), a one-atom-thick carbon material that differs from graphene because its carbon atoms do not follow a long-range ordered arrangement. Researchers found that this structural disorder creates a broader range of local atomic environments, potentially increasing the number of sites where hydrogen-production reactions can occur.
The findings, published in npj 2D Materials and Applications, are significant in the context of efforts to reduce reliance on scarce and costly metals such as platinum and iridium, which are widely associated with water-splitting technologies.
In graphene, carbon atoms are arranged in a regular hexagonal pattern, resulting in a relatively limited range of active sites. MAC, by contrast, contains a combination of five-, six- and seven-membered carbon rings.
For the study, the researchers created a computational model of MAC using a melt-quench process. Carbon was first heated to disrupt its ordered structure and then rapidly cooled to retain the resulting disordered configuration.
The team subsequently used Density Functional Theory (DFT) calculations along with the machine-learning interatomic potential MACE to examine a much larger number of possible sites for hydrogen adsorption.
Approximately 1,183 sites across a larger MAC surface were analysed. The calculated hydrogen adsorption free-energy values ranged from −0.91 to +1.70 eV. Around 15% of the sites showed values below +0.25 eV, suggesting potentially favourable catalytic behaviour.
Sreehari M S, a third-year PhD scholar in IITGN’s Department of Materials Engineering and the study’s first author, said the effectiveness of a catalyst depends on maintaining an appropriate interaction between hydrogen and the catalytic surface.
“If hydrogen binds too strongly, its release becomes difficult; if the interaction is too weak, the reaction cannot proceed efficiently. A hydrogen adsorption free energy close to zero is therefore desirable,” he said.
The calculations showed that pristine graphene had a hydrogen adsorption free-energy value of about +1.73 eV. Among the crystalline carbon materials assessed, β-graphyne performed better, with a value of approximately +0.34 eV.
The researchers found that structural distortions played an important role in determining the adsorption behaviour. Bond distortions, irregular bond angles and greater surface rippling were linked to more favourable hydrogen adsorption. In contrast, areas that retained a structure more similar to graphene showed less favourable catalytic characteristics.
Dr Raghavan Ranganathan, Associate Professor in IITGN’s Department of Materials Engineering and Principal Investigator of the Computational Molecular Engineering Group, said the findings could provide a pathway for designing future catalysts.
The researchers cautioned that the findings are based on computational analysis and will require experimental validation to establish whether the material can deliver practical benefits for hydrogen production.
Ashutosh Krishna Amaram, who contributed to the research and is currently pursuing doctoral studies at the University of Illinois Chicago and Argonne National Laboratory, said machine learning allowed the team to assess a large number of potential catalytic sites that would have been difficult to study using DFT calculations alone.
The simulations were conducted using IITGN’s Param Ananta supercomputing facility. The researchers said the work could contribute to future screening of carbon-based materials before they are synthesised and subjected to experimental testing.
The study also supports the broader objectives of India’s National Green Hydrogen Mission, which aims to expand domestic green hydrogen production and use while improving the cost and efficiency of technologies associated with its production.
