Scientists at the Centre for Nano and Soft Matter Sciences (CeNS), Bengaluru, have developed a metal-free organic material that could support solar-driven green hydrogen production by using naturally occurring molecules to improve photocatalytic water splitting.
The material combines the amino acid aspartic acid with the light-absorbing organic molecule perylene diimide (PDI). When integrated in water, the molecules spontaneously form highly ordered two-dimensional nanosheets, with the resulting material generating nearly 18% higher photocurrent than its bulk counterpart during solar-driven water splitting.
Self-assembly improves photocatalytic performance
The research addresses a key challenge in solar hydrogen production: developing efficient photocatalysts without relying on costly or scarce metals.
Many existing photocatalytic systems use inorganic semiconductors or precious metals. The CeNS approach instead uses organic molecules and exploits their ability to organise themselves at the molecular level.
The researchers synthesised an aspartic acid-functionalised PDI molecule that undergoes supramolecular self-assembly in water. This process produces an ordered nanosheet structure that changes how the material absorbs light and transports electrical charges.
Aspartic acid and PDI perform complementary roles
The researchers attribute the material’s enhanced performance to the interaction between its two molecular components.
Aspartic acid promotes strong and extended hydrogen bonding, helping determine the organisation of the molecular structure. PDI, meanwhile, contributes π–π stacking and efficient light absorption.
The resulting molecular arrangement affects the material’s photocatalytic behaviour, including the movement and separation of charges generated when the material absorbs sunlight.
Material delivers higher photocurrent
The molecular reorganisation broadened the material’s light absorption and improved charge separation while reducing energy losses, according to the researchers.
It also increased the surface area available for catalytic reactions. During solar-driven water splitting, the self-assembled material generated nearly 18% higher photocurrent than the corresponding bulk material.
Photocurrent is the electrical current generated when light produces charge carriers in a material. Higher photocurrent can indicate more effective conversion of absorbed light into usable electrical charge, although it does not by itself establish a corresponding percentage increase in hydrogen production.
Advanced analysis reveals charge-transport mechanism
The CeNS team used advanced electrochemical measurements and density functional theory (DFT) calculations to investigate how self-assembly affects the material’s properties.
The analysis indicated that molecular organisation enables more efficient charge transport.
The researchers also found that the amino acid component increases the material’s molecular dipole moment, which can help separate photo-generated charges and support hydrogen evolution.
This relationship between molecular structure and photocatalytic behaviour is central to the study. Rather than treating the organic molecules simply as chemical ingredients, the research uses molecular organisation itself as a design tool.
Organic molecules could reduce dependence on metals
The study demonstrates that naturally occurring amino acids can serve two functions in photocatalytic materials: they can act as molecular building blocks while also regulating the supramolecular structure responsible for performance.
This could provide another route towards designing photocatalysts that avoid precious or scarce metals.
The researchers said the approach could support the development of more sustainable and environmentally friendly metal-free materials for solar energy conversion.
Potential applications extend beyond hydrogen
The research team said materials based on the molecular design approach could have potential applications in green hydrogen production, artificial photosynthesis, solar fuel generation and next-generation renewable energy devices.
The study was led by Dr Goutam Ghosh and Dr Ashutosh K. Singh of CeNS, Bengaluru, together with Sourav Moyra, Kumar Shubham and Athira Chandran M.
The findings have been published in the Journal of Materials Chemistry A, a journal of the Royal Society of Chemistry.
The work remains a materials-research development rather than a commercial hydrogen-production technology. Its significance lies in demonstrating how self-assembling organic molecules can be engineered to improve the properties of metal-free photocatalysts for solar energy conversion.
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The CeNS research highlights a different pathway to green hydrogen production that focuses on molecular engineering rather than conventional metal-containing photocatalysts. The nearly 18% increase in photocurrent is a measurable improvement in the material’s solar-driven electrochemical performance, but further development would be needed to establish its practical hydrogen-production efficiency, durability and scalability.
For the wider hydrogen sector, the research is relevant because reducing dependence on costly or scarce materials could eventually address part of the materials challenge associated with solar fuel technologies. The immediate significance is therefore at the photocatalyst-development stage, with commercial relevance depending on whether the molecular system can maintain its performance under longer-term and larger-scale operating conditions.
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