Scientists have developed a scalable next-generation device that produces green hydrogen by splitting water molecules using only solar energy.

Green hydrogen is one of the cleanest fuels known, capable of decarbonizing industries, powering vehicles, and storing renewable energy. Yet, until now, scalable and affordable production methods remained elusive.

In a major leap in this direction, scientists from the Centre for Nano and Soft Matter Sciences (CeNS), Bengaluru, an autonomous institute of the Department of Science and Technology (DST), have developed a next-generation device that produces green hydrogen by splitting water molecules using only solar energy and earth-abundant materials, without relying on fossil fuels or expensive resources.

Led by Dr. Ashutosh K. Singh, the research team designed a state-of-the-art silicon-based photoanode using an innovative n-i-p heterojunction architecture, consisting of stacked n-type TiO₂, intrinsic (undoped) Si, and p-type NiO semiconductor layers, which work together to enhance charge separation and transport efficiency. The materials were deposited using magnetron sputtering, a scalable and industry-ready technique that ensures precision and efficiency. This thoughtful engineering approach allowed better light absorption, faster charge transport, and reduced recombination loss, key ingredients for efficient solar-to-hydrogen conversion.

This is more than just a lab success. The device achieved an excellent surface photovoltage of 600 mV and a low onset potential of around 0.11 V_RHE, making it highly effective at generating hydrogen under solar energy. Even more impressively, it showcased exceptional long-term stability, operating continuously for over 10 hours in alkaline conditions with only a 4% performance drop, a rare feat in Si-based photoelectrochemical systems.

This new device is attractive for several reasons, including high efficiency, low energy input, robust durability, and cost-effective materials, all in one package. It even demonstrated successful performance at a large scale, with a 25 cm² photoanode delivering excellent solar water-splitting results.

Fig: Schematic illustration of the n-i-p heterojunction photoanode showing charge transfer pathways for efficient solar water splitting. Inset images highlight the large-area photoanode (25 cm²) generating hydrogen under solar energy and its surface photovoltage response demonstrating strong photo-electrocatalytic activity and scalability.

“By selecting smart materials and combining them into a heterostructure, we have created a device that not only boosts performance but can also be produced on a large scale,” said Dr. Singh. “This brings us one step closer to affordable, large-scale solar-to-hydrogen energy systems.”

The work has been published in Journal of Materials Chemistry A, published by the Royal Society of Chemistry, and the researchers believe this is just the beginning. With further development, the technology could fuel hydrogen-based energy systems, from homes to factories, all powered by the sun.

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