A team of researchers from Imperial College London and Queen Mary University of London have unveiled a major breakthrough in clean hydrogen production, revealing a new method of harnessing sunlight to produce hydrogen sustainably and at low cost.
The research, which was published in Nature Energy, highlights how organic photoactive materials can be adapted to deliver high efficiency and long-term stability in solar water splitting – a key process in generating hydrogen from water.
The central challenge the researchers aimed to solve was the instability of organic materials, such as polymers and small molecules, when exposed to water, and the inefficiencies caused by energy losses at critical interfaces. To address this, the team devised a multi-layer device architecture incorporating a protected organic photoactive layer and a graphite sheet functionalised with a nickel-iron catalyst. By preventing water-induced degradation, they achieved high photocurrent densities and device durability surpassing previous systems in the field.
“Our work demonstrates that high-performance, stable solar water splitting can be achieved using low-cost, scalable organic materials,” said Dr Flurin Eisner, Lecturer in Green Energy at Queen Mary University of London, who led the development of the organic photoactive layers.
“Organic materials are highly tunable in terms of their properties, such as the light they absorb and their electrical properties, which means they can be an extremely versatile platform on which to build various ways to convert sunlight into fuels (such as hydrogen) or even chemicals, emulating natural photosynthesis in plants. This opens exciting new avenues for sustainable fuels and chemicals production.”
By combining a bulk heterojunction photoactive layer with the protective graphite sheet, the device demonstrated a photocurrent density of over 25 mA cm⁻² at +1.23 V vs. the reversible hydrogen electrode for solar-driven water oxidation – substantially improving upon previous efforts. Crucially, it also showcased operational stability over several days, supporting the possibility of real-world applications.
“Beyond the record efficiency and stability of our organic devices, our results disentangle the contribution of the different components in the device degradation, which has been a significant challenge of the field,” said Dr Matyas Daboczi, first author of the study at Imperial’s Department of Chemical Engineering (now Marie Skłodowska-Curie Research Fellow at the HUN-REN Centre for Energy Research and a Visiting Researcher in the Department of Chemical Engineering at Imperial).
“I believe that our insights and guidelines will be valuable for further improving the stability and performance of such organic photoelectrochemical devices towards real-world application.”
The team also successfully demonstrated full water splitting devices capable of generating hydrogen from water and sunlight, without the need for external electricity. These systems reached a solar-to-hydrogen efficiency of 5%, marking a notable milestone for technologies like off-grid hydrogen production.
“This result is a significant improvement in organic photoelectrochemical device performance, achieving record solar-to-hydrogen efficiencies,” commented Dr Salvador Eslava, lead academic of the study at Imperial’s Department of Chemical Engineering. “
The approach leverages the advantages of organic bulk heterojunctions, which offer impressive photocurrents, photovoltages, abundant elements, and ease of processing, and applies them to the electrodes of photoelectrochemical cells.”
Looking to the future, the team plans to focus on improving material stability and scaling up the technology for industrial applications. They hope that this new blueprint will encourage wider adoption of hydrogen as a clean energy carrier.
