Introduction: Hydrogen Energy and the Need for Detection
What is Hydrogen Energy? Hydrogen has become central to the energy sector. Standard fossil fuels, combined with their inherent polluting qualities, are wholly unsustainable and at the current rate of consumption will eventually run out altogether. Hydrogen energy has almost zero harmful emissions. However, hydrogen is not naturally occurring in a usable form for energy storage technology. It must be produced by chemical processes, giving rise to financial, technical and safety concerns. The demand for hydrogen as an energy source is expected to increase by more than seven times by 2040.
How is it made? Hydrogen can be produced using fossil fuels, conventional sources or via renewable energy sources. The most widely adopted technique is steam reforming, where hydrogen atoms are separated from methane. Electrolysis, whereby a direct current is applied to water to release the constituent hydrogen and oxygen. Another major technology involves using proton exchange membranes (PEMs), which are utilised efficiently in electrolysers to produce hydrogen. Photolysis of water, where water molecules absorb energy at around 285.57 kJ/mole using ultraviolet radiations. The breaking of H-O bonds via this method releases hydrogen in the presence of catalysts, such as tin oxide and sulphur oxides.
More recently, biomass has emerged as a more promising alternative to fossil fuels for hydrogen production due to its abundant reserves, ease of oxidation, and high annual output. Various biomass-based methods for hydrogen production include the thermochemical conversion of wood waste, waste treatment processes, and fermentation of microalgae and cassava. Both biological and thermochemical approaches effectively produce hydrogen while minimizing harmful emissions and waste, making them environmentally friendly options for sustainable hydrogen production.
A robust organic hydrogen sensor for distributed monitoring applications
Hydrogen is an abundant and clean energy source that could help to decarbonise difficult-to-electrify economic sectors, such as domestic and commercial travel. However, its safe deployment relies on the availability of cost-effective hydrogen detection technologies. This is what the collaborators have achieved with outstanding results.
A hydrogen sensor that uses an organic semiconductor as the active layer is the core concept of the investigation; operating over a wide temperature and humidity range. Reliable and rapid hydrogen detection is obtained via a process known as p-doping, whereby atmospheric oxygen acts as a dopant to the organic semiconductor, improving conductivity. In the presence of hydrogen, this process is reversed and results in a sudden drop in current. The sensor exhibits a high responsivity (more than 10,000), fast response time (less than 1 s), low limit of detection (around 192 ppb) and low power consumption (less than 2 μW). It can operate continuously for more than 646 days in ambient air at room temperature.
Courtesy of Nature
Courtesy of Nature
The unique properties of diatomic hydrogen (H2), such as its rapid diffusion rate and high energy density, make it suitable for various applications in different industries; including energy, transportation, petroleum refining, defence, space, food and pharmaceuticals. However, its combustible nature, low flammability point (approximately 4 vol% H2 in the air) and the inability of people to detect it using their senses create safety concerns for hydrogen production, storage and usage. There is a growing demand for sensitive and selective hydrogen sensors that can provide an early warning of potential leaks. To meet the large volume demands of the emerging hydrogen economies, such sensors must be cost-effective to manufacture, consume little power, operate at ambient conditions and have a minimal environmental impact.
Previous attempts exploring hydrogen sensors has offered a variety of active elements and materials. These have included noble metals such as palladium (Pd) and oxide materials such as zinc oxide (ZnO), molybdenum trioxide (MoO3), titanium dioxide (TiO2), niobium pentoxide (Nb2O5), tin(IV) oxide (SnO2), tungsten oxide (W2O3) and indium(III) oxide (In2O3). However, low responsivity and high running temperature make them less suitable for this application.
Various metal composites and organic materials, such as polypyrrole nanofibres and polyaniline, have also been investigated for H2 detection. These materials come with their own set of disadvantages, mainly slow response time. Time of course being imperative when referring to potential leaks of volatile substances.
The principal investigators describe a hydrogen sensor that uses an organic semiconductor as the active layer. The current changes as a result of the interaction between hydrogen and the physisorbed oxygen species. Consequently, the sensor offers high responsivity, low power consumption, low detection limit and good stability in harsh testing conditions. This myriad of traits make organic semiconductors essential components in hydrogen detection and act to alleviate the safety concerns around hydrogen as a potential fuel source of the future.
Full Article
Mandal, S., Marsh, A.V., Faber, H. et al. A robust organic hydrogen sensor for distributed monitoring applications. Nat Electron (2025). https://doi.org/10.1038/s41928-025-01352-y
The aforementioned paper was a collaborative effort of multiple authors, across a range of institutions; including King Abdullah University of Science and Technology (KAUST), Saudi Arabia, Indian Institute of Technology Kharagpur, India, National Technical University of Athens, Greece and The University of Manchester, UK.