Researchers at the University of California – San Diego report the use of molybdenum disulfide–palladium composites for highly sensitive detection of hydrogen at room temperature. Particular applications of this technology are in detection of H₂ leaks from fuel cells, from which there can be serious safety concerns. Metal oxide sensors are often used, but they have a high operating temperature. Sensors that operate at room-temperature would be highly beneficial.

In the work by Professor Sungho Jin and co-workers, a solution-processed MoS₂ nanosheet–palladium nanoparticle composite is presented – this composite shows a remarkable electrical response toward hydrogen with excellent response and recovery time.

The composite is prepared by drop-casting of MoS₂–PdCl₂ solution in SiO₂-coated silicon substrates, followed by annealing to reduce the PdCl₂. This method produces highly exfoliated MoS₂ nanosheets.

The role of palladium in the composite is critical as MoS₂ nanosheets alone do not show any significant response to H₂ exposure, whereas the composite shows a strong response to 50000 ppm H₂. The response to H₂ is characterized by a sharp decrease of resistance followed by saturation, and there is complete recovery in air without any heating or UV irradiation. Device response and recovery times were 40 and 83 s respectively. Furthermore, cross-sensitivity to ammonia, acetone, and ethanol is also shown to be minimal, and the device outperforms other candidate devices made from graphene–palladium composite films.

The mechanism for H₂ sensing is proposed.

All in all, these results demonstrate the great potential of these systems in the inexpensive and scalable fabrication of high-sensitivity chemical sensors.

Advanced Science is a new journal from the team behind Advanced Materials, Advanced Functional Materials, and Small. The journal is fully Open Access and is free to read now at www.advancedscience.com.