Palladium-based Nanoplasmonics for Ultrafast and Deactivation-Resistant Hydrogen Detection

Licentiate thesis, 2019

In the hydrogen economy scenario, hHydrogen gas is ispotential to be the main energy carrier in the hydrogen economy scenario in the upcoming future. It receives much attention since the reaction with oxygen generates electricity and produces only clean waterhydrogen is attractive as energy carrier since the energy produced by its reaction with oxygen only producesleaves water as by-product. However,  hHydrogen , however, is flammable when mixed within ambient air even at low concentration, i.e. above 4 vol.%. Therefore, safety systems areis mandatory to monitor and prevent any leaks. The However, existing hydrogen sensor technology today, unfortunately, has not been able to passdoes not meet the stringent future safetyperformance targets for safety sensors standard.

Motivated by thise safety issuefactat, in this thesis we I exploit the localized surface plasmon resonance (LSPR) of palladium (Pd)Pd and Pd-alloy nanoparticles to buildin the quest to develop next generation optical based hydrogen sensors. The uUnique features of an optical sensor among with respect to the other types are the inherent free-of-spark-free operation (thus safer), the possibility to perform a remote readout by light and the possibility forof a multiplexing. Specifically, I PalladiumPd, however, has limitations which hinders the hydrogen sensor to meet the requirement.

My thesis reportsIn this thesis I focus onreport two key aspects related to the hydrogen sensor challenge: (i) the  development of the palladiumPd-alloy based nanoplasmonic sensors that are both deactivation resistant and meet the stringent response time target, and (ii) the fundamental studies onunderstanding of nanoparticle-hydrogen interactions in the presence of different coatings. the hydrogen-palladiumPd nanoparticle

As the key results, I have developed two different types of plasmonic hydrogen sensor platforms either based on a PdAuCu ternary alloy or utilizing thin polymer film coatings. They exhibit exceptional deactivation resistance towards poisoning gases like carbon monoxide or nitrogen dioxide, and they meet the most stringent sensor response time target defined by the US Department of Energy. Furthermore, I have devised generic design rules for the optimization of plasmonic hydrogen sensor detection limits based on fundamental understanding, and systematically characterized the impact of surfactant molecules widely used in colloidal synthesis of Pd nanocrystals on their interaction with hydrogen gas. All in all, . The former implementation aspect includes two different strategies to optimize the sensor: (i) Au and Cu alloying and (ii) polymer (PMMA, PTFE) coating. The later fundamental aspect covers two studies on: (i) the correlation between the absorbed hydrogen and the optical response correlation and (ii) the (de)hydrogenation of surfactant/stabilizer-coated nanoparticle.

Finally, weWe  managed to achieve excellent hydrogen sensor performance that meets the strict demand and we acquired deeper insight on the hydrogen sensing mechanism which is important for the sensor design. tThese findings hopefully contribute to the safety aspect ofa safer hydrogen economy safety aspect and enable wider applicationsin the future.