Nanoparticle based hydrogen sensing for both high and low concentration applications
Examensarbete för masterexamen
The hydrogen economy is the vision of a sustainable society where hydrogen is used as fuel for vehicles, heat generation and energy storage, with water as the only byproduct. To realize this vision, issues such as fuel cell efficiency and safety must be handled. Therefore, hydrogen sensors both for leak detection and fuel cell monitoring are needed. Palladium is known to have a high selectivity in room temperature towards hydrogen gas, it is (especially in alloys) a promising candidate for this application. This study presents an investigation of several Pd alloy nanoplasmonic hydrogen sensors. Nickel and copper are metals of comparatively small lattice constants which increase the high concentration sensitivity of pure Pd. Silver has a comparatively large lattice constant and an ability to remove the effect of hysteresis which is also firmly connected with pure Pd. The Pd alloys of composition Pd80Ag20 and Pd70Ag30 both showed large sensitivities in the 0.5-5 % H2 region but a high limit of detection of 0.20 % for Pd80Ag20 and 0.38 % for Pd70Ag30. The kinetics of the alloys were slow with 138 s to 90 % response for Pd80Ag20 at 0.9 % H2 versus 270 s for Pd70Ag30. The alloy compositions Pd85Ni15 and Pd70Cu30 resulted in sensors with linear response in the 5-95 % H2 region with sensitivities 0.026 nm/% and 0.035 nm/% respectively. They had a limit of detection estimated to 0.71 % and 0.41 % and a precision of 2.8 % and 1.7 %. The linear response in the high concentration region indicates that both PdNi and PdCu are well suited for fuel cell hydrogen sensing.