Highly sensitive and selective visual hydrogen detectors based on YxMg1−x thin films

We demonstrate how thin films of Y-Mg based alloys capped with a catalytic Pd layer can be used as an inexpensive device to visualize the presence of hydrogen at different concentrations. Using the change in the intrinsic optical properties of Y-Mg alloys upon exposure to hydrogen, combined with an interference effect due to a Pd cap layer, we obtain a device that can indicate the presence of hydrogen at concentrations as low as 20 ppm just by a reversible change in color. The eye-visible color change circumvents the use of any electronics in this device, thereby making it an inexpensive H2 detector. The detector shows high selectivity towards H2 in H2-O2-mixtures, and can respond within 20 s to 0.25% H2 in the presence of 18% O2. Therefore the device has the potential to be used in applications where hydrogen needs to be detected in the presence of oxygen. We show how the Mg concentration in the alloy influences the color change and the detector's response kinetics.