Chemiresistive Hydrogen Sensors: Fundamentals, Recent Advances, and Challenges

Abstract

Hydrogen (H 2 ) is one of the next-generation energy sources because it is abundant in nature and has a high combustion efficiency that produces environmentally benign products (H 2 O). However, H 2 /air mixtures are explosive at H 2 concentrations above 4%, thus any leakage of H 2 must be rapidly and reliably detected at much lower concentrations to ensure safety. Among the various types of H 2 sensors, chemiresistive sensors are one of the most promising sensing systems due to their simplicity and low cost. This review highlights the advances in H 2 chemiresistors, including metal-, semiconducting metal oxide-, carbon-based materials, and other materials. The underlying sensing mechanisms for different types of materials are discussed, and the correlation of sensing performances with nanostructures, surface chemistry, and electronic properties is presented. In addition, the discussion of each material emphasizes key advances and strategies to develop superior H 2 sensors. Furthermore, recent key advances in other types of H 2 sensors are briefly discussed. Finally, the review concludes with a brief outlook, perspective, and future directions.

Grain-growth mediated hydrogen sorption kinetics and compensation effect in single Pd nanoparticles

“…Therefore, the understanding of the influence of grain boundaries on kinetic processes, for example during nanoscale phase transformations, is widely lacking. This is problematic since phase transformations in nanostructured materials are a central concept in energy storage technologies like batteries 15 , 16 and hydrides 17 , in hydrogen sensors 18 , 19 , as well as in heterogeneous catalysis, for example in situations with metal catalyst oxidation 20 – 22 .…”

Tantalum‐Palladium: Hysteresis‐Free Optical Hydrogen Sensor Over 7 Orders of Magnitude in Pressure with Sub‐Second Response

“…Optical metal‐hydride hydrogen sensors are an attractive candidate for large‐scale implementation in the future hydrogen economy. [ 8–12 ] Their working principle is based on the fact that the optical properties change when metal hydrides partly hydrogenate when they are exposed to a hydrogen atmosphere. These changes are probed by for example measuring the fraction of transmitted or reflected light or the frequency shift of the (localized) surface plasmon resonance peak and from one of these optical signals the partial hydrogen pressure P H 2 can be determined.…”

“…Compared to conventional ways of detecting hydrogen such as catalytic resistor detectors and electrochemical devices, optical fiber hydrogen sensors are inherently safe and can be made small and inexpensive. [ 8,9,11–18 ]…”

Grain-Growth Mediated Hydrogen Sorption Kinetics and Compensation Effect in Single Pd Nanoparticles

“…[6][7][8][9][10][11][12][13][14] Therefore, the understanding of the influence of grain boundaries on kinetic processes, for example during nanoscale phase transformations, is widely lacking. This is problematic since phase transformations in nanostructured materials are a central concept in energy storage technologies like batteries 15,16 and hydrides 17 , in hydrogen sensors 18,19 , as well as in heterogeneous catalysis, for example through metal catalyst oxidation. [20][21][22] To overcome this current lack of understanding, single particle experiments hold the key since they have been successfully deployed to investigate the impact of nanostructure dimensions and geometry on the thermodynamics of phase transformation processes, where they have focused on hysteresis effects 7,8,11 and the role of defects like dislocations and voids 9,10,12 .…”