Widespread application of hydrogen for energy storage, manufacturing processes, medical treatment, and other uses has motivated development in hydrogen sensing technology for safety and control.Hydrogen sensors have been well studied and commercialized yet face increasing demand for lower cost, broader operating conditions, and especially smaller scale. Two-dimensional (2D) materials have gained prominence due to atom-scale thicknesses and special structure which give rise to unique electrical and mechanical properties in combination with the potential for submicron miniaturization of sensing devices. These characteristics pose a high potential for gas detection in general and for hydrogen detection in particular. This paper reviews hydrogen sensors utilizing 2D materials in order to provide insight into current sensing technologies and opportunities for future hydrogen detection devices.

The study of gas adsorption on a solid surface evaluates the affinity between sorbate gas and sorbent substrate and factors that contribute to this. This paper presents a test platform for adsorption experiments of various gases on various solid surfaces. Controlled environmental conditions enable investigations in materials surface science and increase the consistency among adsorption data. The system utilizes a quartz crystal microbalance to perform gravimetric analysis of deposition and adsorption, enabling investigation of the interaction of gaseous molecules with solid surfaces. In this study, a quartz crystal microbalance as gas adsorption detector was integrated with an environmental chamber to create a versatile tool for gas adsorption experiments on thin films. Experimental operation of this apparatus was demonstrated via acquisition of the adsorption isotherms of cyclohexane vapor on a gold surface at 55 and 70 °C. The result indicated International Union of Pure and Applied Chemistry Type II adsorption. Consequentially, application of the Brunauer–Emmett–Teller model to the isotherm data subject to predefined criteria for linear region selection yielded a surface area of the sorbent of 0.53 cm2 at 55 °C. From the monolayer region of the isotherms, the isosteric heat of adsorption of the cyclohexane vapor on gold was calculated to be 37 kJ mol−1.

Magnesium diboride (MgB 2 ) has demonstrated, theoretically and experimentally, promise as a candidate material for hydrogen storage and has thus attracted much contemporary research interest. To study hydrogen gas adsorption on MgB 2 thin films using a quartz crystal microbalance (QCM)�a workhorse apparatus for this specific experiment�MgB 2 must be deposited uniformly on the active surface of the QCM without damaging the quartz's performance. In work presented here, a wet-chemistry colloid synthesis and deposition process of a MgB 2 thin film on a gold (Au) surface was established to avoid the extreme conditions of conventional physical deposition methods. This process also counteracts the unwanted phenomena of drying droplets on a solid surface, particularly the coffee-ring effect. To verify the normal function of the QCM after MgB 2 deposition and its ability to obtain meaningful data, simple gas adsorption tests were conducted on the QCM, and the MgB 2 film on the QCM was characterized with X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) for elemental analysis and surface roughness, respectively. To obtain information about the thickness and the involvement of the coffee-ring effect, the same synthesis route was applied on a similar gold substrate�an evaporated Au film on glass. XPS characterization of the film and its precursor suspension shows the potential existence of both MgB 2 and its oxide forms. The film's thickness on evaporated Au was measured by scanning transmission electron microscopy (STEM) to be 3.9 nm. The resulting samples show mitigation of the coffeering effect through roughness measurements with AFM at two scan sizes of 50 × 50 and 1 × 1 μm 2 .

Hydrogen storage material is a crucial research topic for future energy utilization employing hydrogen and among those of interest, magnesium diboride (MgB2) has shown its prevalence. In this study, a...