# A Palladium-Deposited Molybdenum Disulfide-Based Hydrogen Sensor at Room Temperature
## 1 Introduction  
Recently, global interest in eco-friendly energy sources has increased in response to pressing concerns about climate change and the depletion of fossil fuels. Among new sustainable energy options, H\({}_{2}\) energy has received considerable attention. H\({}_{2}\) is an eco-friendly, energy-efficient, and richly available energy source and has the potential to be a key competitor in the pursuit of sustainable power generation. However, the remarkable potential of H\({}_{2}\) energy is coupled with the inherent challenge of requiring innovative solutions. One of the significant challenges associated with H\({}_{2}\) is its unique properties. H\({}_{2}\) is a colorless, odorless, and tasteless gas that is seemingly harmless but can be highly flammable and explosive if the concentration in the surrounding air exceeds 4% [1]. This property poses a significant safety risk, especially in industries where H\({}_{2}\) is an important component. To reduce the potential risks and protect both people and infrastructure, the timely detection of H\({}_{2}\) leaks is essential. For this reason, hydrogen sensors have become an integral part of various industries that rely on H\({}_{2}\). Hydrogen sensors play a pivotal role in ensuring safety by accurately detecting H\({}_{2}\) leaks early on. For practical applications in a variety of industrial environments, hydrogen sensors must satisfy the criteria of being cost-effective, compact, energy-efficient, and have high-performance results. The hydrogen sensors available in the market are typically categorized into several types, including electrochemical sensors, catalyst-based sensors, work function-based sensors, and resistive-based sensors. Among them, electrochemical and chemiresistivehydrogen sensors are attracting attention for being commercially available sensors. Electrochemical sensors are sensitive, selective, and have a low limit of detection (LOD); however, they are highly sensitive to ambient conditions and require high manufacturing costs. On the other hand, chemiresistive sensors have advantages, such as efficient sensing performance, low-cost manufacturing, and low power. Among the chemiresistive sensors, Pd-based resistive sensors and semiconducting metal oxide (SMO)-based sensors are being actively studied. Pd-based resistive sensors provide simplicity, high reactivity to H\({}_{2}\), and detection at room temperature but reduce the detection performance in ambient air. SMO-based sensors have been commercialized due to their effectiveness and high compatibility with H\({}_{2}\) detection. The SMO-based sensor has a high operating temperature. High operating temperatures not only increase power consumption but also increase the combustibility of H\({}_{2}\), which creates a risk of explosion [2; 3; 4]. The recent rapid development of sensor technology has revealed many application methods. In particular, nanowire structures are attracting attention as one of the most promising methods thanks to their excellent reactivity and proficiency in detection. Among these developments, research by [PERSON] et al. deserves to be noted. Their exploration of the utilization of Pd/SnO\({}_{2}\) nanowire structures showed remarkable reactivity to hydrogen. However, an important consideration is the operating requirement of relatively high temperatures, especially at about 150 \({}^{\circ}\)C [5]. Therefore, the development of reliable hydrogen sensors that can operate at room temperature is the most important factor. Previous researchers were interested in two-dimensional (2D) materials, which are now attracting attention in various scientific fields due to their unique structural, electronic, and mechanical properties. Graphene, in particular, is a subject of extensive research due to graphene's excellent properties within the domain of 2D materials. However, the application of graphene as a sensor is limited in certain situations due to the difficulty in controlling its band gap [6].