Functional Nanomaterials Based Electrochemical and Chemiresistive Sensors for Hydrogen Detection: A Review

Hydrogen is a lightweight, small molecule that is highly flammable and causes an explosion when exposed to air by >4%. It is a colorless and odorless gas; hence, its physical examination is challenging. Therefore, a reliable detection tool is highly demanded to avoid the risk associated with their explosion. Nonetheless, hydrogen sensing is a difficult task that needs a sensitive sensor. Metal nanoparticles (MNPs) and two-dimensional (2D) nanomaterials-based sensors have gained remarkable attention for hydrogen detection. They offer excellent properties such as high active surface area, active sites, porosity, and long-term stability, which make them promising materials for sensor applications. Moreover, a sheet-like structure and flat surface favors a fast adsorption and desorption process. Therefore, the sensing performance of the sensor notably improved. This review deals with the MNPs and 2D nanomaterials such as metal oxides and sulfides, graphene, MXene, metal-organic framework, and polymeric hybrid nanocomposite-based electrochemical and chemiresistive sensors for hydrogen detection. Furthermore, the insight into the mechanistic approaches for hydrogen sensing has been discussed. Lastly, the challenges associated with hydrogen detection, their future advancements, and their commercial perspective have been addressed.