<p>Early transition metal carbides and/or nitrides form Nb (niobium)-based MXenes, which are now among the most versatile two-dimensional materials. In a variety of scientific applications, such as sensors and energy storage, MXenes have gained popularity due to their high metallic conductivity, tunable surface chemistry, rich surface functional groups, large specific surface area, layered structure, good redox capabilities, hydrophilicity, high energy storage ability, layered structure for ion intercalations, and other exceptional properties. This paper examines the latest developments of Nb-based MXenes in gas sensors and supercapacitors (SCs), applying the different synthesis methods and properties of MXenes. Furthermore, this paper highlights how MXenes' exceptional properties have driven their growing popularity across a range of scientific applications, including energy storage devices and sensor design. The different MXenes-based electrodes as a part of SCs and gas sensors are also highlighted in this review with a focus on their practical applications and capacitive properties such as specific capacitance, cyclic stability, energy and power densities, and other gas sensing performance features like temperature, response rate, and recovery rate at different humidities.</p> Graphical Abstract <p></p>