The versatile, and tunable surface chemistry of two-dimensional (2D) MXenes coupled with their distinct properties including hydrophilic nature, favorable ion transport and metallic conductivity make them an ideal candidate for energy storage devices. Modifying surface terminations by doping heteroatom is an efficient approach to improve layer spacing and electrochemical active sites of the MXenes. However, nitrogen doping in 2D materials has been an effective way to enhance their electrochemical characteristics. In this study, N-Nb₂CT_x MXene was synthesized by utilizing the hydrothermal method in which nitrogen doping in MXene was confirmed through several characterization techniques. Tuning of MXene surface by a cost-effective strategy has shown improved performance for energy storage. After doping nitrogen in Nb₂CT_x MXene, it has shown enhanced pseudocapacitance performance in 1 M potassium hydroxide (KOH), elevating the electrochemical properties. N-Nb₂CT_x MXene has displayed a better specific capacitance of up to 640 F·g^–1 while pristine Nb₂CT_x MXene has shown 276 F·g^–1 from the cyclic voltammogram (CV) at a scan rate of 5 mV·s^–1. In addition, an asymmetric device of activated carbon/N-Nb₂CT_x was assembled for real-world applications, it has exhibited refined results. The asymmetric device has shown remarkable cyclic stability of 90% capacity retention at a current density of 5 A·g^–1 for 5000 cycles. Additionally, the detailed density functional theory (DFT) calculations support the stability of nitrogen replacing the fluorine functional group, complementing the experiment.

MXenes are fast-growing two-dimensional (2D) carbides, nitrides, and carbonitrides nanomaterials exhibiting combined special features of high electronic conductivity, optoelectronic properties, and electrochemical properties with hydrophilicity character. The plasmonic characteristics of MXenes with optical nonlinearities associated with ultrafast dynamics empower it as one of the strongest candidates for transparent optoelectronic applications in the field of energy storage, conversion, photodetectors, quantum dot light-emitting diodes, smart windows, environmentally. It is timely to introduce and summarize a review article dedicated to the transparent MXene-based multifunctional applications that provide well-designed future roadmaps for these significant MXene smart materials. This review comprehensively discusses the transparent MXenes towards transparent electrodes for supercapacitors and beyond. The importance of MXene optoelectronic properties and tunability via composite materials incorporated with different polymers, oxides, sulfides, and carbonaceous nanomaterials are also thoroughly reviewed.

The effect of twist angle on the hydrogenation of bilayer graphene (BLG) is systematically explored by density functional theory (DFT) calculations. We found that a twist between the upper and lower layers of the graphene BLGs, either big or small, interferes with the formation of inter-layer C–C covalent bonds and this leads to strong resistance to hydrogenation. In addition, the electronic properties of stable, hydrogenated twisted BLG with different twist angles and degrees of H coverage were investigated. This study paves the way to the selective functionalization of BLG for various applications.