Intercalation and Encapsulation of In Situ Grown Black Phosphorus within Ti3C2Tx MXene Sheets for Energy Storage

An innovative yet simple approach for the in situ growth of black phosphorus (BP) over MXene sheets has been carried out by a facile and simple hydrothermal treatment. Basically, a dual strategy is adopted to expand MXene interlayer spacing by in situ intercalation of BP along with encapsulation with an antioxidant agent to prevent oxidation at elevated temperatures. Detailed nucleation and growth mechanisms are explained by optimizing the ratio of BP in MXene–BP hybrid material supported by XRD, FE-SEM, FT-IR, Raman spectroscopy, and XPS characterizations. The presence of surface terminations (−OH, −O) at enlarged interlayers of MXenes chemically attached to BP causes the production of Ti–O–P linkages at the junctions of heterostructures, resulting in uniform in situ development of BP over MXenes nanolayers. These interactions enhance the Coulombic reactions between the core and valence states present at the interface (Ti–O–P) bonds, which is beneficial for large electronic transfers. Further, the optimized MXene–BP (10 mg) hybrid denoted as the MX–BP-10 sample was analyzed systematically with temperature-dependent Raman spectroscopy at elevated temperatures to check its stability at high temperatures. Moreover, a symmetric MX–BP-10 hybrid supercapacitor device was fabricated, which reveals excellent specific capacitance of 120 mF/cm2 at a current density of 0.4 mA/cm2 with an exceptional capacitance retention of 95% and Coulombic efficiency of 92% even after 10 000 charge–discharge cycles. This unique intercalation and encapsulation approach to passivate MXenes gives multidimensional insights to tune its electrochemical properties at high temperature so as to enhance its oxidation resistance.