Facile solid-state synthesis of layered molybdenum boride-based electrode for efficient electrochemical aqueous asymmetric supercapacitor.

• Facile, solid-state, low temperature synthesized layered molybdenum boride found out to be of thin nanosheets. • MoB are found to be electrochemically active in acid and neutral electrolyte, where the nanosheets provide a higher surface area for the electrolyte ion interaction. • MoB was directly employed as a negative electrode, against the activated carbon as a positive electrode for the asymmetric supercapacitors. • The device was found to deliver a high energy density and power density with long-term stability in charge/discharge cyclings. • Interestingly, it was discovered that the outcomes of the electrochemical performance of asymmetric supercapacitors could be tuned by the electrolyte. [Display omitted] The survey of 2D materials has triggered the energy storage and conversion research. In molybdenum-based 2D layered materials are of great significance, due to their remarkable properties. In this work, simple solid-state synthesis and formation of molybdenum boride has been explored with various characteristic techniques. The advanced characterization techniques like XRD, TEM, XPS, BET, have been used to understand the crystallinity, morphology, and surface area of the layered MoB (LMB). The electrochemical performances of LMB electrode were verified with different aqueous electrolytes. The LMB electrode has been found to store higher charge in H 2 SO 4 than Na 2 SO 4 electrolyte. The LMB electrode delivered a specific capacitance of 445 F g−1 in H 2 SO 4 where 130 F g−1 in Na 2 SO 4 at a current density of 1 A g−1. Such behavior may be due to ionic size and mobility of ions in the electrolyte. The asymmetric supercapacitors have been fabricated with LMB and activated carbon (AC) electrode then the device performance was examined in both the electrolyte. On optimization, it was found the device works well in potential window 1.4 V in H 2 SO 4 while the potential window was extended to 1.8 V in Na 2 SO 4 electrolyte. The device was found to deliver an energy density of 14 W h kg−1 at a power density of 16.8 kW kg−1 for H 2 SO 4 with a better capacity retention of 98% for 2000 cycles. Thus, LMB electrode in supercapacitor application has been demonstrated for the first time, which can instigate more investigations for layered molybdenum-based electrodes for energy storage devices. [ABSTRACT FROM AUTHOR]