Concerted effect from the interaction of zero-dimensional dual quantum dots with two-dimensional graphene matrix for energy conversion and storage applications

Several research in the field of energy conversion and storage has been sparked by the development of composite electrode materials displaying tremendous energy and power densities. By employing liquid exfoliation followed by the solvothermal approach, we have successfully designed nitrogen-doped carbon dots (CDs) and hematite dots (HtDs) functionalized reduced graphene (RG) hybrid ternary composites (RG@CDs/HtDs). The hybrid electrode material, RG@CDs/HtDs, has superior electrochemical nitrogen reduction activity and has remarkable supercapacitor activity with outstanding stability up to 10,000 cycles, a high specific capacitance of 1566f/g at scan rate of 2 mvs-1. DFT calculation revealed the higher charge storage is a result of the improved quantum capacitance and intense electronic states for the ternary structure RG@CDs/HtDs near the Fermi level. Using Mn₃O₄/C as the anode and RG@CDs/HtDs as the cathode, an asymmetric aqueous supercapacitor device has been assembled which surprisingly operates in a stable and wide potential window of 2.5 v with an ultra-high energy density (134whkg^-1) along with extraordinary rate capability and is stable at 10,000 cycles, which was verified by powering a red LED. (author)