Mixed Nanosheets Research Articles

Irradiated rGO electrode-based high-performance supercapacitors: Boosting effect of GO/rGO mixed nanosheets on electrochemical performance

Supercapacitors are seemed to be one of the most promising choices as an energy storage system. However, there is still a gap in enhancing its energy density values and cyclic stabilities throughout a facile approach. Herein, it was aimed to propose a facile and effective way to fabricate high-energy supercapacitor electrode material based on reduced graphene oxide (rGO) nanostructure. Bearing this in mind, the bulk rGO powder was irradiated by various beam sources including Co-60, Am-241, Na-22, and Sr-90, and the resultant irradiated rGO samples were utilized as the electrode active material to fabricate symmetrical supercapacitor cells. The irradiated rGO samples were characterized both physicochemically and electrochemically. The physicochemical characterizations revealed that as a consequence of the irradiation, both GO and rGO nanosheets were formed in the resultant powder and the d-spacing of the graphene nanosheets were expanded. The highest electrochemical performance metrics were acquired for Sr-90 irradiated rGO electrode-based supercapacitor cell with the specific capacitance value of 585.44F.g−1 at 0.2 A.g−1, and outstanding capacitance retention performance of 97.14% for the 5000th CV cycles at 200 mV.s−1. Moreover, the energy density and power density values were comparable to other commercial energy storage systems such as lead-acid and nickel-metal hybrid batteries. Hence, it can be speculated that these pioneering breakthroughs could pave the way for cutting-edge high-energy supercapacitors based on rGO-derivatives with superior electrochemical performance metrics, as well as engineering of high-performance rGO-based materials to be employed in various energy applications.

Van der Waals type II carbon nitride homojunctions for visible light photocatalytic hydrogen evolution

Photocatalytic hydrogen evolution reaction (PC-HER) provides a solution to energy crisis and environmental pollution. Herein, different graphitic carbon nitride (g-C3N4)-based van der Waals (vdW) type II homojunctions have been fabricated and g-C3N4/K-doped g-C3N4 nanosheets have an outstanding PC-HER rate of 1,243 µmol-h−1·g−1 under visible light, higher than that of bulk g-C3N4, doped g-C3N4 nanosheets, and mixed nanosheets. The enhanced PC-HER performance can be ascribed to the cooperative effects of the shortened bandgap, enlarged specific surface area, matched type II energy band structure, “face to face” vdW charge interaction, and peculiarly partite positions of the conduction and valence bands in different layers. Besides, the type II junctions were found superior to binary type II junction. This study highlights the synergistic effect of different strategies in improving the PC-HER capacities of g-C3N4, especially the application of particular vdW junctions, and provides new insights to the structures and mechanism.