• Energy Research

We have effectively synthesized ZnS, FeSe2, and their nanocomposite using a straightforward and affordable solvothermal process. We also investigated for the first time their ideal electrochemical performance for supercapacitors. The ZnS and FeSe2 positive electrodes exhibit capacitances of 266.2 F g−1 and 294.3 F g−1, respectively, with fascinating nanostructures and morphology. Their respective nanocomposites, AZ-1, AZ-2, and AZ-3, deliver capacitances of 356.8, 444.4, and 326.1 F g−1 with significant rate performance in aqueous solution in a three-electrode assembly. The lowest ESR and Rct values of AZ-2 electrodes, which improved conductivity and charge transport kinetics and created a synergistic effect between ZnS and FeSe2 electrodes, are responsible for their exceptional capacitative performance. We built an asymmetric supercapacitor (AZ-2/AC) with an optimal voltage of 1.6 V, which demonstrated great power density (6250 W kg−1) and energy density (33 Wh kg−1) with remarkable cycling stability (88.1%) in an aqueous electrolyte after 12,000 cycles. As a result, FeSe2-based nanocomposites are strong contenders for realizing high energy and power delivery for practical applications.

Abstract Light induced deposition of metallic Zn, Fe, Co, Ni, Bi, and Cu on crystalline Si solar cell cathodes has been studied as a part of developing self-powered devices. The direct metal deposition relies on the relative position of Si Fermi level and the equilibrium potential of the metal/ion and H+/H2 in electrolyte. Direct deposition of above mentioned metals shows three types of light-induced plating (LIP) behavior. Even with a relative large potential barrier, Cu2+/Cu and Bi3+/Bi could be deposited by the induced plating of the hydrogen evolution. The current density of the Co2+/Co and Ni2+/Ni have been reduced by the light absorption of the electrolyte impact on the solar cell. This work demonstrated the Si solar cells can be used to provide self-powered for metal deposition which can be used in the heavy metal treatment for the polluted water.

A high capacitance and widened voltage frames for an aqueous supercapacitor system are challenging to realize simultaneously in an aqueous medium. The severe water splitting seriously restricts the narrow voltage of the aqueous electrolyte beyond 2 V. To overcome this limitation, herein, we proposed the facile wet-chemical synthesis of a new CuSe-TiO2-GO ternary nanocomposite for hybrid supercapacitors, thus boosting the specific energy up to some maximum extent. The capacitive charge storage mechanism of the CuSe-TiO2-GO ternary nanocomposite electrode was tested in an aqueous solution with 3 M KOH as the electrolyte in a three-cell mode assembly. The voltammogram analysis manifests good reversibility and a remarkable capacitive response at various currents and sweep rates, with a durable rate capability. At the same time, the discharge/charge platforms realize the most significant capacitance and a capacity of 920 F/g (153 mAh/g), supported by the impedance analysis with minimal resistances, ensuring the supply of electrolyte ion diffusion to the active host electrode interface. The built 2 V CuSe-TiO2-GO||AC-GO||KOH hybrid supercapacitor accomplished a significant capacitance of 175 F/g, high specific energy of 36 Wh/kg, superior specific power of 4781 W/kg, and extraordinary stability of 91.3% retention relative to the stable cycling performance. These merits pave a new way to build other ternary nanocomposites to achieve superior performance for energy storage devices.