RESUMEN
Transition metal sulfides and selenides are common electrode materials in supercapacitors. However, the slow redox kinetics and structural collapse during charge-discharge cycles of single-component materials have impeded their electrochemical performance. In this study, hollow Co9S8 nanotubes were synthesized through a rational morphology design approach. Subsequently, NiSe2 or Co0.85Se was electrodeposited onto the Co9S8 nanotubes, yielding two core-shell heterostructure arrays, namely, NiSe2@Co9S8 and Co0.85Se@Co9S8. By fully leveraging the advantages and synergistic effects of these dual-phase heterostructures, the NiSe2@Co9S8 and Co0.85Se@Co9S8 configurations demonstrated outstanding areal capacitances of 12.54 F cm-2 and 9.61 F cm-2, respectively, at 2 mA cm-2. When integrated with activated carbon in hybrid supercapacitors, the NiSe2@Co9S8//AC and Co0.85Se@Co9S8//AC devices exhibited excellent energy storage performance, with energy densities of 0.959 mW h at 1.681 mW and 0.745 mW h at 1.569 mW, respectively. Additionally, these hybrid supercapacitors demonstrated remarkable cycling stability, with capacitance retention of 87.5% and 89.5% after 5000 cycles for NiSe2@Co9S8//AC and Co0.85Se@Co9S8//AC, respectively. This study provides a novel approach to the synthesis of multiphase core-shell heterostructures based on metal sulfides and selenides, opening new avenues for future research.
RESUMEN
Doping heteroatoms into metal phosphides to modify their electronic structure is an effective method, but the incomplete exposure of active sites is its inherent drawback. In this experiment, both Se doping and P vacancies are simultaneously introduced into CoP-Fe2P (named CoFe-P-Se) to enhance the internal reactivity. Benefiting from the unique hollow porous structure derived from the MOF-on-MOF template, as well as the enhanced intrinsic activity achieved by P defects and Se doping, CoFe-P-Se exhibits a high specific capacitance of 8.41 F cm-2 at a current density of 2 mA cm-2 when used as a supercapacitor electrode. When assembled into a hybrid supercapacitor with activated carbon, the energy density reaches 0.488 mWh cm-2 at a power density of 1.534 mW cm-2, and the capacity retention after 5000 charge-discharge cycles is as high as 90.65%. As an oxygen evolution reaction (OER) electrode, the CoFe-P-Se electrode shows a low overpotential of only 230 mV at a current density of 10 mA cm-2 and 278 mV at 100 mA cm-2. Additionally, it exhibits excellent stability for over 50 h at a current density of 100 mA cm-2. The designed element doping and vacancy engineering in this work will provide an insight for constructing high-performance electrodes.