α-MnO2 composite with gold nanoparticles on carbon cloth modified with MOFs-derived porous carbon for flexible and activity-enhanced sodium-ion supercapacitors

Improving the catalytic activity of electrodes in a limited space is crucial to energy storage devices such as supercapacitors. Herein, the surface activity of the flexible electrode (Au-MnO2/CPCN@CC) is enhanced by combining gold particles (AuNPs) modified alpha-MnO2 with conductive porous carbon nanoflakes (CPCN) derived from the metal-organic framework (MOF) on carbon cloth (CC). The Au-MnO2/CPCN@CC electrode exhibits a higher specific capacity of 503.7 F/g at 0.125 mA/cm2 and retains 87.68% capacity after 10,000 cycles in 1 M Na2SO4, while the structure without AuNPs achieves 242.6 F/g and 61.07% capacity retention after 10,000 cycles. The high stability of Au-MnO2/CPCN@CC stems from the good pseudocapacitance ratio of 83.80% at 1 mV/s compared to 78.43% of MnO2/CPCN@CC and 40.88% of Au/CPCN@CC. The supercapacitor assembled with Au-MnO2/CPCN@CC as the positive electrode and activated carbon (AC) as the negative electrode in 1 M NaPF6 shows an excellent power density of 79.96 W/kg at 71.48 Wh/kg as well as 81.93% capacitance retention after 10,000 cycles. Density-functional theory (DFT) calculations of Au-MnO2/CPCN composite reveal a sodium ion adsorption energy of 3.744 eV and a large DOS near Fermi level. Hence, Au nanoparticles (AuNPs) and MOFsderived CPCN lead to enhanced surface electron transport of MnO2 and ultimately superior performance.

Automated summary

In this study, the surface activity of the electrode is enhanced by combining gold particles and MOF-derived CPCN with α-MnO2. The Au-MnO2/CPCN@CC electrode exhibits higher specific capacity and better cycling stability in 1 M Na2SO4. The use of Au nanoparticles and CPCN improves the surface electron transport of MnO2, resulting in superior performance.