Suppressing the metal-metal interaction by CoZn0.5V1.5O4 derived from two-dimensional metal-organic frameworks for supercapacitors

Co2VO4 with Co tetrahedrons and octahedrons of transition metal oxides has achieved progress in electrocatalysts and batteries. However, high metal-metal interactions make it challenging to maintain high reactivity as well as increase the conductivity and stability of supercapacitors. In this work, spinel-structured CoZn0.5V1.5O4 with a high specific surface area was synthesized through an ion-exchange process from the metal-organic frameworks of zinc-cobalt. Density functional theory calculations indicate that the replacement of transition metal by Zn can decrease the interaction between the transition metals, leading to a downshift in the π*-orbitals (V-O) and half-filled a1g orbitals near the Fermi level, thus increasing the conductivity and stability of CoZn0.5V1.5O4. As a supercapacitor electrode, CoZn0.5V1.5O4 exhibits high cycling durability (99.4% capacitance retention after 18,000 cycles) and specific capacitance (1100 mF cm−2 at 1 mA cm−2). This work provides the possibility of designing octahedral and tetrahedral sites in transition metal oxides to improve their electrochemical performance.