Spinel ZnCo2O4 nanosheets as carbon and binder free electrode material for energy storage and electroreduction of H2O2

Abstract

We present simple surfactant free hydrothermal method followed by calcination process to in situ fabricate ZnCo2O4 material on Ni foam with two distinctly different morphologies. The interconnected nanosheets (ZnCo2O4-H) and bundle-like nanosheets (ZnCo2O4-U) morphologies of ZnCo2O4 material are seeded on Ni foam using hexamethylenetetramine and urea as precipitating agents. These nanosheets on Ni foams consist of large number of mesopores with BET surface areas varying between 88 and 112 m2 g−1. The Ni foams seeded with ZnCo2O4 nanosheets are directly used as electrodes to evaluate their charge storage performance and electrocatalytic activity for hydrogen peroxide reduction in alkaline medium. The interconnected nanosheets exhibit high specific capacitance value of 1102 F g−1 compared to 653 F g−1 of bundle-like nanosheets at a current density of 1 A g−1. The bundle-like nanosheets of zinc cobalt oxide material shows excellent rate capability with 77% capacitance retention at 16 A g−1. Interestingly both showed excellent capacitance retention over 5000 galvanostatic charge-discharge cycles at very high current densities. Furthermore, both the materials are very effective for hydrogen peroxide reduction. In the presence of 0.5 M H2O2 the cathodic current increased by about 100 times for interconnected nanosheets electrode and 30 times for bundle-like nanosheets electrode compared to H2O2 free alkaline solutions. These results consistently show strong correlation between the morphology related properties and electrochemical activity of oxide materials.