Efficient photoelectrochemical water oxidation and electrochemical supercapacitor performance.

What is it about?

ZnAl2O4 hexagonal microstructure (ZAO) was prepared using the co-precipitation assisted hydrothermal technique. The prepared ZAO exhibits a hexagon morphology. Optical properties study reveals the reduction of bandgap (3.05 eV) thank bulk ZAO materials. The photoelectrochemical (PEC) performance was significantly improved in the presence of light illumination and provides the photocurrent density of 1.32 mA/cm2 under the light-on conditions of linear sweep voltammetry (LSV) measurement. The ZAO materials provide very good photostability over the long period of time. A detailed analysis of the electrochemical supercapacitor performance of ZAO electrode materials was analyzed through cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS) studies. The ZAO electrode material shows the specific capacity of 255.4 mAh g−1 at the current density of 1A g−1. The ZAO electrode shows rate capability of ～67 % with cycle stability of 70 % at current density of 6 A g−1 over 500 cycles. The columbic efficiency of the electrode was found to be 98 % after 500 GCD cycles. According to the existing literature, this is the first report on ZAO's performance in supercapacitor applications and opens up new avenues for the exploration of other materials in ZAO - based materials for energy storage.

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Why is it important?

Huge amount of energy is required for the survival of industries in all sectors of the world and for the continued development of civilization. Innovative and uncomplicated new energy storage systems are important to replace fossil fuels in the future [1], [2]. Solar energy is a pure, abundant and environmentally friendly energy source. It is used in the photoelectrochemical process to convert solar energy into chemical energy. The principle behind this process is that the photoinduced electron-hole pairs are separated and begin the process of oxidation and reduction to produce hydrogen and oxygen [3]. Metal oxides have been extensively tested for PEC performance and proven to be one of the best class materials for further research. Further, supercapacitors are electronic devices that store and transfer energy over time, which play a major role in future transport systems [4], [5]. Increasing power demands can be met by using supercapacitors in combination with lithium-ion batteries. Spinel semiconductors are comprised of a group of metal oxides having a chemical complex AB2O4, where A and B are di and trivalent cations, respectively [6].

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