Recent advances in engineered metal oxide nanostructures for supercapacitor applications: experimental and theoretical aspects

Supercapacitors are widely accepted as one of the energy storage devices in the realm of sustainable and renewable energy storage. Supercapacitors have emerged as a good alternative to traditional capacitors and fuel cells due to their higher energy density and power density compared to batteries and fuel cells. However, supercapacitors have some drawbacks such as low energy density and poor cycle life compared to batteries. To overcome these issues, researchers are paying much attention to the fabrication of metal oxide nanostructures and their modification by different approaches such as doping, introducing oxygen vacancies, and hybridization with nanomaterials of carbon allotropes for enhanced electrochemical properties. In this review article, we have presented the above-mentioned topics with the aid of recently reported works. Moreover, we have provided theoretical insights from density functional theory for the electrochemical behavior of the electrode materials from the published works. This review concisely presents the advancement in the supercapacitor energy storage field and the different approaches involved in the fabrication of supercapacitor electrode materials, which will be very handy to the researchers working in the field of energy storage. Further, the challenges and future perspectives of this exciting research field are discussed in detail.