Green supercapacitors: review and perspectives on sustainable template-free synthesis of metal and metal oxide nanoparticles

Abstract

Researchers are committed to thoroughly investigating the sustainable production of supercapacitor electrode materials with enhanced properties. Supercapacitors are promising energy storage devices due to their high power density, stability, rapid energy storage, and fast delivery, but most materials employed for the fabrication of electrodes are toxic and not environmentally friendly. Thus, to overcome this issue, there has been considerable interest in green, eco-friendly, biocompatible, and biodegradable materials for use in various energy devices. Modified electrode materials are created through phytosynthesis, which have been proven to act as excellent reducing agents and improved catalysts, while maintaining a desirable shape and size, making them ideal for use as noble supercapacitor electrode materials. To fully realize the capabilities of using plant extracts to assemble nano-energy materials in different dimensions, it is important to have a thorough comprehension of the structure and properties of natural components and micro/nanostructures. This review provides an outline of the latest advancements in the design and construction of free-standing supercapacitor electrodes using plant-based materials. Initially, we emphasize the importance of green synthesis and phytosynthesis characteristics, including the factors affecting them and their plausible mechanisms. Further, we outline phytosynthesized nanomaterials and composites for supercapacitor applications with basic technology. We aim to systematically discuss the potential impact of greener methods using various plant-based synthesized metal nanoparticles (such as Ti, V, Cr, Mn, Ni, Fe, Co, Zn, Cu, Ni, W, Au, and Pt) for supercapacitor application and their conceivable mechanism. We conclude with a summary of the challenges for the future development of sustainable supercapacitor electrode materials.