Rayavarapu Prasada Rao

Biomass resources are often disposed of inefficiently and it causes environmental degradation. These wastes can be turned into bio‐products using effective conversion techniques. The synthesis of high‐value bio‐products from biomass adheres to the principles of a sustainable circular economy in a variety of industries, including agriculture. Recently, fluorescent carbon dots (C‐dots) derived from biowastes have emerged as a breakthrough in the field, showcasing outstanding fluorescence properties and biocompatibility. The C‐dots exhibit unique quantum confinement properties due to their small size, contributing to their exceptional fluorescence. The significance of their fluorescent properties lies in their versatile applications, particularly in bio‐imaging and energy devices. Their rapid and straight‐forward production using green/chemical precursors has further accelerated their adoption in diverse applications. The use of green precursors for C‐dot not only addresses the biomass disposal issue through a scientific approach, but also establishes a path for a circular economy. This approach not only minimizes biowaste, which also harnesses the potential of fluorescent C‐dots to contribute to sustainable practices in agriculture. This review explores recent developments and challenges in synthesizing high‐quality C‐dots from agro‐residues, shedding light on their crucial role in advancing technologies for a cleaner and more sustainable future.

Solid‐state battery research has gained significant attention due to their inherent safety and high energy density. Silicon anodes have been promoted for their advantageous characteristics, including high volumetric capacity, low lithiation potential, high theoretical and specific gravimetric capacity, and the absence of lethal dendritic growth. Addressing concerns such as low conductivity, pulverization, fracture, dense solid electrolyte interface layer, and low coulombic efficiency has substantially improved the use of silicon electrodes in solid‐state batteries. Researchers have explored carbon additions, solid electrolyte suitability for Si anodes, pressure optimization, and particle size effects (nano/micro) to enhance energy density. Recent studies have investigated the conductivity mechanism, stack pressure, and anode‐solid electrolyte compatibility to improve energy density. Micro‐ and nano‐sized silicon have attracted attention in carbon‐based composites due to their exceptional conductivity, uniform distribution, efficient electron migration, and diffusion channels. The development of solid‐state batteries with high energy density, safety, and extended lifespan has been a major focus. This review sheds light on significant insights and strategic approaches for researchers working on solid‐state silicon‐based systems to overcome existing challenges.

Lithium-air batteries exhibits high practical energy densities ranging from 1000 to 4000 Wh Kg⁻¹, rendering them appealing for applications in portable electronic devices and electric vehicles. Nevertheless, they grapple with challenges like low charge–discharge efficiency, limited stability over multiple cycles, and electrode degradation stemming from undesirable side reactions, thus impeding their commercial market. In this study, ϵ-MnO₂ petal-like nanostructures were synthesized on Ni foam via simple, microwave-assisted synthesis approach. The resulting ϵ-MnO₂/Ni electrode demonstrated storage capacities (1982 mAh g⁻¹ discharge capacity at 200 mA g⁻¹) alongside enhanced cyclability and stability over 100 cycles, independent of discharge depth. This electrochemical performance can be attributed to its 3D morphology, oxygen defects, and the absence of side reactions from carbon-based additives. Overall, ϵ-MnO₂/Ni electrode catalysts hold potential for realizing cost-effective Li-O₂ based energy storage technologies.

Electronic devices commonly use rechargeable Li-ion batteries due to their potency, manufacturing effectiveness, and affordability. Electrospinning technology offers nanofibers with improved mechanical strength, quick ion transport, and ease of production, which makes it an attractive alternative to traditional methods. This review covers recent morphology-varied nanofibers and examines emerging nanofiber manufacturing methods and materials for battery tech advancement. The electrospinning technique can be used to generate nanofibers for battery separators, the electrodes with the advent of flame-resistant core-shell nanofibers. This review also identifies potential applications for recycled waste and biomass materials to increase the sustainability of the electrospinning process. Overall, this review provides insights into current developments in electrospinning for batteries and highlights the commercialization potential of the field.

With growing environmental and ecological concerns, innovative energy storage systems are urgently required to develop smart grids and electric vehicles (EVs). Since their invention in the 1970s, rechargeable lithium-ion batteries (LIBs) have risen as a revolutionary innovation due to their superior benefits of high operating potential and energy density. Similarly, fuel cells, especially Proton Exchange Membrane Fuel Cells (PEMFC) and Solid-Oxide Fuel Cells (SOFC), have been developed as an energy storage system for EVs due to their compactness and high-temperature stability, respectively. Various attempts have been made to explore novel materials to enhance existing energy storage technologies. Materials design and development are significantly based on trial-and-error techniques and require substantial human effort and time. Additionally, researchers work on individual materials for specific applications. As a viewpoint, we present the available sustainable routes for electrochemical energy storage, highlighting the use of (i) green materials and processes, (ii) renewables, (iii) the circular economy approach, (iv) regulatory policies, and (v) the data driven approach to find the best materials from several databases with minimal human involvement and time. Finally, we provide an example of a high throughput and machine learning assisted approach for optimizing the properties of several sustainable carbon materials and applying them to energy storage devices. This study can prompt researchers to think, advance, and develop opportunities for future sustainable materials selection, optimization, and application in various electrochemical energy devices utilizing ML.

Low CO ₂ emitting energy extraction techniques and their application in healthcare, textile and smart wearables.

Layered sodium iron phosphate phase [Na₃Fe₃(PO₄)₄] was synthesized by solution combustion synthesis method, marking the first attempt of solvothermal synthesis of this phase. Its crystal structure was verified by synchrotron and neutron powder diffraction. Rietveld analyses proved the phase purity and formation of monoclinic framework with C2/c symmetry. It undergoes an antiferromagnetic ordering ∼27 K. This combustion prepared nanoscale Na₃Fe₃(PO₄)₄ compound was found to be electrochemically active with a stepwise voltage profile involving an Fe³⁺/Fe²⁺ redox activity centred at 2.43 V vs. Na/Na⁺. Despite various cathode optimization, only 1.8 Na⁺ per formula unit could be reversibly inserted into the Na₃Fe₃(PO₄)₄ framework leading to capacity close to 50 mAh g⁻¹. This limited electrochemical activity can be rooted to (i) relatively large diffusion barrier (ca. 0.28 eV) as per Bond valence site energy (BVSE) calculations and (ii) possible structural instability during (de)sodiation reaction.

Fast-ion conducting Na₁₁Sn₂PS₁₂prepared by ball-milling allowed us to realize the first all-solid-state Na–Se battery, which can reach 500 charge–discharge cycles at room temperature.