Supercapacitors are increasingly used for energy conversion and storage systems in sustainable nanotechnologies. Graphite is a conventional electrode utilized in Li-ion-based batteries, yet its specific capacitance of 372 mA h g −1 is not adequate for supercapacitor applications. Interest in supercapacitors is due to their high-energy capacity, storage for a shorter period and longer lifetime. This review compares the following materials used to fabricate supercapacitors: spinel ferrites, e.g., MFe 2 O 4 , MMoO 4 and MCo 2 O 4 where M denotes a transition metal ion; perovskite oxides; transition metals sulfides; carbon materials; and conducting polymers. The application window of perovskite can be controlled by cations in sublattice sites. Cations increase the specific capacitance because cations possess large orbital valence electrons which grow the oxygen vacancies. Electrodes made of transition metal sulfides, e.g., ZnCo 2 S 4 , display a high specific capacitance of 1269 F g −1 , which is four times higher than those of transition metals oxides, e.g., Zn-Co ferrite, of 296 F g −1. This is explained by the low charge-transfer resistance and the high ion diffusion rate of transition metals sulfides. Composites made of magnetic oxides or transition metal sulfides with conducting polymers or carbon materials have the highest capacitance activity and cyclic stability. This is attributed to oxygen and sulfur active sites which foster electrolyte penetration during cycling, and, in turn, create new active sites.

In the context of climate change and the circular economy, biochar has recently found many applications in various sectors as a versatile and recycled material. Here, we review application of biochar-based for carbon sink, covering agronomy, animal farming, anaerobic digestion, composting, environmental remediation, construction, and energy storage. The ultimate storage reservoirs for biochar are soils, civil infrastructure, and landfills. Biochar-based fertilisers, which combine traditional fertilisers with biochar as a nutrient carrier, are promising in agronomy. The use of biochar as a feed additive for animals shows benefits in terms of animal growth, gut microbiota, reduced enteric methane production, egg yield, and endo-toxicant mitigation. Biochar enhances anaerobic digestion operations, primarily for biogas generation and upgrading, performance and sustainability, and the mitigation of inhibitory impurities. In composts, biochar controls the release of greenhouse gases and enhances microbial activity. Co-composted biochar improves soil properties and enhances crop productivity. Pristine and engineered biochar can also be employed for water and soil remediation to remove pollutants. In construction, biochar can be added to cement or asphalt, thus conferring structural and functional advantages. Incorporating biochar in biocomposites improves insulation, electromagnetic radiation protection and moisture control. Finally, synthesising biochar-based materials for energy storage applications requires additional functionalisation.

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The world is currently facing critical water and energy issues due to the growing population and industrialization, calling for methods to obtain potable water, e.g., by photocatalysis, and to convert solar energy into fuels such as chemical or electrical energy, then storing this energy. Energy storage has been recently improved by using electrochemical capacitors and ion batteries. Research is actually focusing on the synthesis of materials and hybrids displaying improved electronic, physiochemical, electrical, and optical properties. Here, we review molybdenum disulfide (MoS2) materials and hybrids with focus on synthesis, electronic structure and properties, calculations of state, bandgap and charge density profiles, and applications in energy storage and water remediation.

Magnetic spinel ferrite nanoparticles (SFNPs) attract high scientific attention from researchers due to their broad area for biomedicine applications, comprising cancer magnetic hyperthermia and targeted drug delivery. Uniquely, its excellent performance, namely, tuning size and surface morphology, excellent magnetism, extraordinary magnetically heat induction, promising biocompatibility, and specific targeting capacity, is essential for their effective utilization in clinical diagnosis and therapeutics of diseases. This review emphasizes the anticancer properties of nanoparticles of spinel ferrites with extra focus on the most recent literature. A critical review is provided on the latest applications of SFNPs in cancer therapy. Based on the results obtained from this review, SFNPs have the indefinite ability in cancer therapy through two mechanisms: (1) hyperthermia, where SFNPs, used as a hyperthermia mediator, elevated the tumor cells heat post-exposure to an external magnetic field and radiosensitizer during cancer radiotherapy; and (2) targeted drug delivery of cytotoxic drugs in tumor treatment. SFNPs induced apoptosis and cell death of cancer cells and prevented cancer cell proliferation.