The advanced electrochemical properties, such as high energy density, fast charge–discharge rates, excellent cyclic stability, and specific capacitance, make supercapacitor a fascinating electronic device. During recent decades, a significant amount of research has been dedicated to enhancing the electrochemical performance of the supercapacitors through the development of novel electrode materials. In addition to highlighting the charge storage mechanism of the three main categories of supercapacitors, including the electric double-layer capacitors (EDLCs), pseudocapacitors, and the hybrid supercapacitors, this review describes the insights of the recent electrode materials (including, carbon-based materials, metal oxide/hydroxide-based materials, and conducting polymer-based materials, 2D materials). The nanocomposites offer larger SSA, shorter ion/electron diffusion paths, thus improving the specific capacitance of supercapacitors (SCs). Besides, the incorporation of the redox-active small molecules and bio-derived functional groups displayed a significant effect on the electrochemical properties of electrode materials. These advanced properties provide a vast range of potential for the electrode materials to be utilized in different applications such as in wearable/portable/electronic devices such as all-solid-state supercapacitors, transparent/flexible supercapacitors, and asymmetric hybrid supercapacitors.

The conversion of carbon dioxide (CO2) into fuels and value-added products is one of the most significant inventions to address the global warming and energy needs. Photoelectrochemical (PEC) CO2 conversion can be considered as artificial photosynthesis technique which produces formate, formaldehyde, formic acid, methane, methanol, ethanol, etc. Recent advances in electrode materials, mechanisms, kinetics, thermodynamics, and reactor designs of PEC CO2 conversion have been comprehensively reviewed in this article. The adsorption and activation of CO2/intermediates at the electrode surface are the key steps for improving the kinetics of CO2 conversion. PEC efficiency could be upgraded through the utilization of 2D/3D materials, plasmonic metals, carbon-based catalysts, porous nanostructures, metal organic frameworks, molecular catalysts, and biological molecules. The defect engineered (by cation/anion vacancy, crystal distortion, pits, and creation of oxygen vacancies) 2D/3D materials, Z-scheme heterojunctions, bio-electrodes, and tandem photovoltaic-PEC reactors are the suitable options to enhance the efficiency at low external bias.

Photocatalytic water splitting is a sustainable technology for the production of clean fuel in terms of hydrogen (H₂). In the present study, hydrogen (H₂) production efficiency of three promising photocatalysts (titania (TiO₂-P25), graphitic carbon nitride (g-C₃N₄), and cadmium sulfide (CdS)) was evaluated in detail using various sacrificial agents. The effect of most commonly used sacrificial agents in the recent years, such as methanol, ethanol, isopropanol, ethylene glycol, glycerol, lactic acid, glucose, sodium sulfide, sodium sulfite, sodium sulfide/sodium sulfite mixture, and triethanolamine, were evaluated on TiO₂-P25, g-C₃N₄, and CdS. H₂ production experiments were carried out under simulated solar light irradiation in an immersion type photo-reactor. All the experiments were performed without any noble metal co-catalyst. Moreover, photolysis experiments were executed to study the H₂ generation in the absence of a catalyst. The results were discussed specifically in terms of chemical reactions, pH of the reaction medium, hydroxyl groups, alpha hydrogen, and carbon chain length of sacrificial agents. The results revealed that glucose and glycerol are the most suitable sacrificial agents for an oxide photocatalyst. Triethanolamine is the ideal sacrificial agent for carbon and sulfide photocatalyst. A remarkable amount of H₂ was produced from the photolysis of sodium sulfide and sodium sulfide/sodium sulfite mixture without any photocatalyst. The findings of this study would be highly beneficial for the selection of sacrificial agents for a particular photocatalyst.

Surface contamination by microbes is a major public health concern. A damp environment is one of potential sources for microbe proliferation. Smart photocatalytic coatings on building surfaces using semiconductors like titania (TiO₂) can effectively curb this growing threat. Metal-doped titania in anatase phase has been proven as a promising candidate for energy and environmental applications. In this present work, the antimicrobial efficacy of copper (Cu)-doped TiO₂ (Cu-TiO₂) was evaluated against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) under visible light irradiation. Doping of a minute fraction of Cu (0.5 mol %) in TiO₂ was carried out via sol-gel technique. Cu-TiO₂ further calcined at various temperatures (in the range of 500–700 °C) to evaluate the thermal stability of TiO₂ anatase phase. The physico-chemical properties of the samples were characterized through X-ray diffraction (XRD), Raman spectroscopy, X-ray photo-electron spectroscopy (XPS) and UV–visible spectroscopy techniques. XRD results revealed that the anatase phase of TiO₂ was maintained well, up to 650 °C, by the Cu dopant. UV–vis results suggested that the visible light absorption property of Cu-TiO₂ was enhanced and the band gap is reduced to 2.8 eV. Density functional theory (DFT) studies emphasize the introduction of Cu⁺ and Cu²⁺ ions by replacing Ti⁴⁺ ions in the TiO₂ lattice, creating oxygen vacancies. These further promoted the photocatalytic efficiency. A significantly high bacterial inactivation (99.9999%) was attained in 30 min of visible light irradiation by Cu-TiO₂.

Reports of recent fire accidents in the electronics and electric vehicles (EVs) industries show that thermal runaway (TR) reactions are a key consideration for the industry. Utilization of solid electrolytes (SEs) could be an important solution in to the TR issues connected to exothermic electrochemical reactions. Data on the thermal stability of modern SEs, ionic transport mechanisms, kinetics, thermal models, recent advances, challenges, and future prospects are presented in this review. Ceramic polymer nanocomposites are the most appropriate SEs for high‐temperature stable batteries (in the range of 80–200 °C). Hydrogels and ionogels can be employed as stable, flexible, and mechanically durable SEs for antifreeze (up to –50 °C) and high‐temperature (up to 200 °C) applications in supercapacitors. Besides the thermal safety features, SEs can also prolong the lifecycle of energy storage devices in next‐generation EVs, space devices, aviation gadgets, defense tools, and mobile electronics.