A new approach to synthesize graphene is oxidizing graphite powder with a mixture of H₂SO₄/H₃PO₄ acids and potassium permanganate. Parameters such as reaction time, reaction temperature, and amount of concentration were varied to study the degree of oxidation of graphite to graphene oxide. Currently, an improved method for the preparation of graphene oxide was the most common one. A mixture of H₂SO₄/H₃PO₄ (9 : 1 volume ratio) instead of only H₂SO₄ resulted in increased hydrophilic and oxidized GO without the emission of toxic gas, which differs from the traditional Hummers’ method. The graphene oxide (GO) was converted to reduced graphene oxide (rGO) by chemical reduction using ascorbic acid as the reducing agent. The GO and rGO were characterized by UV-visible spectroscopy, FTIR spectroscopy, and X-ray diffraction patterns. The result showed that treating graphite powder with potassium permanganate (1 : 9) and a mixture of concentrated H₂SO₄/H₃PO₄ acids at 50°C for 12 hours resulted in a better oxidation degree. The designed synthesis strategy could be easily controlled and is an alternative green approach for the production of graphene oxide and reduced graphene oxide.

Dye-sensitized solar cells (DSSCs) are under extensive research works due to their appealing features such as low production costs. The production costs and energy conversion efficiency of DSSCs is strongly influenced by the types of dyes used to harvest photons. Natural dyes extracted from different sources are emerged as a potential candidates to synthetic photosensitizers due to their merit properties including low cost, complete biodegradability, availability and less environmental concern. In order to improve the energy conversion efficiency of natural photosensitizers, blending of different dyes, co-pigmentation of dyes, acidifying of dyes and other approaches have been conducted by researchers, resulting in appreciable performance. This paper reviews the factors affecting the stability of anthocyanin pigments and also the solvents needed for efficient extraction of anthocyanins. Moreover, the potential application of anthocyanin dyes as photosensitizers for DSSC along with the work done over the years is covered.

Nowadays, addressing the drawbacks of liquid electrolyte-based batteries is a hot and challenging issue, which is supposed to be fulfilled through solid electrolyte systems such as polymer electrolytes. Polymer blend electrolytes (PBEs) are widely investigated as viable options to solve the undesired characteristics of their liquid counterparts and also the poor ionic conductivity of homopolymer-based electrolytes. Even though PBEs outperform homopolymer-based electrolytes in terms of performance, the conductivity of pristine PBEs is quite low for practical applications (i.e. below 10^–3 S/cm at room temperature). A very promising approach to solve this limitation is to incorporate additives into the electrolyte systems, to select suitable polymeric materials and to employ the desired synthesizing techniques as the performance of PBEs is strongly dependent on the selection of polymeric materials (i.e. on the inherent properties of polymers), the nature and amount of salts and other additives, and also the techniques employed to synthesize the polymer blend hosts and/or polymer blend electrolytes, determining the functionality, amorphousness, dielectric constant, dimensional stability, and, ultimately, the electrochemical performances of the system. This paper reviews the different factors affecting the miscibility of polymer blends, PBEs synthesizing techniques, the thermal, chemical, mechanical and electrochemical characteristics of PBEs, and also the challenges and opportunities of PBEs. Moreover, the paper presents the current progress of polymer blend electrolytes as well as future prospects for advancing polymer blend electrolytes in the energy storage sectors.

Stable and active electrocatalysts preparation for the oxygen reduction reaction (ORR) is essential for an energy storage and conversion materials (e.g. metal-air batteries). Herein, we prepared a highly-active MnO₂ and Co₃O₄/MnO₂ nanocomposite electrocatalysts using a facial co-precipitation approach. The electrocatalytic activity was examined in alkaline media with LSV and CV. Additionally, the physicochemical characteristics of the MnO₂ and Co₃O₄/MnO₂ composite materials were studied via SEM, XRD, BET, UV-Vis, TGA/DTA, ICP-OES and FTIR. Morphological studies indicated that a pure MnO₂ has a spherical flower-like architecture, whereas Co₃O₄/MnO₂ nanocomposites have an aggregated needle-like structure. Moreover, from the XRD investigation parameters such as the dislocation density, micro-strain, and crystallite size were analyzed. The calculated energy bandgaps for the MnO₂, Co₃O₄/MnO₂-1-5, and Co₃O₄/MnO₂-1-1 nanocomposites were 3.07, 2.6, and 2.3 eV, correspondingly. The FTIR spectroscopy was also employed to study the presence of M-O bonds (M = Mn, Co). The thermal gravimetric investigation showed that the Co₃O₄/MnO₂ nanocomposite materials exhibited improved thermal stability, confirming an enhanced catalytic activity of ORR for MnO₂/Co₃O₄-1-1 composite materials for ORR. These results confirm that the prepared Co₃O₄/MnO₂ composite materials are promising air electrode candidates for the energy storage and conversion technologies.

This review presents the current developments of various electrolyte systems for secondary zinc air batteries (SZABs). The challenges and advancements in aqueous electrolytes (e.g., alkaline, acidic and neutral) and non-aqueous electrolytes (e.g., solid polymer electrolyte, ionic liquids, gel polymer electrolyte, and deep eutectic solvents) development have been reviewed. Moreover, chemical and physical characteristics of electrolytes such as power density, capacity, rate performance, cyclic ability, and safety that play a vital role in recital of the SZABs have been reviewed. Finally, the challenges and limitations that must be investigated and possible future research areas of SZABs electrolytes are discussed.