Heteroleptic Ruthenium(II) Complexes with 2,2'-Bipyridines Having Carbonitriles as Anchoring Groups for ZnO Surfaces: Syntheses, Physicochemical Properties, and Applications in Organic Solar Cells

Synthesis of New Ruthenium Complexes and Their Exploratory Study as Polymer Hybrid Composites in Organic Electronics

Polymeric hybrid films, for their application in organic electronics, were produced from new ruthenium indanones in poly(methyl methacrylate) (PMMA) by the drop-casting procedure. Initially, the synthesis and structural characterization of the ruthenium complexes were performed, and subsequently, their properties as a potential semiconductor material were explored. Hence hybrid films in ruthenium complexes were deposited using PMMA as a polymeric matrix. The hybrid films were characterized by infrared spectrophotometry and atomic force microscopy. The obtained results confirmed that the presence of the ruthenium complexes enhanced the mechanical properties in addition to increasing the transmittance, favoring the determination of their optical parameters. Both hybrid films exhibited a maximum stress around 10.5 MPa and a Knoop hardness between 2.1 and 18.4. Regarding the optical parameters, the maximum transparency was obtained at wavelengths greater than 590 nm, the optical band gap was in the range of 1.73-2.24 eV, while the Tauc band gap was in the range of 1.68-2.17 eV, and the Urbach energy was between 0.29 and 0.50 eV. Consequently, the above comments are indicative of an adequate semiconductor behavior; hence, the target polymeric hybrid films must be welcomed as convenient candidates as active layers or transparent electrodes in organic electronics.

Recent Progress in High-voltage Aqueous Zinc-based Hybrid Redox Flow Batteries

The energy density of redox flow batteries (RFBs) is generally affected by the standard electrode potential and the solubility of the redox active species. These crucial factors are closely related to the solvent in which the active materials are dissolved. Aqueous RFBs have been widely studied due to their excellent reaction kinetics and high solubility of the redox couple in aqueous media. However, the low voltage of conventional aqueous RFBs has hindered them from being candidates for practical applications. Recently, high-voltage aqueous RFBs are implemented based on the low negative potential of the Zn/[Zn(OH)₄ ]^2- reaction in an alkaline solution. Here, we review recent progress in the design of high energy density RFBs in both aqueous and non-aqueous electrolytes, notably focusing on the Zn/MnO₂ hybrid RFBs in detail. Furthermore, strategies for inhibiting zinc dendritic growth and stabilizing manganese redox couple in the RFBs system are discussed.

Boosting Electrolytic MnO2-Zn Batteries by a Bromine Mediator

An aqueous electrolytic MnO₂-Zn battery with eye-catching Mn²⁺/MnO₂ cathode chemistry has been attracting immense interest for next-generation energy storage devices due to its irreplaceable advantages. However, the limited MnO₂ conductivity restricts its long service life at high areal capacities. Here, we report a high-performance electrolytic MnO₂-Zn battery via a bromine redox mediator, to enhance its electrochemical performance. The MnO₂/Br₂-Zn battery displays a high discharge voltage of 1.98 V with a capacity of ∼5.8 mAh cm^-2. It also shows an excellent rate performance of 20 C with a long-term stability of over 600 cycles. Furthermore, the scaled-up MnO₂/Br₂-Zn battery with a capacity of ∼950 mAh exhibits a stable 100 cycles with a practical cell energy density of ∼32.4 Wh kg^-1 and an attractively low energy cost of below 15 US$ kWh^-1. The design approach can be generalized to other electrodes and battery systems, thus opening up new possibilities for large-scale energy storage.