Insight into photoelectrocatalytic mechanisms of bifunctional cobaltite hollow-nanofibers towards oxygen evolution and oxygen reduction reactions for high-energy zinc-air batteries

Photo-Assisted Metal-Air Batteries: Recent Progress, Challenges and Opportunities

To meet the need of high energy density, long durability, safe and cost-efficient energy conversion and storage devices, metal-air batteries like Li-O₂ and Zn-O₂ batteries have received enormous attention and were subject to exciting development in the past decade. Photo-assisted strategies that enable the effective combination of photo/electric energy conversion/storage render a new dimension for the conventional metal-air batteries techniques with mere electric energy utilization. Therefore, tremendous research is ongoing in search of more efficient and durable devices with photo-assisted strategies. This review provides an overview of photo-assisted Li-O₂ batteries, Zn-O₂ batteries, and batteries with various metal/air components. The working mechanism, the basic device architecture and practical performances of various photo-assisted systems are summarized and discussed. Furthermore, certain technical challenges and future opportunities for the photo-assisted metal air batteries are emphasized and discussed in the hope of stimulating further research.

Nanoparticles of Mixed-Valence Oxides MnXCO3-XO4 (0 ≤ X ≤ 1) Obtained with Agar-Agar from Red Algae (Rhodophyta) for Oxygen Evolution Reaction

The development of efficient electrocatalysts for the oxygen evolution reaction (OER) is of paramount importance in sustainable water-splitting technology for hydrogen production. In this context, this work reports mixed-valence oxide samples of the Mn_XCo_3-XO₄ type (0 ≤ X ≤ 1) synthesized for the first time by the proteic sol-gel method using Agar-Agar as a polymerizing agent. The powders were calcined at 1173 K, characterized by FESEM, XRD, RAMAN, UV-Vis, FT-IR, VSM, and XPS analyses, and were investigated as electrocatalysts for the oxygen evolution reaction (OER). Through XRD analysis, it was observed that the pure cubic phase was obtained for all samples. The presence of Co³⁺, Co²⁺, Mn²⁺, Mn³⁺, and Mn⁴⁺ was confirmed by X-ray spectroscopy (XPS). Regarding the magnetic measurements, a paramagnetic behavior at 300 K was observed for all samples. As far as OER is concerned, it was investigated in an alkaline medium, where the best overpotential of 299 mV vs. RHE was observed for the sample (MnCo₂O₄), which is a lower value than those of noble metal electrocatalysts in the literature, together with a Tafel slope of 52 mV dec^-1, and excellent electrochemical stability for 15 h. Therefore, the green synthesis method presented in this work showed great potential for obtaining electrocatalysts used in the oxygen evolution reaction for water splitting.

Modification of glassy carbon electrode with manganese cobalt oxide-cubic like structures incorporated graphitic carbon nitride sheets for the voltammetric determination of 2,4,6 -trichlorophenol

Novel cube-like transition metal oxide embedded on graphitic carbon nitride (MCO@GCN) formed a hybrid composite via hydrothermal assisted sonochemical synthesis. The synthesized composite was examined with various physical characterizations such as morphological SEM, EDX, XRD, and FT-IR spectroscopy. The electrocatalytic activity of MCO@GCN composite was further investigated when used  to modify a glassy carbon electrode (GCE). The electrochemical sensor was investigated using modified MCO@GCN/GCE towards environmental pollutant 2,4,6-trichlorophenol (2,4,6-TCP) detection with at a potential of (+ 0.654 V vs Ag/AgCl) in pH-7. The structural features have favored a high charge transfer ratio with excellent conductivity which showed a low detection limit (LOD) of 0.0068 μM and sensitivity of 23.57 μA·μM^-1·cm^-2 comprising a wide linear working range of 0.01-1720 μM by using differential pulse voltammetry. Besides, the MCO@GCN/GCE displayed excellent selectivity , repeatability, reproducibility, storage, and operational stability. Notably, the proposed MCO@GCN/GCE was validated with different environmental samples (tap, river, and industrial water) with RSD 0.62-2.86% and 96.51-99.66% (n = 3) recovery.