Optical Science and Photonics in Africa: introduction.

Optical science and photonics are driving the world's advancement of knowledge and economy, encompassing important areas such as green photonics, bio-photonics, agro-photonics, environmental photonics, and so on. These areas are at the heart of the needed development for the African continent. This feature issue will discuss some of the works being conducted in these areas in African photonics research laboratories and will inform researchers in Africa of the current works in optics and photonics taking place.

High electrochemical performance of nickel cobaltite@biomass carbon composite (NiCoO@BC) derived from the bark of for supercapacitor application.

Biomass carbon-based materials are highly promising for supercapacitor (SC) electrodes due to their availability, environment-friendliness, and low cost. Herein, an easy energy-saving hydrothermal process was used to produce NiCoO/NiOOH (NiCoO) composites with biomass carbon (BC) derived from the bark of (AO) at different synthesis time durations (2 h, 4 h, 8 h, 16 h). The structural and morphological properties of the samples were analysed using XRD, Raman spectroscopy, XPS, SEM, TEM and BET, and the results exhibit the presence of carbon inserted into the nickel-cobalt hydroxide matrix.

Enhanced Electrochemical Behavior of Peanut-Shell Activated Carbon/Molybdenum Oxide/Molybdenum Carbide Ternary Composites.

Biomass-waste activated carbon/molybdenum oxide/molybdenum carbide ternary composites are prepared using a facile in-situ pyrolysis process in argon ambient with varying mass ratios of ammonium molybdate tetrahydrate to porous peanut shell activated carbon (PAC). The formation of MoO and MoC nanostructures embedded in the porous carbon framework is confirmed by extensive structural characterization and elemental mapping analysis. The best composite when used as electrodes in a symmetric supercapacitor (PAC/MoO/MoC-1//PAC/MoO/MoC-1) exhibited a good cell capacitance of 115 F g with an associated high specific energy of 51.

Ex-situ nitrogen-doped porous carbons as electrode materials for high performance supercapacitor.

Nitrogen (N) doping of porous carbon materials is an effective strategy for enhancing the electrochemical performance of electrode materials. Herein, we report on ex-situ (post) nitrogen-doped porous carbons prepared using a biomass waste, peanut shell (PS) as a carbon source and melamine as the nitrogen source. The synthesis method involved a two-step mechanism, initial chemical activation of the PS using KOH and post N-doping of the activated carbon.

Nitridation Temperature Effect on Carbon Vanadium Oxynitrides for a Symmetric Supercapacitor.

In this work, porous carbon-vanadium oxynitride (C-VNO) nanostructures were obtained at different nitridation temperature of 700, 800 and 900 °C using a thermal decomposition process. The X-ray diffraction (XRD) pattern of all the nanomaterials showed a C-VNO single-phase cubic structure. The C-VNO obtained at 700 °C had a low surface area (91.

Three dimensional vanadium pentoxide/graphene foam composite as positive electrode for high performance asymmetric electrochemical supercapacitor.

The electrochemical performance of hydrothermal synthesized three dimensional (3D) orthorhombic vanadium pentoxide (VO) nanosheets and vanadium pentoxide/graphene foam (VO/GF) composites at different mass loading of GF were successfully studied. The optimized VO/GF-150 mg composite provided a high specific capacity of 73 mA h g, which was much higher than that the pristine VO (60 mA h g) nanosheets at a specific current of 1 A g. A hybrid capacitor was also fabricated by adopting a carbon-based negative electrode obtained from the pyrolysis of an iron-PANI polymer (C-Fe/PANI) mixture and the 3D VO/GF-150 mg composite as the positive electrode in 6 M KOH electrolyte.