Application of green-synthesized cadmium oxide nanofibers and cadmium oxide/graphene nanosheet nanocomposites as alternative and efficient photocatalysts for methylene blue removal from aqueous matrix.

For the first time, cadmium oxide (CdO) nanofibers (NFs) and graphene nanosheet (GNS)-doped CdO nanocomposites (NCs) have been synthesized by a simple green route using green tea (Camellia sinensis) extract, for subsequent application as photocatalysts for methylene blue (MB) removal from an aqueous matrix. In addition, the materials were tested as working electrodes for supercapacitors. The prepared samples were analyzed by FESEM, UV-Vis spectroscopy, FTIR, and X-ray diffraction (XRD). FESEM revealed that the obtained NPs and NCs show fiber-shaped nanostructure. FTIR confirmed the presence of biomolecules on CdO and carbon compounds on CdO/GNS, while XRD exhibited the cubic crystalline structure of obtained NPs and NCs. The Rietveld refinement using XRD data was performed to ascertain the crystallographic characteristics of the produced samples and look into lattice imperfections. UV-Vis spectroscopy evaluated the optical bandgap energies of CdO and CdO/GNS NCs. The CdO/GNS NCs demonstrated a fast cleavage of the dye molecule under UV irradiation, resulting in 97% removal in 120 min. In addition, CdO/GNS NCs showed remarkable chemical stability as an electrode material, with a high specific capacitance of 231 F g-1 at a scan rate of 25 mV s-1. These observed NCs characteristics are higher when compared to pristine CdO NPs. Finally, we found that the investigated NCs showed enhanced multifunctional properties, such as photocatalytic and supercapacitor characteristics, which can be useful in practical applications.

Remarkable photocatalytic performances towards pollutant degradation under sunlight and enhanced electrochemical properties of TiO2/polymer nanohybrids.

In this work, TiO2-based nanocomposites containing polyaniline (PANI), poly(1-naphthylamine) (PNA), and polyindole (PIN) were synthesized by effective and simple routes and posteriorly employed as photocatalysts and supercapacitors. Characterization techniques such as XRD, FTIR, FESEM, UV, and PL were employed to investigate the structural, morphological, and optical properties of materials. XRD analysis confirmed the successful formation of TiO2 and TiO2/polymer nanocomposites. PANI, PNA, and PIN polymers were well distributed on the surface of TiO2 nanoparticles and were investigated/explored from the FESEM analysis. The visible light absorption and the recombination rate of photogenerated charge carriers were confirmed by the UV-Vis and PL analysis. The photocatalytic properties of the nanocomposites were investigated towards malachite green (MG) dye degradation under sunlight. The dye degradation efficiency followed the order TiO2/PNA > TiO2/PANI > TiO2 > TiO2/PIN. The higher efficiency of TiO2/PNA can be associated with its smaller bandgap energy compared to the other materials. Electrochemical properties of materials were also examined by cyclic voltammetry and galvanostatic charge-discharge measurements using a three-electrode experiment setup in an aqueous electrolyte. TiO2/PNA nanocomposite showed higher supercapacitor behavior compared to the other materials due to higher electrical conductivity of PNA and redox potential of TiO2 (pseudocapacitance).

Poly(1-Napthylamine) Nanoparticles as Potential Scaffold for Supercapacitor and Photocatalytic Applications.

Herein, we explore the supercapacitor and photocatalytic applications of poly(1-naphthylamine) (PNA) nanoparticles. The PNA nanoparticles were synthesized by using polymerization of 1-naphthylamine and characterized with several techniques in order to understand the morphological, structural, optical and compositional properties. The structural and morphological properties confirmed the formation of crystalline nanoparticles of PNA. The Fourier-transform infrared (FTIR) spectrum revealed the successful polymerization of 1-naphthylamine monomer to PNA. The absorption peaks that appeared at 236 and 309 nm in the UV−Vis spectrum for PNA nanoparticles represented the π−π* transition. The supercapacitor properties of the prepared PNA nanoparticles were evaluated with cyclic voltammetry (CV) and galvanostatic charge−discharge (GCD) methods at different scan rates and current densities, respectively. The effective series resistance was calculated using electrochemical impedance spectroscopy (EIS), resulting in a minimum resistance value of 1.5 Ω. The highest specific capacitance value of PNA was found to be 255 Fg−1. This electrode also exhibited excellent stability with >93% capacitance retention for 1000 cycles, as measured at 1A g−1. Further, the prepared PNA nanoparticles were used as an effective photocatalyst for the photocatalytic degradation of methylene blue (MB) dye, which exhibited ~61% degradation under UV light irradiation. The observed results revealed that PNA nanoparticles are not only a potential electrode material for supercapacitor applications but also an efficient photocatalyst for the photocatalytic degradation of hazardous and toxic organic dyes.

Remarkable sunlight-driven photocatalytic performance of Ag-doped ZnO nanoparticles prepared by green synthesis for degradation of emerging pollutants in water.

In this work, Ag-doped ZnO nanoparticles (NPs) were synthesized by a simple green method using a toxic agent-free route for photocatalytic purposes, toward methylene blue (MB) removal in water under sunlight irradiation. The effects of operating parameters, such as catalyst dosage, dye concentration, and pH, on the MB removal efficiency, were investigated. The presence of Ag on the ZnO structure resulted in superior catalytic activity compared to the pure ZnO sample. High removal efficiency for MB, corresponding to 95%, was obtained in 30 min of reaction time only, using Ag-doped ZnO NPs. This result can be related to its smaller bandgap energy (1.92 eV) when compared to the ZnO sample (2.85 eV). The material presented a satisfactory level of reusability after three consecutive cycles. In addition, a reaction mechanism for MB photodegradation onto Ag-doped ZnO NPs under sunlight irradiation was suggested. Overall, the catalyst prepared via the green route in this work exhibited excellent photocatalytic activity under sunlight for MB degradation in an aqueous solution.