Coral-Like LaNixFe1-xO3 Perovskite Catalyst for High-Performance Oxygen Evolution Reaction

With the rare earth element La was selected as the A site and transition metal ions (Ni, Fe) as the B site of perovskite-type oxides with general formula ABO3, a series of LaNixFe1-xO3 (x=0, 0.3, 0.5, 0.7, 0.8, 1.0) perovskite catalysts were prepared by sol-gel method to investigate their catalytic performance for oxygen evolution reaction (OER). The catalyst activity was screened by linear scanning cyclic voltammetry (LSV), Tafel curves, and electrochemical impedance spectroscopy (EIS). A group of electrochemical tests for LaNixFe1-xO3 with various Ni/Fe ratios indicate that LaNi0.8Fe0.2O3 catalyst exhibits excellent electrochemical activity, with a resistance to charge-transfer reaction (Rct) of 5.942 Ω cm-2, overpotential of 391 mV, a Tafel slope of 102.8 mV dec-1, and electrochemical double-layer capacitance (Cdl) of 12.31 mF cm-1. The stability test after 15000 s proves that the optimized LaNi0.8Fe0.2O3 has better stability compared to pristine LaFeO3 and LaNiO3. In addition, LaNi0.8Fe0.2O3 also exhibits the largest electrochemical active area (ECSA=307.75 cm2) and exchange current density (jo=1.08 mA cm-2). This work provides reference for perovskite in improving oxygen evolution performance.

Spectrophotometric assay of Nicotinamide in Pharmaceutical Dosages

The reaction of nicotinamide and alizarin reagent using charge transfer reaction at a pH of 5.54 lead to produce a red colored compound measured at 527 nm., while the blue colored complex was formed using the oxidation reduction reaction between nicotinamide and chromate at pH 3.49 in the presence of an indigo cochineal dye. Theses tow colored products were measured at 527 and 610 nm respectively using two simple, fast and an accurate spectrophotometric methods. The linearity of the charge transfer method was followed Beer’s law 0.4 - 32 μg while the oxidation reduction method was obeyed Beer’s law from 1.6 - 40 μg in depending on the concentration range. Molar absorptivity was 1.95×104 and 2.16×104 mol−1 cm−1 for the red and blue colored complex respectively. Finally, the values of Sandal’s sensitivity were 0.00626 and 0.00565 μg−2 cm−1 for the first and second methods respectively. These two methods have been applied to quantify the amount of nicotinamide in pharmaceuticals with good recovery.

Theory of Charge Transfer Reaction Process at the Sensitizers Molecule Dye N3 Contact with MgO Semiconductor

A theoretical charge transport rate approach has taken to study the charge transfer properties in non-homogeneous N3-MgO systems. It develops at the fully quantum transition theory by means of transition energy, potential, driving energy and coupling constant. It is obtained that transition energy is determined by the donor acceptor scenario, dependent on the radii of N3 and MgO, dielectric constant and refractive index of solvents. The transition energy of charge carriers increased with increased dielectric constant and decreased refractive index of solvents. Transition energy of N3-MgO system reach to top with methanol (0.582 ev) and has minimum with Chlorobenzene (0.104eV). Dependences of the driving energy versus chemical potential of N3 dye and conduction band of semiconductor with potential barrier, the charge transfer rate are increased with decreased driving force of system. It is established that increased coupling constant factor reduces to increased charge transfer rate.

Kinetic properties of sodium-ion transfer at the interface between graphitic materials and organic electrolyte solutions

Graphitic materials cannot be applied for the negative electrode of sodium-ion battery because the reversible capacities of graphite are anomalously small. To promote electrochemical sodium-ion intercalation into graphitic materials, the interfacial sodium-ion transfer reaction at the interface between graphitized carbon nanosphere (GCNS) electrode and organic electrolyte solutions was investigated. The interfacial lithium-ion transfer reaction was also evaluated for the comparison to the sodium-ion transfer. From the cyclic voltammograms, both lithium-ion and sodium-ion can reversibly intercalate into/from GCNS in all of the electrolytes used here. In the Nyquist plots, the semi-circles at the high frequency region derived from the Solid Electrolyte Interphase (SEI) resistance and the semi-circles at the middle frequency region owing to the charge-transfer resistance appeared. The activation energies of both lithium-ion and sodium-ion transfer resistances were measured. The values of activation energies of the interfacial lithium-ion transfer suggested that the interfacial lithium-ion transfer was influenced by the interaction between lithium-ion and solvents, anions or SEI. The activation energies of the interfacial sodium-ion transfer were larger than the expected values of interfacial sodium-ion transfer based on the week Lewis acidity of sodium-ion. In addition, the activation energies of interfacial sodium-ion transfer in dilute FEC-based electrolytes were smaller than those in concentrated electrolytes. The activation energies of the interfacial lithium/sodium-ion transfer of CNS-1100 in FEC-based electrolyte solutions were almost the same as those of CNS-2900, indicating that the mechanism of interfacial charge-transfer reaction seemed to be the same for highly graphitized materials and low-graphitized materials each other. Graphic abstract

Nanoparticle and Surfactant Controlled Switching between Proton Transfer and Charge Transfer Reaction Coordinates

The reaction coordinates of a molecular photo-switch 2-(4′-diethylamino-2′-hydroxyphenyl)-1H-imidazo-[4,5-b]pyridine (DHP) was tuned with nanoparticle and surfactant. DHP undergoes ESIPT and emits normal and tautomer emissions in N,N-dimethylformamide. Silver nanoparticle supresses the...