Boosting CO2 Electroreduction on N,P-Co-doped Carbon Aerogels

Electroreduction of CO₂ to CO powered by renewable electricity is a possible alternative to synthesizing CO from fossil fuel. However, it is very hard to achieve high current density at high faradaic efficiency (FE). Here, the first use of N,P-co-doped carbon aerogels (NPCA) to boost CO₂ reduction to CO is presented. The FE of CO could reach 99.1 % with a partial current density of −143.6 mA cm⁻², which is one of the highest current densities to date. NPCA has higher electrochemical active area and overall electronic conductivity than that of N- or P-doped carbon aerogels, which favors electron transfer from CO₂ to its radical anion or other key intermediates. By control experiments and theoretical calculations, it is found that the pyridinic N was very active for CO₂ reduction to CO, and co-doping of P with N hinder the hydrogen evolution reaction (HER) significantly, and thus the both current density and FE are very high.     

Physicochemical and functional characteristics of radiation-processed shrimp chitosan

The effects of gamma irradiation on chitosan samples were determined in terms of physicochemical and functional properties. Shrimp chitosan was extracted from shell using a chemical process involving demineralization, deproteinization, decolorization and deacetylation. Commercial snow chitosan was also used. Samples (in a solid state) were given irradiation dose of 25 kGy at a dose rate of 1.1013 kGy/h in air and 0 kGy samples were used as controls. Results showed that moisture contents were between 8.690% and 13.645%. There were no significant differences (P>0.05) in the degree of deacetylation of the chitosan samples. Significant differences (P<0.05) were observed in the viscosity and viscosity-average molecular weight of the chistosan samples. Viscosity and molecular weight decreased when the samples were given the irradiation dose of 25 kGy. Chitosan samples had low antioxidant activity compared with BHT. Water binding capacity ranged from 582.40% to 656.75% and fat binding capacity was between 431.00% and 560.55%. Irradiation had a major effect on the viscosity and the viscosity-average molecular weight of the chitosan samples.     

Effect of grinding on the photo and electroluminescence of ZnO electroluminophores

Grinding of ZnO electroluminophores causes changes in integral intensity, the intensity of different peaks and the peak positions of spectral curves of photo (PL) and electroluminescence (EL). These results are explained in terms of (i) destruction of EL barrier and (ii) location of different luminescent centres in terms of coherent domains.The autors are thankful to Dr. R. K. Thakur for his encouragement and to University Grants Commission for awarding a Teacher Fellowship to one of them (RPA).     

Low Temperature Studies on the Grain-Size Effect on the Electro-optical Properties of ZnO Luminophores

The electroluminescence and photoluminescence of the self-activated ZnO luminophores exhibit three prominent bands in the green, yellow and Yellow-orange regions. With the reduction in grain size, these bands shift towards lower energy side and their energies are enhanced. The bands shift towards lower energy side with decreasing temperature of the luminophores. Both the electroluminescence and photoluminescence have maximum overall brightness for 33 micron grain size. One additional peak at 120 °K is found during the brightness studies of electroluminescence and photoluminescence of the luminophores. The appearence of such an additional peak is also confirmed from the studies of the brightness waves. The effects of grain size on the electro-optical properties of the self-activated ZnO luminophores are discussed on the basis of the existing ideas about photo- and electroluminescence.     

3D Nitrogen-Doped Graphene Encapsulated Metallic Nickel–Iron Alloy Nanoparticles for Efficient Bifunctional Oxygen Electrocatalysis

It is extremely desirable to explore high-efficient, affordable and robust oxygen electrocatalysts toward rechargeable Zn–air batteries (ZABs). A 3D porous nitrogen-doped graphene encapsulated metallic Ni₃Fe alloy nanoparticles aerogel (Ni₃Fe-GA₁) was constructed through a facile hydrothermal assembly and calcination process. Benefiting from 3D porous configuration with great accessibility, high electrical conductivity, abundant active sites, optimal nitrogen content and strong electronic interactions at the Ni₃Fe/N-doped graphene heterointerface, the obtained aerogel showed outstanding catalytic performance toward the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Specifically, it exhibited an overpotential of 239 mV to attain 10 mA cm⁻² for OER, simultaneously providing a positive onset potential of 0.93 V within a half-wave potential of 0.8 V for ORR. Accordingly, when employed in the aqueous ZABs, Ni₃Fe-GA₁ achieved higher power density and superior reversibility than Pt/C−IrO₂ catalyst, making it a potential candidate for rechargeable ZABs.     

Energy calculations of 6-mercaptopurine riboside adsorbed on a silver electrode surface using density functional theory

The normal Raman and surface enhanced Raman scattering spectra were obtained for 6-mercaptopurine riboside. The mode of interaction between 6-MPR and an adatom on a silver electrode surface was studied using density functional theory calculations. Two functionals, B3LYP and DVWN, were used in the analysis. The calculations were performed on the ionized and non-ionized forms of 6-MPR, with the silver ions attached to the three possible coordination sites, N1, N3 and N7 of the molecule. The analysis was performed based on the zero-point-energy as well as adsorption and solvation energies. Results of the B3LYP and DVWN calculations were consistent and established that coordination through the N7 of 6-MPR was the most energetically favorable of the three coordination sites. The analysis was unable to determine, with a high degree of accuracy, whether the molecule adsorbs on the surface in its non-ionized or ionized form.     

Synthesis and characterization of Ce doped silica (SiO2) nanoparticles

A series of silica doped with different mol percentages of Ce³⁺ concentration was synthesized using a sol-gel method to determine the dependence of photoluminescence wavelengths and intensity on the concentrations of the dopants. Sol-gel glasses are porous networks that have been densified through chemical processing and heat treatment. Rare-earths (REs) are insoluble in silica; due to this insolubility RE ions in silicate glasses enter as network modifiers and compete for non-bridging oxygen in order to complete their coordination. The morphological, structural, thermal and optical properties of the phosphors were characterized by X-ray diffraction, scanning electron microscopy, UV-vis absorption, photoluminescence, thermogravimetric analyses and differential scanning calorimeter. Silica (SiO₂) gel containing Ce³⁺ ions was sputter coated with Au (gold) in order to monitor surface morphology of the samples. The highest emission intensity was found for the sample with a composition of 0.5 mol% Ce³⁺. Cerium doped silica glasses had broad blue emission corresponding to the ²D_3/2-²F_J transition at 448 nm but exhibited apparent concentration quenching above concentrations of 0.5 mol% Ce³⁺.