Zeolite-Y encapsulated VO[2-(2′hydroxyphenyl)benzimidazole] complex: investigation of its catalytic activity towards oxidation of organic substrates

Zeolite-Y encapsulated VO(IV)2-(2′-hydroxyphenyl)benzimidazole (ohpbmzl) was synthesized by flexible ligand approach and characterized using various physico-chemical techniques such as elemental analysis, XRD, inductively coupled plasma-atomic emission, fourier transform infrared spectroscopy, UV–vis-diffuse reflectance and electron paramagnetic resonance spectroscopy, thermogravimetric analysis, BET surface area and cyclic voltammetry (CV). Based on the results a square pyramidal structure was suggested for the encapsulated complex. Shift in UV absorbance to higher wavelength and variations in the redox potential values compared to the non-encapsulated complex in CV confirmed the successful encapsulation of the complex in the zeolite matrix. The catalytic efficacy was investigated towards oxidation of phenol, styrene, cyclohexane and ethyl benzene in acetonitrile using H2O2 as oxidant. Influence of reaction parameters like catalyst and substrate concentration, substrate/H2O2 molar ratio, and temperature were investigated to optimize the reaction conditions for maximum substrate conversion and selectivity towards desired products using the encapsulated complex. The catalytic activity was compared with vanadyl exchanged zeolite-Y (VO-Y) and non-encapsulated complex. The encapsulated complex retained its stability up to 3 runs as confirmed by recycling studies. Mechanistic pathways were proposed for all the probe reactions

Electrochemical impedance studies of capacity fading of electrodeposited ZnO conversion anodes in Li-ion battery

Electrodeposited ZnO coatings suffer severe capacity fading when used as conversion anodes in sealed Li cells. Capacity fading is attributed to (i) the large charge transfer resistance, Rct (300-700 Ω) and (ii) the low Li+ ion diffusion coefficient, D+Li (10-15 to 10-13 cm2 s-1). The measured value of Rct is nearly 10 times higher and D+Li 10-100 times lower than the corresponding values for Cu2O, which delivers a stable reversible capacity. © Indian Academy of Sciences

Effect of Non-Stoichiometry on the Charge Storage Capacity of NiO Conversion Anodes in Li-Ion Batteries

Conversion anodes comprising non-stoichiometric black NiO suffer severe capacity fading in Li-ion batteries despite having a high Li+ ion diffusion coefficient. We attribute this capacity fading to (i) its small crystallite size (~ 8 nm) and (ii) high charge transfer resistance (Rct ~ 60–180 Ω cm2). Small crystallites enhance grain boundaries which promote Li+ ion diffusion without efficient material utilization. In contrast, the stoichiometric green NiO anodes deliver a stable capacity of 280 mAh g−1 over 50 charge-discharge cycles. The comparatively higher capacity of green NiO can be explained from its (i) large crystallite size (~ 104 nm) and (ii) negligible Rct values

Effect of orientation on the reversible discharge capacity of electrodeposited Cu2O coatings as lithium-ion battery anodes

Electrodeposited Cu2O coatings with 111 out-of-plane orientation were found to have the lowest reversible discharge capacity as anodes for Li-ion cells. This is attributed to the low surface energy and the consequent high thermodynamic stability of the 111 crystal face of Cu2O. In contrast, the 200 oriented coating has a higher reversible discharge capacity, owing to its polar nature and high surface energy. The highest reversible discharge capacity was observed for unoriented coatings, emphasizing the critical role played by grain boundaries in the conversion electrodes. The morphology of crystallites in the electrodes recovered after cycling is different in the three cases, suggesting that the nature of reversible chemical conversion is guided by physical attributes of the precursor Cu2O crystallites. © 2015 Springer-Verlag Berlin Heidelber