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Spinel materials are attractive to photocatalytic degradation of contaminants. In this study, strontium (Sr) doped spinel cobalt chromite (CoCr 2 O 4) was synthesized by solution combustion method and characterized using techniques such as X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and electrochemical impedance spectroscopy (EIS). 30 -50 nm-cubic CoCr 2 O 4 nanocrystals were obtained, and phase transitions of CoO 6 →CoO 4 and CrO 4 →CrO 6 occurred as the Sr doping content increased until 0.6 % Sr doped sample displayed an inverse spinel phase. The modifications in composition and structure induced the co-existence of multivalent states for Co and Cr, which in turn changed the optical, complex impedance, and magnetic spin state of CoCr 2 O 4. The 0.6 % Sr-doped sample showed the highest photocatalytic efficiency of 93 % due to enhanced optical absorption, reduced energy band gap, oxygen vacancies formation, and a high spin state of Co. The XRD structure and photocatalytic activity remained stable even after five cycles without any leakage of metal elements. The degradation pathway and Mott-Schottky curves were employed to elucidate the mechanism behind this enhancement. The strategy employed in this study proved effective, and the synthesized materials show promise for the photocatalytic degradation of contaminants. [ABSTRACT FROM AUTHOR]

The PTCR effect is an important application phenomenon in the ferroelectric BaTiO 3 electronic ceramic materials. In this work, the PTCR effect is also found in high pressure (HP) hot quenched Ca 1-x Y x Cu 3 Ti 4 O 12 (CYCTO) ceramics. Compared with the pure CaCu 3 Ti 4 O 12 (CCTO) ceramic synthesized under ordinary pressure (OP), the low temperature resistivity of HP CYCTO samples is about 3 orders of magnitude lower than that of untreated CCTO samples, showing an obvious PTCR effect. The transition temperature is close to 178 K for x = 0.2 sample. The analysis of crystal and magnetic structures shows that the crystal and magnetic structures of HP CYCTO samples do not change before and after the resistance transition. X-ray photoelectron spectroscopy showed that the concentration of oxygen vacancy defects in HP CYCTO is higher than CCTO. By analyzing the conduction behaviors of HP CYCTO samples, it suggests that oxygen vacancies and Y3+ ions may be the important donors for the decrease of low temperature resistivity of HP CYCTO samples. The results in this work have important reference value for the application of the electrical conduction behaviors in CCTO. [ABSTRACT FROM AUTHOR]

Abstract: A free-standing SnO2/reduced graphene oxide (re-G) hybrid paper has been successfully fabricated by a facile vacuum filtration approach through a uniformly dispersed SnO2 nanoparticle and graphene oxide mixed solution. As potential anode material for high power and energy applications, the hybrid nanostructures were directly evaluated as anode for rechargeable lithium ion batteries without adding any polymer binder, conductive additives or current collectors. And the composite exhibits a greatly enhanced synergic effect with extremely high energy storage stability of 700mAhg−1 after 100 cycles benefiting from the advanced structural features. [Copyright &y& Elsevier]

Abstract: We have successfully fabricated the enhanced 3D hierarchical double porous Co3O4/graphene architecture by employing a simple, facile and inexpensive microwave-assisted method. The ultimately formed hierarchical porous configuration can provide more rapid electrolyte diffusion to the active materials due to macro- and micro-porosity. The Co3O4 nanoparticles (NPs), which are homogeneously distributed on graphene sheets, showed high reversible capacities as well as significantly enhanced cycling performance and high rate capabilities when evaluated as anode for lithium ion battery. The superior performance could be attributed to the unique enhanced 3D hierarchical double porous architecture. Our results opened a new doorway to prepare novel anode architecture for high performance lithium ion batteries. [Copyright &y& Elsevier]