In-situ electrochemical modification of pre-intercalated vanadium bronze cathodes for aqueous zinc-ion batteries

Vanadium bronzes have been well-demonstrated as promising cathode materials for aqueous zinc-ion batteries. However, conventional single-ion pre-intercalated V2O5 nearly reached its energy/power ceiling due to the nature of micro/electronic structures and unfavourable phase transition during Zn2+ storage processes. Here, a simple and universal in-situ anodic oxidation method of quasi-layered CaV4O9 in a tailored electrolyte was developed to introduce dual ions (Ca2+ and Zn2+) into bilayer δ-V2O5 frameworks forming crystallographic ultra-thin vanadium bronzes, Ca0.12Zn0.12V2O5·nH2O. The materials deliver transcendental maximum energy and power densities of 366 W h kg−1 (478 mA h g−1 @ 0.2 A g−1) and 6627 W kg−1 (245 mA h g−1 @ 10 A g−1), respectively, and the long cycling stability with a high specific capacity up to 205 mA h g−1 after 3000 cycles at 10 A g−1. The synergistic contributions of dual ions and Ca2+ electrolyte additives on battery performances were systematically investigated by multiple in-/ex-situ characterisations to reveal reversible structural/chemical evolutions and enhanced electrochemical kinetics, highlighting the significance of electrolyte-governed conversion reaction process. Through the computational approach, reinforced “pillar” effects, charge screening effects and regulated electronic structures derived from pre-intercalated dual ions were elucidated for contributing to boosted charge storage properties.

A Simple g-C3N4/TNTs Heterojunction for Improving the Photoelectrocatalytic Degradation of Methyl Orange

In this work, highly ordered titanium dioxide nanotube arrays (TNTs) were first prepared by anodic oxidation method. Then, g-C3N4/TNTs heterojunctions were prepared by ultrasonically loading graphitic carbon nitride (g-C3N4) onto the TNTs. The morphology and crystal structure of TNTs and g-C3N4/TNTs were characterized by SEM and XRD. The photoelectrocatalytic (PEC) degradation of methyl orange (MO) by TNTs and g-C3N4/TNTs was studied in a PEC degradation system. The photocatalytic (PC), electrocatalytic (EC), and PEC degradation properties were compared, and the effect of pollutant concentration on the degradation performance of the catalysts was analyzed. According to the experimental results, the degradation rate of MO with TNTs only reaches 65.1% after 120 min, while the degradation rate of MO with g-C3N4/TNTs reaches 84.6% in the same time. Due to the synergistic effect of light and electricity, the PEC degradation efficiency of the two catalysts is greater than the sum of PC and EC degradation, proving that g-C3N4/TNTs heterojunctions provide excellent PEC performance for the degradation of MO.

Determination of chemical oxygen demand in mixed organic solution by Ti/TiO2 nanotube array electrode method

Chemical oxygen demand (COD) is a significant parameter for analyzing water quality. However, the detection methods still suffer from the problems of secondary pollution, use of harmful substances, complicated operations, etc. To trace these problems, a Ti/TiO2 nanotube array (NTA) electrode was successfully prepared by the secondary anodic oxidation method in this work. The prepared electrode was used to determine COD of single- and multi-component solutions (including aniline, rhodamine B, and potassium hydrogen phthalate). The Ti/TiO2 NTA electrode exhibited higher electrochemical oxidation efficiency than the neat Ti one. The electrocatalytic reactions of the target organics on the electrode surface were confirmed to conform to the first-order kinetic process. Within COD range of 5–150 mg/L, COD value was not only proportional to the anodizing current but also related to organic matter itself. The activation energies of electro-oxidation reaction of different substances were different from each other (An: 14.25 kJ/mol, RhB: 18.56 kJ/mol, and KHP: 35.32 kJ/mol), indicating the differences in their dynamic behaviors on the electrode surface. The related bias obtained for all successive measurements was below ± 5.8%. Therefore, we report a fast, effective, accurate, and well-reproducible COD detection method, which is feasible for both single-component and multiple-component organic solutions.

Recent Progress in Anodic Oxidation of TiO2 Nanotubes and Enhanced Photocatalytic Performance: A Short Review

By adjusting the oxidation voltage, electrolyte, anodizing time and other parameters, TiO2 nanotubes with high aspect ratio can be prepared by oxidation in organic system because anodic oxidation method has the advantage of simple preparation process, low material cost and controllable morphology. This review focusses on the influence of anodizing parameters on the morphology of TiO2 nanotube arrays prepared by anodizing. In order to improve the photocatalytic activity of TiO2 nanotubes under visible light and to prolong the life of photo-generated carriers, the research status of improving the photocatalytic activity of TiO2 nanotubes in recent years is reviewed. This review focusses on the preparation and modification of TiO2 nanotubes by anodic oxidation, which is helpful to understand the best structure of TiO2 nanotubes and the appropriate modification methods, thus guiding the application of TiO2 nanotubes in practical photocatalysis. Finally, the development of TiO2 nanotubes is prospected.

Energetic Films Realized by Encapsulating Copper Azide in Silicon-Based Carbon Nanotube Arrays with Higher Electrostatic Safety

Since copper azide (Cu(N3)2) has high electrostatic sensitivity and is difficult to be practically applied, silicon-based Cu(N3)2@carbon nanotubes (CNTs) composite energetic films with higher electrostatic safety were fabricated, which can be compatible with micro-electro mechanical systems (MEMS). First, a silicon-based porous alumina film was prepared by a modified two-step anodic oxidation method. Next, CNTs were grown in pores of the silicon-based porous alumina film by chemical vapor deposition. Then, copper nanoparticles were deposited in CNTs by electrochemical deposition and oxidized to Cu(N3)2 by gaseous hydrogen azide. The morphology and composition of the prepared silicon-based Cu(N3)2@CNTs energetic films were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD), respectively. The electrostatic sensitivity of the composite energetic film was tested by the Bruceton method. The thermal decomposition kinetics of the composite energetic films were studied by differential scanning calorimetry (DSC). The results show that the exothermic peak of the silicon-based Cu(N3)2@CNTs composite energetic film is at the temperature of 210.95 °C, its electrostatic sensitivity is significantly less than that of Cu(N3)2 and its 50% ignition energy is about 4.0 mJ. The energetic film shows good electric explosion characteristics and is successfully ignited by laser.

Platinum and Iridium Oxide Co-modified TiO2 Nanotubes Array Based Photoelectrochemical Sensors for Glutathione

Oriented TiO2 nanotubes, which are fabricated by anodic oxidation method, are prospective in photoelectrochemical analysis and sensors. In this work, Pt and IrO2 co-modified TiO2 nanotubes array was prepared via a two-step deposition process involving the photoreductive deposition of Pt and chemical deposition of IrO2 on the oriented TiO2 nanotubes. Due to the improved separation of photo-generated electrons and holes, Pt-IrO2 co-modified TiO2 nanotubes presented significantly higher PEC activity than pure TiO2 nanotubes or mono-modified TiO2 nanotubes. The PEC sensitivity of Pt-IrO2 co-modified TiO2 nanotubes for glutathione was also monitored and good sensitivity was observed.