Ag and CdS nanoparticles co-sensitized TiO2 nanotubes for enhancing visible photoelectrochemical performance

NH4V4O10 nanobelts vertically grown on 3D TiN nanotube arrays as high-performance electrode materials of supercapacitors

High performance supercapacitor without binders has attracted wide attention as an energy storage device. In this work, novel NH4V4O10 nanobelts were successfully synthesized and decorated into TiN nanotube arrays by a simple hydrothermal method. The as-prepared no-binder electrode hybrids exhibited excellent electrochemical performances with a specific capacitance of 749.0 F g-1 at 5 mV s-1 and a capacity retention of 85.7% after 200 cycles, which makes it an appealing candidate for electrode materials of supercapacitors.

Influence of the Silver Nanoparticles (AgNPs) Formation Conditions onto Titanium Dioxide (TiO2) Nanotubes Based Electrodes on Their Impedimetric Response

This paper presents the comparison of the effects of three methods of production of silver spherical and near-spherical nanoparticles (AgNPs) on the titanium dioxide nanotubes (TNT) base: cyclic voltammetry, chronoamperometry, and sputter deposition. It also evaluates the influence of silver nanoparticles on the electrochemical properties of the developed electrodes. The novelty of this research was to fabricate regular AgNPs free of agglomerates uniformly distributed onto the TNT layer, which has not been accomplished with previous attempts. The applied methods do not require stabilizing and reducing reagents. The extensive electrochemical characteristic of AgNP/TNT was performed by open circuit potential and electrochemical impedance spectroscopy methods. For AgNPs/TNT obtained by each method, the impedance module of these electrodes was up to 50% lower when compared to TNT, which means that AgNPs enabled more efficient electron transfer due to the effective area increase. In addition, the presence of nanoparticles increases the corrosion resistance of the prepared electrodes. These substrates can be used as electrochemical sensors due to their high electrical conductivity, and also as implants due to the antibacterial properties of both the TNT and AgNPs.

Enhanced Photocatalytic Performance of Nitrogen-Doped TiO₂ Nanotube Arrays Using a Simple Annealing Process

Nitrogen-doped TiO₂ nanotube arrays (N-TNAs) were successfully fabricated by a simple thermal annealing process in ambient N₂ gas at 450 °C for 3 h. TNAs with modified morphologies were prepared by a two-step anodization using an aqueous NH₄F/ethylene glycol solution. The N-doping concentration (0–9.47 at %) can be varied by controlling N₂ gas flow rates between 0 and 500 cc/min during the annealing process. Photocatalytic performance of as-prepared TNAs and N-TNAs was studied by monitoring the methylene blue degradation under visible light (λ ≥ 400 nm) illumination at 120 mW·cm⁻². N-TNAs exhibited appreciably enhanced photocatalytic activity as compared to TNAs. The reaction rate constant for N-TNAs (9.47 at % N) reached 0.26 h⁻¹, which was a 125% improvement over that of TNAs (0.115 h⁻¹). The significant enhanced photocatalytic activity of N-TNAs over TNAs is attributed to the synergistic effects of (1) a reduced band gap associated with the introduction of N-doping states to serve as carrier reservoir, and (2) a reduced electron‒hole recombination rate.

Cr(VI) remediation from aqueous environment through modified-TiO2-mediated photocatalytic reduction

Cr(VI) exhibits cytotoxic, mutagenic and carcinogenic properties; hence, effluents containing Cr(VI) from various industrial processes pose threat to aquatic life and downstream users. Various treatment techniques, such as chemical reduction, ion exchange, bacterial degradation, adsorption and photocatalysis, have been exploited for remediation of Cr(VI) from wastewater. Among these, photocatalysis has recently gained considerable attention. The applications of photocatalysis, such as water splitting, CO2 reduction, pollutant degradation, organic transformation reactions, N2 fixation, etc., towards solving the energy crisis and environmental issues are briefly discussed in the Introduction of this review. The advantages of TiO2 as a photocatalyst and the importance of its modification for photocatalytic reduction of Cr(VI) has also been addressed. In this review, the photocatalytic activity of TiO2 after modification with carbon-based advanced materials, metal oxides, metal sulfides and noble metals towards reduction of Cr(VI) was evaluated and compared with that of bare TiO2. The photoactivity of dye-sensitized TiO2 for reduction of Cr(VI) was also discussed. The mechanism for enhanced photocatalytic activity was highlighted and attributed to the resultant properties, namely, effective separation of photoinduced charge carriers, extension of the light absorption range and intensity, increase of the surface active sites, and higher photostability. Advantages and limitations for photoreduction of Cr(VI) over modified TiO2 are depicted in the Conclusion. The various challenges that restrict the technology from practical applications in remediation of Cr(VI) from wastewater were addressed in the Conclusion section as well. The future perspectives of the field presented in this review are focused on the development of whole-solar-spectrum responsive, TiO2-coupled photocatalysts which provide efficient photocatalytic reduction of Cr(VI) along with their good recoverability and recyclability.

CdS quantum dots confined in mesoporous TiO2 with exceptional photocatalytic performance for degradation of organic polutants

In this paper, the mesoporous TiO₂ with different concentration of CdS quantum dots (i.e., x% CdS/TiO₂) was successfully fabricated by the sol-gel method. The composition, structure and morphology of the nanocomposites were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), UV-vis diffuse reflectance spectroscopy (UV-Vis/DRS) and nitrogen physical adsorption test and so on. The proportion of CdS and TiO₂ is very important for the photocatalytic performance. As a result, the photocatalytic degradation performance from the most to the least is in the order of 2% CdS/TiO₂, 4% CdS/TiO₂, 8% CdS/TiO₂, pure TiO₂ and 1% CdS/TiO₂. The photocatalytic (PC) activity of the 2% CdSTiO₂ is characterized by photocatalytic degradation of methyl orange, which can be completely degraded within 45 min better than 60 min TiO₂ takes. It is also much better than CdS. Moreover, other four organic pollutants, such as methylthionine chloride, bisphenol A, rhodamine B, malachite green can also be degraded quickly on the condition of 2% CdS/TiO₂. What's more, the chemical stability and cycling capability of 2% CdS/TiO₂ are reflected by five cyclic degradation of methyl orange.

MnO2 modified TiN nanotube arrays on Ti mesh for flexible supercapacitors electrode

The vertically grown TiN nanotube arrays maintain the structural integrity during cycling process and dramatically enhance faradic reaction of MnO₂ by offering superhighways for electrons and ions transport.

Charge Transport in Two-Photon Semiconducting Structures for Solar Fuels

Semiconducting heterostructures are emerging as promising light absorbers and offer effective electron-hole separation to drive solar chemistry. This technology relies on semiconductor composites or photoelectrodes that work in the presence of a redox mediator and that create cascade junctions to promote surface catalytic reactions. Rational tuning of their structures and compositions is crucial to fully exploit their functionality. In this review, we describe the possibilities of applying the two-photon concept to the field of solar fuels. A wide range of strategies including the indirect combination of two semiconductors by a redox couple, direct coupling of two semiconductors, multicomponent structures with a conductive mediator, related photoelectrodes, as well as two-photon cells are discussed for light energy harvesting and charge transport. Examples of charge extraction models from the literature are summarized to understand the mechanism of interfacial carrier dynamics and to rationalize experimental observations. We focus on a working principle of the constituent components and linking the photosynthetic activity with the proposed models. This work gives a new perspective on artificial photosynthesis by taking simultaneous advantages of photon absorption and charge transfer, outlining an encouraging roadmap towards solar fuels.

Cu2O sensitized flexible 3D-TiO2 nanotube arrays for enhancing visible photo-electrochemical performance

Cu₂O flake and nanoparticle modified 3D-TiO₂ nanotube arrays were firstly prepared by electrochemical deposition. The growth process of Cu₂O is discussed. A mechanism is proposed to explain the difference in photocurrent response and photo-catalytic activity.

Hydrothermal synthesis of novel BiFeO3/BiVO4 heterojunctions with enhanced photocatalytic activities under visible light irradiation

BiFeO₃/BiVO₄ heterojunction photocatalysts were synthesized by a hydrothermal method.

One pot microwave-assisted synthesis of Ag decorated yolk@shell structured TiO2 microspheres

A facile and extremely fast one-pot microwave-assisted synthesis of Ag decorated yolk@shell structured TiO₂ microspheres was reported.