Cyclic voltammetry studies of TiO2 nanotube arrays electrode: Conductivity and reactivity in the presence of H+ and aqueous redox systems

Electrospun network based on polyacrylonitrile-polyphenyl/titanium oxide nanofibers for high-performance supercapacitor device

Nanofibers and mat-like polyacrylonitrile-polyphenyl/titanium oxide (PAN-Pph./TiO2) with proper electrochemical properties were fabricated via a single-step electrospinning technique for supercapacitor application. Scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), thermogravimetry (TGA), fourier transform infrared (FTIR), X-ray diffraction (XRD) and energy dispersive X-ray (EDX) were conducted to characterize the morphological and chemical composition of all fabricated nanofibers. Furthermore, the electrochemical activity of the fabricated nanofibers for energy storage applications (supercapacitor) was probed by cyclic voltammetry (CV), charge-discharge (CD), and electrochemical impedance spectroscopy (EIS). The PAN-PPh./TiO2 nanofiber electrode revealed a proper specific capacitance of 484 F g-1 at a current density of 11.0 A g-1 compared with PAN (198 F g-1), and PAN-PPh. (352 F g-1) nanofibers using the charge-discharge technique. Furthermore, the PAN-PPh./TiO2 nanofiber electrode displayed a proper energy density of 16.8 Wh kg-1 at a power density (P) of 2749.1 Wkg-1. Moreover, the PAN-PPh./TiO2 nanofiber electrode has a low electrical resistance of 23.72 Ω, and outstanding cycling stability of 79.38% capacitance retention after 3000 cycles.

Tailoring the density of states of Ni(OH)2 with Ni0 towards solar urea wastewater splitting

Solar urea wastewater splitting is capable of producing hydrogen and degrading the urea pollutant simultaneously. Nickel hydroxide (Ni(OH)2) has been recognized as an effective cocatalyst for the urea oxidation reaction (UOR). But the lack of an efficient preparation method and a suitable Ni(OH)2 based cocatalyst limits the performances of solar urea wastewater splitting. Herein, a potential-cycling method is developed with a high-purity nickel plate serving as the counter electrode and nickel source in a three-electrode configuration. Spherical Ni0-doped Ni(OH)2 nanoparticles are successfully synthesized on the surface of TiO2 nanorod arrays. The photocurrent density of TiO2/Ni0:Ni(OH)2 can reach 0.56 mA cm-2 at 1.23 VRHE in 1 M NaOH and 0.33 M CO(NH2)2 mixed electrolyte under AM1.5G illumination, which is 1.75 and 1.93 times those of TiO2/Ni(OH)2 deposited using a normal potentiostatic method with nickel salt solution and pristine TiO2, respectively. Ni0 doping can significantly decrease the charge transfer resistance and provide a more favorable distribution of density of states of Ni(OH)2 for the UOR. Furthermore, Ni0:Ni(OH)2 decorated TiO2 photoanodes exhibit good photocurrent retention during 12 h continuous testing. This work expands the preparation technique of urea catalysts and the strategy for developing highly efficient nickel-based catalysts.

TiO2/MWCNT/Nafion-Modified Glassy Carbon Electrode as a Sensitive Voltammetric Sensor for the Determination of Hydrogen Peroxide

In this work we describe a straightforward approach for creating a nanocomposite comprising multiwalled carbon nanotubes (MWCNTs) and titanium dioxide (TiO2) using the hydrothermal technique, which is then characterized by scanning electron microscope (SEM), energy-dispersive X-ray spectrometer (EDS), X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), and thermal gravimetric analysis (TGA) to assess its properties. Nafion is employed as a reticular agent for the nanocomposite on the glassy carbon electrode (GCE), creating the MWCNT/TiO2/Nafion/GCE system. The electrochemical behavior of the system was evaluated using cyclic voltammetry, revealing its remarkable electrocatalytic activity for detecting hydrogen peroxide in water. The developed sensor showcased a broad linear response range of 14.00 to 120.00 μM, with a low detection limit of 4.00 μM. This electrochemical sensor provides a simple and highly sensitive method for detecting hydrogen peroxide in aqueous solutions and shows promising potential for various real-world applications, particularly in H2O2 monitoring.

Meniscus-Guided Micro-Printing of Prussian Blue for Smart Electrochromic Display

Using energy-saving electrochromic (EC) displays in smart devices for augmented reality makes cost-effective, easily producible, and efficiently operable devices for specific applications possible. Prussian blue (PB) is a metal-organic coordinated compound with unique EC properties that limit EC display applications due to the difficulty in PB micro-patterning. This work presents a novel micro-printing strategy for PB patterns using localized crystallization of FeFe(CN)₆ on a substrate confined by the acidic-ferric-ferricyanide ink meniscus, followed by thermal reduction at 120 °C, thereby forming PB. Uniform PB patterns can be obtained by manipulating printing parameters, such as the concentration of FeCl₃ ·K₃ Fe(CN)₆ , printing speed, and pipette inner diameter. Using a 0.1 M KCl (pH 4) electrolyte, the printed PB pattern is consistently and reversibly converted to Prussian white (CV potential range: -0.2-0.5 V) with 200 CV cycles. The PB-based EC display with a navigation function integrated into a smart contact lens is able to display directions to a destination to a user by receiving GPS coordinates in real time. This facile method for forming PB micro-patterns could be used for advanced EC displays and various functional devices.

Scalable Route toward Superior Photoresponse of UV-Laser-Treated TiO2 Nanotubes

Titanium dioxide nanotubes gain considerable attention as a photoactive material due to chemical stability, photocorrosion resistance, or low-cost manufacturing method. This work presents scalable pulsed laser modification of TiO₂ nanotubes resulting in enhanced photoactivity in a system equipped with a motorized table, which allows for modifications of both precisely selected and any-large sample area. Images obtained from scanning electron microscopy along with Raman and UV-vis spectra of laser-treated samples in a good agreement indicate the presence of additional laser-induced shallow states within band gap via degradation of crystalline structure. However, X-ray photoelectron spectroscopy spectra revealed no change of chemical nature of the modified sample surface. Photoelectrochemical measurements demonstrate superior photoresponse of laser-treated samples up to 1.45-fold for an energy beam fluence of 40 mJ/cm² compared to that of calcined one. According to the obtained results, optimal processing parameters were captured. Mott-Schottky analysis obtained from impedance measurements indicates an enormous (over an order of magnitude) increase of donor density along with a +0.74 V positive shift of flat band potential. Such changes in electronic structure are most likely responsible for enhanced photoactivity. Thus, the elaborated method of laser nanostructuring can be successfully employed to the large-scale modification of titania nanotubes resulting in their superior photoactivity. According to that, the results of our work provide a contribution to wider applications of materials based on titania nanotubes.

Enhanced photoelectrochemical and photocatalytic performance of iodine-doped titania nanotube arrays

The paper discusses the synthesis and performance of iodine doped titania nanotube arrays exhibited under irradiation.