TiO2 Nanotubes Decorated with Mo2C for Enhanced Photoelectrochemical Water-Splitting Properties.

The presence of Ti3+ in the structure of TiO2 nanotube arrays (NTs) has been shown to enhance the photoelectrochemical (PEC) water-splitting performance of these NTs, leading to improved results compared to pristine anatase TiO2 NTs. To further improve the properties related to PEC performance, we successfully produced TiO2 NTs using a two-step electrochemical anodization technique, followed by annealing at a temperature of 450 °C. Subsequently, Mo2C was decorated onto the NTs by dip coating them with precursors at varying concentrations and times. The presence of anatase TiO2 and Ti3O5 phases within the TiO2 NTs was confirmed through X-ray diffraction (XRD) analysis. The TiO2 NTs that were decorated with Mo2C demonstrated a photocurrent density of approximately 1.4 mA cm-2, a value that is approximately five times greater than the photocurrent density exhibited by the bare TiO2 NTs, which was approximately 0.21 mA cm-2. The observed increase in photocurrent density can be ascribed to the incorporation of Mo2C as a cocatalyst, which significantly enhances the photocatalytic characteristics of the TiO2 NTs. The successful deposition of Mo2C onto the TiO2 NTs was further corroborated by the characterization techniques utilized. The utilization of field emission scanning electron microscopy (FESEM) allowed for the observation of Mo2C particles on the surface of TiO2 NTs. To validate the composition and optical characteristics of the decorated NTs, X-ray photoelectron spectroscopy (XPS) and UV absorbance analysis were performed. This study introduces a potentially effective method for developing efficient photoelectrodes based on TiO2 for environmentally sustainable hydrogen production through the use of photoelectrochemical water-splitting devices. The utilization of Mo2C as a cocatalyst on TiO2 NTs presents opportunities for the advancement of effective and environmentally friendly photoelectrochemical (PEC) systems.

Investigation of Performance of Anion Exchange Membrane (AEM) Electrolysis with Different Operating Conditions.

In this work, the performance of anion exchange membrane (AEM) electrolysis is evaluated. A parametric study is conducted, focusing on the effects of various operating parameters on the AEM efficiency. The following parameters-potassium hydroxide (KOH electrolyte concentration (0.5-2.0 M), electrolyte flow rate (1-9 mL/min), and operating temperature (30-60 °C)-were varied to understand their relationship to AEM performance. The performance of the electrolysis unit is measured by its hydrogen production and energy efficiency using the AEM electrolysis unit. Based on the findings, the operating parameters greatly influence the performance of AEM electrolysis. The highest hydrogen production was achieved with the operational parameters of 2.0 M electrolyte concentration, 60 °C operating temperature, and 9 mL/min electrolyte flow at 2.38 V applied voltage. Hydrogen production of 61.13 mL/min was achieved with an energy consumption of 48.25 kW·h/kg and an energy efficiency of 69.64%.

Parametric Study and Electrocatalyst of Polymer Electrolyte Membrane (PEM) Electrolysis Performance.

An investigation was conducted to determine the effects of operating parameters for various electrode types on hydrogen gas production through electrolysis, as well as to evaluate the efficiency of the polymer electrolyte membrane (PEM) electrolyzer. Deionized (DI) water was fed to a single-cell PEM electrolyzer with an active area of 36 cm2. Parameters such as power supply (50-500 mA/cm2), feed water flow rate (0.5-5 mL/min), water temperature (25-80 °C), and type of anode electrocatalyst (0.5 mg/cm2 PtC [60%], 1.5 mg/cm2 IrRuOx with 1.5 mg/cm2 PtB, 3.0 mg/cm2 IrRuOx, and 3.0 mg/cm2 PtB) were varied. The effects of these parameter changes were then analyzed in terms of the polarization curve, hydrogen flowrate, power consumption, voltaic efficiency, and energy efficiency. The best electrolysis performance was observed at a DI water feed flowrate of 2 mL/min and a cell temperature of 70 °C, using a membrane electrode assembly that has a 3.0 mg/cm2 IrRuOx catalyst at the anode side. This improved performance of the PEM electrolyzer is due to the reduction in activation as well as ohmic losses. Furthermore, the energy consumption was optimal when the current density was about 200 mA/cm2, with voltaic and energy efficiencies of 85% and 67.5%, respectively. This result indicates low electrical energy consumption, which can lower the operating cost and increase the performance of PEM electrolyzers. Therefore, the optimal operating parameters are crucial to ensure the ideal performance and durability of the PEM electrolyzer as well as lower its operating costs.

Enhancing Photoluminescence Intensity and Spectral Bandwidth of Hybrid Nanofiber/Thin-Film Multilayer Tm3+-Doped SiO2-HfO2.

Multilayering of optical thin films is widely used for a range of purposes in photonic technology, but the development of nanofiber structures that can outperform thin films and nanoparticles in optical applications cannot simply be disregarded. Hybrid structures composed of Tm3+-doped SiO2-HfO2 in the form of nanofibers (NFs) and thin films (TFs) are deposited on a single substrate using the electrospinning and dip-coating methods, respectively. Ultrafine nanofiber strands with a diameter of 10-60 nm were fabricated in both single and multilayer samples. Enhanced photoluminescence emission intensity of about 10 times was attained at wavelengths of around 457, 512 and 634 nm under an excitation of 350 nm for NF-TF-NF* hybrid structures when compared with single-layered NF and TF structures. The arrangement of nanofibers and thin films in a multilayer structure influenced the luminescence intensity and spectral bandwidth. High transparency in the range of 75-95% transparency across the wavelength of 200-2000 nm was achieved, making it ideal for photonic application. Theoretical findings obtained through IMD software were compared with experimental results, and they were found to be in good agreement.

Nata de Cassava Type of Bacterial Cellulose Doped with Phosphoric Acid as a Proton Exchange Membrane.

This work aims to encourage the use of natural materials for advanced energy applications, such as proton exchange membranes in fuel cells. Herein, a new conductive membrane produced from cassava liquid waste was used to overcome environmental pollution and the global crisis of energy. The membrane was phosphorylated through a microwave-assisted method with different phosphoric acid, (H3PO4) concentrations (10-60 mmol). Scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), dynamic mechanical analysis (DMA), swelling behavior test, and contact angle measurement were carried out on the membrane doped with different H3PO4 levels. The phosphorylated NdC (nata de cassava) membrane doped with 20 mmol (NdC20) H3PO4 was successfully modified and significantly achieved proton conductivity (maximum conductivity up to 7.9 × 10-2 S cm-1 at 80 °C). In addition, the fabricated MEA was assembled using an NdC20 membrane with 60 wt% Pt/C loading of 0.5 mg cm-2 for the anode and cathode. Results revealed that a high power density of 25 mW cm-2 was obtained at 40 °C operating temperature for a single-cell performance test. Thus, this membrane has the potential to be used as a proton exchange membrane because it is environment-friendly and inexpensive for fuel cell applications.

Vertical MoS2on SiO2/Si and Graphene: Effect of Surface Morphology on Photoelectrochemical Properties.

Two-dimensional materials have attracted intensive attention recently due to their unique optical and electronic properties and their promising applications in water splitting and solar cells. As a representative layer-structured of transition metal dichalcogenides, MoS2has attracted considerable devotion owing to its exceptional photo and electro properties. Here, we show that the chemical vapour deposition (CVD) growth of MoS2on Si photocathode and graphene/Si photocathode can be used to prepare photoelectrocatalysts for water splitting. We explore a bottom-up method to grow vertical heterostructures of MoS2and graphene by using the two-step CVD. Graphene is first grown through ambient-pressure CVD on a Cu substrate and then transferred onto SiO2/Si substrate by using the chemical wet transfer followed by the second CVD method to grow MoS2over the graphene/SiO2/Si. The effect of the growth temperatures of MoS2is studied, and the optimum temperature is 800 °C. The MoS2produced at 800 °C has the highest photocurrent density at -0.23 mA cm-2in 0.5 M Na2SO4and -0.51 mA cm-2in 0.5 M H2SO4at -0.8 V vs. Ag/AgCl. The linear sweep voltammetry shows that MoS2in 0.5 M H2SO4has about 55% higher photocurrent density than MoS2in Na2SO4due to the higher protons (H+) in the H2SO4electrolyte solution, which are sufficiently charged to reduce to H2and, therefore hydrogen evolves more rapidly where the photocurrent density and hydrogen generation can be enhanced. MoS2/graphene/SiO2/Si (MGS) has -0.07 mA cm-2at -0.8 V vs. Ag/AgCl of photocurrent density, which is 70% lower than that of bare MoS2because MGS is thicker compared with MoS2. Thus, MoS2has potential as a photocatalyst in photoelectrochemical water splitting. The structure and the morphology of MoS2play an important role in determining the photocurrent performance.

Vertical MoS2 on SiO2/Si and graphene: effect of surface morphology on photoelectrochemical properties.

Two-dimensional materials have attracted intensive attention recently due to their unique optical and electronic properties and their promising applications in water splitting and solar cells. As a representative layer-structured of transition metal dichalcogenides, MoS2 has attracted considerable devotion owing to its exceptional photo and electro properties. Here, we show that the chemical vapour deposition (CVD) growth of MoS2 on Si photocathode and graphene/Si photocathode can be used to prepare photoelectrocatalysts for water splitting. We explore a bottom-up method to grow vertical heterostructures of MoS2 and graphene by using the two-step CVD. Graphene is first grown through ambient-pressure CVD on a Cu substrate and then transferred onto SiO2/Si substrate by using the chemical wet transfer followed by the second CVD method to grow MoS2 over the graphene/SiO2/Si. The effect of the growth temperatures of MoS2 is studied, and the optimum temperature is 800 °C. The MoS2 produced at 800 °C has the highest photocurrent density at -0.23 mA cm-2 in 0.5 M Na2SO4 and -0.51 mA cm-2 in 0.5 M H2SO4 at -0.8 V versus Ag/AgCl. The linear sweep voltammetry shows that MoS2 in 0.5 M H2SO4 has about 55% higher photocurrent density than MoS2 in Na2SO4 due to the higher concentration of protons (H+) in the H2SO4 electrolyte solution. Protons are reduced to H2 at lower overvoltage and hydrogen generation is thus enhanced at higher photocurrent density. MoS2/graphene/SiO2/Si (MGS) has -0.07 mA cm-2 at -0.8 V versus Ag/AgCl of photocurrent density, which is 70% lower than that of bare MoS2 because MGS is thicker compared with MoS2. Thus, MoS2 has potential as a photocatalyst in photoelectrochemical water splitting. The structure and the morphology of MoS2 play an important role in determining the photocurrent performance.