ABSTRACT
Biowaste-derived carbon materials are a sustainable, environmentally friendly, and cost-effective way to create valuable materials. Activated carbon can be a supporting material for electrocatalysts because of its large specific surface area and porosity. However, activated carbon has low catalytic activity and needs to be functionalized with heteroatoms, metals, and combinations to improve conductivity and catalytic activity. Ruthenium (Ru) catalysts have great potential to replace bench market catalysts in hydrogen evolution reaction (HER) applications due to their similar hydrogen bond strength and relatively lower price. This study reports on the synthesis and characterizations of carbon-supported Ru catalysts with large surface areas (~ 1171 m2 g-1) derived from coffee waste. The uniformly dispersed Ru nanoparticles on the porous carbon has excellent electrocatalytic activity and outperformed the commercial catalyst platinum on carbon (Pt/C) toward the HER. As-synthesized catalyst needed only 27 mV to reach a current density of 10 mA cm-2, 58.4 mV dec-1 Tafel slope, and excellent long-term stability. Considering these results, the Ru nanoparticles on coffee waste-derived porous carbon can be utilized as excellent material that can replace platinum-based catalysts for the HER and contribute to the development of eco-friendly and low-cost electrocatalyst materials.
ABSTRACT
The fabrication of freestanding bendable films without polymer substrates is demonstrated as a capacitive humidity-sensing material. The bendable and porous SiO2/Si films are simply prepared by electrochemical-assisted stripping, metal-assisted chemical etching, followed by oxidation procedures. The capacitive humidity-sensing properties of the fabricated porous SiO2/Si film are characterized as a function of the relative humidity and frequency. The remarkable sensing performance is demonstrated in the wide RH range from 13.8 to 79.0%. The sensing behavior of the porous SiO2/Si film is studied by electrochemical impedance spectroscopy analysis. Additionally, the reliability of the porous SiO2/Si sensing material is confirmed by cyclic and long-term sensing tests.
ABSTRACT
Intermetallic copper telluride thin films, which are important in a number of electronics fields, were electrodeposited using a potentiostatic method in low-pH aqueous electrolyte baths with various ion-source concentrations, and the electrical properties of the formed films were investigated after exfoliation from the substrate. The films were electrochemically analyzed by cyclic voltammetry, while surface and cross-sectional morphologies, compositional ratios, and electrical properties were analyzed by scanning electron microscopy, X-ray diffractometry, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and Hall-effect experiments. The copper telluride thin films, which were synthesized at various potentials in each bath, exhibit different composition ratios and structures; consequently, they show a variety of electrical and thermoelectric properties, including different electrical conductivities, carrier concentrations, mobilities, and Seebeck coefficients. Among them, the thin film with a 1:1 Cu:Te ratio delivered the highest power factor due to carrier filtering at the interface between the two phases.
