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Hydrogen production from humidity in the ambient air reduces the maintenance costs for sustainable solar-driven water splitting. We report a gas-diffusion porous photoelectrode consisting of tungsten trioxide (WO3) nanoparticles coated with a proton-conducting polymer electrolyte thin film for visible-light-driven photoelectrochemical water vapor splitting. The gas–electrolyte–solid triple phase boundary enhanced not only the incident photon-to-current conversion efficiency (IPCE) of the WO3 photoanode but also the Faraday efficiency (FE) of oxygen evolution in the gas-phase water oxidation process. The IPCE was 7.5% at an applied voltage of 1.2 V under 453 nm blue light irradiation. The FE of hydrogen evolution in the proton exchange membrane photoelectrochemical cell was close to 100%, and the produced hydrogen was separated from the photoanode reaction by the membrane. A comparison of the gas-phase photoelectrochemical reaction with that in liquid-phase aqueous media confirmed the importance of the triple phase boundary for realizing water vapor splitting.

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The use of injectable materials as a biofiller for soft tissue augmentation has been increasing worldwide. Levan is a biocompatible and inexpensive polysaccharide with great potential in biomaterial applications, but it has not been extensively studied. In this study, we evaluated the potential of levan as a new material for dermal fillers and prepared an injectable and physical levan-based hydrogel by combining levan with Pluronic and carboxymethyl cellulose (CMC). A sol state was prepared by mixing the polymers in a specific ratio at 4 °C for 2 days and the hydrogel was formed by increasing the temperature to 37 °C. The elastic modulus of the levan hydrogel was higher than that of a hyaluronic acid (HA)-based hydrogel. The SEM images of the levan hydrogel showed an interconnected porous structure, similar to the HA hydrogel. Levan showed non-cytotoxicity, enhanced cell proliferation, and higher amount of collagen synthesis in human dermal fibroblast cells compared to HA. The injected levan hydrogel was biocompatible and stable over 2 weeks in vivo, longer than the Pluronic F127 hydrogel or HA hydrogel. Also, the levan hydrogel showed a higher amount of collagen production than the HA hydrogel in vivo. More importantly, the levan hydrogel showed enhanced anti-wrinkle efficacy compared to the HA hydrogel in a wrinkle model mouse. Thus, the levan hydrogel with injectability, biocompatibility, and an anti-wrinkle effect has high potential as an alternative to existing commercial dermal fillers.

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The layer of electrocatalytic mixed oxides is known as a dimensionally stable anode (DSA) used in many industrial electrochemical processes. A layer of iridium oxide (IrO2) and tantalum oxide (Ta2O5) coated on a titanium (Ti) substrate electrode is active for oxygen evolution reaction (OER) in acidic solution. Herein, we used a porous Ti felt composed of microfibers as a conductive substrate for the IrO2-Ta2O5 electrocatalytic layer. The effect of the Ti substrates and the calcination temperature on the electrocatalytic activity for OER was investigated by cyclic voltammetry in an acidic sulfate solution. The results show that the IrO2-Ta2O5 layer on the porous Ti felt with a large surface area was more active than the layer on the conventional Ti plate. The electrocatalytic activity of IrO2-Ta2O5 layers was maximized by calcination at 350 °C and decreased by increasing the calcination temperature with the decrease of the double-layer capacitance (C dl), which is recognized as an electrochemically active surface area (ECSA). The IrO2-Ta2O5 thin layer on the Ti felt was amorphous in the measurement of X-ray diffraction and Raman spectroscopy. The amorphous layer was confirmed to have rare cracks, larger ECSA, and higher catalytic activity for OER. The overpotential required to reach the current density of 10 mA cm–2 was only 0.27 V. The constant current was the Faradaic current for water oxidation to evolve O2.

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