Dong Jin Ham

Synthesis of hexagonal WO3 nanowires by microwave-assisted hydrothermal method and their electrocatalytic activities for hydrogen evolution reaction

Hexagonal WO3 (hex-WO3) nanowires with high aspect ratio and crystallinity have been prepared for the first time by a microwave-assisted hydrothermal method. By using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and high resolution transmission electron microscopy, the phase and morphology of the products were identified, which were controlled by reaction temperature, holding time and added salts. Uniform hex-WO3 nanowires with a diameter of 5–10 nm and lengths of up to several micrometres were synthesized by a microwave-assisted hydrothermal process at 150 °C for 3 h in a solution containing (NH4)2SO4 as a capping reagent and Na2WO4 as a starting material. The aspect ratio and specific surface area of hex-WO3 nanowires were 625 and 139 m2 g−1, respectively, which represented one of the highest values reported for WO3. The electrocatalytic activity for hydrogen evolution reaction of hex-WO3 nanowires was also investigated by cyclic voltammetry and linear sweep voltammetry. The results demonstrated that hex-WO3 nanowires were a promising electrocatalyst for the hydrogen evolution reaction (HER) from water.

Photosynthesis of formate from CO2 and water at 1% energy efficiency via copper iron oxide catalysis

Solar conversion of carbon dioxide and water to value-added chemicals remains a challenge. A number of solar-active catalysts have been reported, but they still suffer from low selectivity, poor energy efficiency, and instability, and fail to drive simultaneous water oxidation. Herein, we report CuFeO2 and CuO mixed p-type catalysts fabricated via widely employed electroplating of earth-abundant cupric and ferric ions followed by annealing under atmospheric air. The composite electrodes exhibited onset potentials at +0.9 V vs. RHE in CO2-purged bicarbonate solution and converted CO2 to formate with over 90% selectivity under simulated solar light (air mass 1.5, 100 mW cm−2). Wired CuFeO2/CuO photocathode and Pt anode couples produced formate for over 1 week at a solar-to-formate energy conversion efficiency of ∼1% (selectivity >90%) without any external bias while O2 was evolved from water. Isotopes and nuclear magnetic resonance analyses confirmed the simultaneous production of formate and O2 at the stand-alone couples.