Dong-Hau Kuo

A simple one-pot synthesis of a Zn(O,S)/Ga2O3 nanocomposite photocatalyst for hydrogen production and 4-nitrophenol reduction

Noble metal-free Zn(O,S)/Ga2O3 nanocomposite photocatalysts containing different amounts of Ga2O3 have been synthesized using a precipitation method at 90 °C. The as-prepared catalysts were characterized and their composite nature was confirmed. The Zn(O,S)/Ga2O3 catalysts were examined for their ability to evolve hydrogen under low UV light illumination (0.088 mW cm−2) and to provide hydrogen for 4-nitrophenol (4-NP) reduction. Gas chromatography measurements revealed that hydrogen was produced at a rate of 280 μmol g−1 h−1 W−1, while UV-vis absorption and high-performance liquid chromatography (HPLC) measurements confirmed the formation of 4-aminophenol (4-AP) as a product of 4-NP reduction. The heterojunction formation between the Zn(O,S) and Ga2O3 phases enhanced the photocatalytic activity, compared to the single Zn(O,S) and Ga2O3 phases. Surface oxygen anions and oxygen vacancies played important roles in the photocatalytic mechanism to evolve hydrogen and to utilize hydrogen ions in 4-NP reduction. The photocatalytic hydrogen evolution reaction and its utilization for 4-NP reduction to 4-AP were evaluated and elucidated in this work.

Abiotic Synthesis with the C-C Bond Formation in Ethanol from CO 2 over (Cu, M )(O,S) Catalysts with M = Ni, Sn, and Co

We demonstrate copper-based (Cu,M)(O,S) oxysulfide catalysts with M = Ni, Sn, and Co for the abiotic chemical synthesis of ethanol (EtOH) with the C-C bond formation by passing carbon dioxide (CO2) through an aqueous dispersion bath at ambient environment. (Cu,Ni)(O,S) with 12.1% anion vacancies had the best EtOH yield, followed by (Cu,Sn)(O,S) and (Cu,Co)(O,S). The ethanol yield with 0.2 g (Cu,Ni)(O,S) catalyst over a span of 20 h achieved 5.2 mg. The ethanol yield is inversely proportional to the amount of anion vacancy. The kinetic mechanism for converting the dissolved CO2 into the C2 oxygenate is proposed. Molecular interaction, pinning, and bond weakening with anion vacancy of highly strained catalyst, the electron hopping at Cu+/Cu2+ sites, and the reaction orientation of hydrocarbon intermediates are the three critical issues in order to make the ambient chemical conversion of inorganic CO2 to organic EtOH with the C-C bond formation in water realized. On the other hand, Cu(O,S) with the highest amount of 22.7% anion vacancies did not produce ethanol due to its strain energy relaxation opposing to the pinning and weakening of O-H and C-O bonds.

Enhancing the photodegradation of charged pollutants under visible light in Ag2O/g-C3N4 catalyst by Coulombic interaction

Ag2O/g-C3N4 catalyst with a p–n junction to form nanodiode decorated on g-C3N4 was successfully prepared with a facile method. The Ag2O/g-C3N4 photoactivity was investigated through degradation of methylene blue (MB), methyl orange (MO), rhodamine B (RhB), and phenol. XRD, XPS, FTIR, FE-SEM, HR-TEM, UV–Vis DRS, PL, and BET of different analytical techniques were used for the Ag2O/g-C3N4 characterizations. The results showed that 5% Ag2O/g-C3N4 exhibited excellent catalytic activity for the degradation of positively charged dye of MB and negatively charged dye of MO under visible light irradiation, but not good for uncharged pollutant of RhB. Ag2O/g-C3N4 also exhibited relatively good stability and durability during the repeated dye removal experiments. To explain the different photoactivities, the Coulombic interaction mechanism between dyes and catalyst was proposed.