Hairus Abdullah

Cu Mn OS Nanoflowers with Different Cu + /Cu 2+ Ratios for the CO 2 -to-CH 3 OH and the CH 3 OH-to-H 2 Redox Reactions

A conservative CO2-Methanol (CH3OH) regeneration cycle, to capture and reutilize the greenhouse gas of CO2 by aqueous hydrogenation for industry-useful CH3OH and to convert aqueous CH3OH solution by dehydrogenation for the clean energy of hydrogen (H2), is demonstrated at normal temperature and pressure (NTP) with two kinds of CuMnOS nanoflower catalysts. The [Cu+]-high CuMnOS led to a CH3OH yield of 21.1 mmol·g−1catal.·h−1 in the CuMnOS-CO2-H2O system and the other [Cu+]-low one had a H2 yield of 7.65 mmol·g−1catal.·h−1 in the CuMnOS-CH3OH-H2O system. The successful redox reactions at NTP rely on active lattice oxygen of CuMnOS catalysts and its charge (hole or electron) transfer ability between Cu+ and Cu2+. The CO2-hydrogenated CH3OH in aqueous solution is not only a fuel but also an ideal liquid hydrogen storage system for transportation application.

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.

Synthesis and characterization of La-doped Zn(O,S) photocatalyst for green chemical detoxification of 4-nitrophenol

La-doped Zn(O,S) nanoparticles (NPs) with different contents of lanthanum have been synthesized with a simple sol-gel method at low temperature (90 ℃) for 4-nitrophenol (4-NP) detoxification. The as-prepared catalysts were characterized with X-ray diffraction (XRD), scanning electron microscope (SEM), high resolution transmission electron microscope (HRTEM), photoluminescence (PL) and UV-vis absorbance spectroscopy, X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), and photoresponsivity. In this work, it is considered that the detoxification of 4-NP to 4-aminophenol (4-AP) without NaBH4 by using photocatalytic method is a green chemical conversion. The experimental data showed 30 ppm toxic 4-NP had been totally converted to useful 4-aminophenol (4-AP) with lower toxicity in 2 h, which was confirmed with a specific peak shift as indicated with UV-vis absorbance spectra and high performance liquid chromatography (HPLC) measurement. The lower amount of evolved hydrogen from photocatalytic process on La-doped Zn(O,S) NPs in the presence of 4-NP confirmed the produced hydrogen was consumed as a reducing agent during the 4-NP-to-4-AP conversion. The photocatalytic detoxification of 4-NP to 4-AP had been demonstrated and an appropriate mechanism based on the experimental data had been proposed and elucidated in this work.

Cobalt-doped Zn(O,S)/Ga2O3 nanoheterojunction composites for enhanced hydrogen production

Cobalt-doped Zn(O,S)/Ga2O3 nanoheterojunction composites with different Co contents were synthesized and characterized. The as-prepared nanocomposite photocatalysts were tested for their capabilities to evolve hydrogen with ethanol as a hole scavenger under low power UV illumination (0.088 mW cm−2 or approximately 1/40 UV intensity of sunlight). The highest hydrogen evolution rate of 5.10 mmol g−1 h−1 was achieved. It was found that the enhanced hydrogen evolution amount was 50% higher than that of pure Zn(O,S) and 14% higher than that of the Co-free Zn(O,S)/Ga2O3 nanocomposite prepared in our previous study. This study revealed that the role of Co was considerably crucial to enhance the efficiency of photocarrier separation and lower the electron transfer resistances on catalyst surfaces, leading to higher photoresponse current and photocatalytic activity. The photocatalytic evaluation of Co-doped Zn(O,S)/Ga2O3 nanocomposites with different Co contents was carried out and an appropriate photoreaction mechanism is proposed to elucidate the enhanced photocatalytic activity in this study.

Convenient synthesis of Mn-doped Zn (O,S) nanoparticle photocatalyst for 4-nitrophenol reduction

The conversion of 4-nitrophenol as a toxic and waste pollutant to 4-aminophenol as a non-toxic and useful compound by photocatalytic reduction is highly important. In this work, the solid-solution concept by doping was involved to synthesis earth-abundant and green material of Mn-doped Zn(O,S). Zn(O,S) with different Mn doping contents was easily synthesized at low temperature 90°C for 4-NP reduction without using the reducing agent of NaBH4. The Mn-doped Zn(O,S) catalyst exhibited the enhancements in optical and electrochemical properties compared to un-doped Zn(O,S).It was found that 10% Mn-doped Zn(O,S) had the best properties and it could totally reduce 4-NP after 2h photoreactions under low UV illumination. The hydrogen ion was proposed to involve the 4-NP reduction to 4-AP, which is hydrogen ion and electron replaced the oxygen in amino (NO2) group of 4-NP to form the nitro (NH2) group. We alsoproposed the incorporation of Mn in Zn site in the Zn(O,S) host lattice could make the oxygen surface bonding weak for easily forming the oxygen vacancy. The more oxygen vacancy for more hydrogen ion would be generated to consume for 4-NP reduction.

Photocatalytic antibacterial activity of copper-based nanoparticles under visible light illumination

Copper oxide and sulfide nanoparticles after annealing treatment at 400 °Chave been characterized and tested for their bactericidal properties toward Staphylococcus aureus and Escherichia coli under the dark and LED light illuminated conditions. It was found that the nanoparticles with the formation of CuS/Cu2S/CuO nanoheterostructuresexhibited a great capability of killing Staphylococcus aureus and Escherichia coli with or without light illumination. The antibacterial activity of the nanoparticles was demonstrated and simply observed with colony counting method. A mechanism of the antibacterial behaviour had been proposed and elucidated in this work.