Zhu Luo

Facile Synthesis of Co3O4@CNT with High Catalytic Activity for CO Oxidation under Moisture-Rich Conditions

The catalytic oxidation reaction of CO has recently attracted much attention because of its potential applications in the treatment of air pollutants. The development of inexpensive transition metal oxide catalysts that exhibit high catalytic activities for CO oxidation is in high demand. However, these metal oxide catalysts are susceptible to moisture, as they can be quickly deactivated in the presence of trace amounts of moisture. This article reports a facile synthesis of highly active Co3O4@CNT catalysts for CO oxidation under moisture-rich conditions. Our synthetic routes are based on the in situ growth of ultrafine Co3O4 nanoparticles (NPs) (∼2.5 nm) on pristine multiwalled CNTs in the presence of polymer surfactant. Using a 1% CO and 2% O2 balanced in N2 (normal) feed gas (3-10 ppm moisture), a 100% CO conversion with Co3O4@CNT catalysts was achieved at various temperatures ranging from 25 to 200 °C at a low O2 concentration. The modulation of surface hydrophobicity of CNT substrates, other than direct surface modification on the Co3O4 catalytic centers, is an efficient method to enhance the moisture resistance of metal oxide catalysts for CO oxidation. After introducing fluorinated alkyl chains on CNT surfaces, the superhydrophobic Co3O4@CNT exhibited outstanding activity and durability at 150 °C in the presence of moisture-saturated feed gas. These materials may ultimately present new opportunities to improve the moisture resistance of metal oxide catalysts for CO oxidation.

The viability of photocatalysis for air purification.

Photocatalytic oxidation (PCO) air purification technology is reviewed based on the decades of research conducted by the United Technologies Research Center (UTRC) and their external colleagues. UTRC conducted basic research on the reaction rates of various volatile organic compounds (VOCs). The knowledge gained allowed validation of 1D and 3D prototype reactor models that guided further purifier development. Colleagues worldwide validated purifier prototypes in simulated realistic indoor environments. Prototype products were deployed in office environments both in the United States and France. As a result of these validation studies, it was discovered that both catalyst lifetime and byproduct formation are barriers to implementing this technology. Research is ongoing at the University of Connecticut that is applicable to extending catalyst lifetime, increasing catalyst efficiency and extending activation wavelength from the ultraviolet to the visible wavelengths. It is critical that catalyst lifetime is extended to realize cost effective implementation of PCO air purification.

Ligand‐Assisted Co‐Assembly Approach toward Mesoporous Hybrid Catalysts of Transition‐Metal Oxides and Noble Metals: Photochemical Water Splitting

A bottom-up synthetic approach was developed for the preparation of mesoporous transition-metal-oxide/noble-metal hybrid catalysts through ligand-assisted co-assembly of amphiphilic block-copolymer micelles and polymer-tethered noble-metal nanoparticles (NPs). The synthetic approach offers a general and straightforward method to precisely tune the sizes and loadings of noble-metal NPs in metal oxides. This system thus provides a solid platform to clearly understand the role of noble-metal NPs in photochemical water splitting. The presence of trace amounts of metal NPs (≈0.1 wt %) can enhance the photocatalytic activity for water splitting up to a factor of four. The findings can conceivably be applied to other semiconductors/noble-metal catalysts, which may stand out as a new methodology to build highly efficient solar energy conversion systems.

Potassium modified layered Ln2O2CO3 (Ln: La, Nd, Sm, Eu) materials: efficient and stable heterogeneous catalysts for biofuel production.

Potassium modified layered Ln2O2CO3 (Ln: La, Nd, Sm, Eu) biodiesel catalysts were prepared by a coprecipitation method followed by an overnight reflux. A high fatty acid methyl ester (FAME) yield (>95%) was achieved under mild reaction conditions (<100 °C). The FAME yields were investigated as a function of temperature and catalyst weight percentage. Nd2O2CO3 shows a better catalytic performance with a higher reaction rate than the industrial homogeneous KOH catalyst using both microwave irradiation and conventional heating methods. Approximately 100% FAME yield can be reached at 95 °C (microwave radiation) by 1.0 wt% Nd2O2CO3 within 10 min, while the same yield can be reached by 3.0 wt% Nd2O2CO3 at 95 °C (conventional heating method). In addition, leaching tests of the catalysts were performed; no leached rare earth metal ions were detected and the amounts of leached potassium were all under 5 ppm (ASTM standard). The synthesized layered Ln2O2CO3 materials offer a group of ideal alternative catalysts for industrial biodiesel production.

High-rate and long-life of Li-ion batteries using reduced graphene oxide/Co3O4 as anode materials

Metal oxides as Li-ion battery anodes have received a great deal of attention because they offer a higher specific capacity than state-of-the-art commercial graphite. However, a large volume change and severe particle aggregation during battery operation have greatly impeded their practical application. Herein, we report a facile one-step microwave-assisted route for growing Co3O4 nanoparticles on reduced graphene oxide that results in a high performance anode material for Li-ion batteries. The lithium battery performances of several systems with varied reduced graphene oxide contents were studied. The optimized composites exhibit a high surface area of 222 m2 g−1, and a wide pore size distribution of 1.4 to 300 nm. More importantly, the Li-ion battery shows a high capacity of ∼1300 mA h g−1 at a high rate of 1C (1C = 890 mA g−1), long life of over 600 cycles, good capacity retention, and excellent rate capability. The synthesis process is simple, energy efficient, and time-saving, providing a new path in designing high-performance electrodes for Li-ion batteries.

Single-step One-pot Synthesis of TiO2 Nanosheets Doped with Sulfur on Reduced Graphene Oxide with Enhanced Photocatalytic Activity

A hybrid photocatalyst based on anatase TiO2 was designed by doping TiO2 with sulfur and incorporating reduced graphene oxide (TiO2-S/rGO hybrid), with an aim to narrow the band gap to potentially make use of visible light and decrease the recombination of excitons, respectively. This TiO2-S/rGO hybrid was successfully synthesized using a one-pot hydrothermal method via single-step reaction. The structure and morphology of the TiO2-S/rGO hybrid catalyst was carefully characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Its photocatalytic reactivity was evaluated by the degradation of methyl blue. The results showed that both the doping of sulfur and the introduction of rGO worked as designed, and the TiO2-S/rGO hybrid exhibited high photocatalytic activity under simulated sunlight. Considering both the facile and scalable reaction to synthesize TiO2-S/rGO hybrid, and its excellent photocatalytic performance, such TiO2-S/rGO hybrids are expect to find practical applications in environmental and energy sectors.