Positive Role of Synthesis Method and Hard Template on the Catalytic Performance of SAPO-34 in Methanol to Olefin Reaction.

In the present study, SAPO-34 particles were synthesized using hydrothermal (HT) and dry gel (DG) conversion methods in the presence of diethyl amine (DEA) as an organic structure directing agent (SDA). Carbon nanotubes (CNT) were used as a hard template in the synthesis procedure to introduce transport pores into the structures of the synthesized samples. The synthesized samples were characterized with different methods to reveal the effects of synthesis method and using hard template on their structure and catalytic performance in methanol to olefin reaction (MTO). DG conversion method results in smaller particle size in comparison with hydrothermal method, resulting in enhancing catalytic performance. On the other side, using CNT in the synthesis procedure with DG method results in more reduction in particle size and formation of hierarchical structure, which drastically improves catalytic performance.

Nanoengineered Advanced Materials for Enabling Hydrogen Economy: Functionalized Graphene-Incorporated Cupric Oxide Catalyst for Efficient Solar Hydrogen Production.

Cupric oxide (CuO) is a promising candidate as a photocathode for visible-light-driven photo-electrochemical (PEC) water splitting. However, the stability of the CuO photocathode against photo-corrosion is crucial for developing CuO-based PEC cells. This study demonstrates a stable and efficient photocathode through the introduction of graphene into CuO film (CuO:G). The CuO:G composite electrodes are prepared using graphene-incorporated CuO sol-gel solution via spin-coating techniques. The graphene is modified with two different types of functional groups, such as amine (-NH2) and carboxylic acid (-COOH). The -COOH-functionalized graphene incorporation into CuO photocathode exhibits better stability and also improves the photocurrent generation compare to control CuO electrode. In addition, -COOH-functionalized graphene reduces the conversion of CuO phase into cuprous oxide (Cu2O) during photo-electrochemical reaction due to effective charge transfer and leads to a more stable photocathode. The reduction of CuO to Cu2O phase is significantly lesser in CuO:G-COOH as compared to CuO and CuO:G-NH2 photocathodes. The photocatalytic degradation of methylene blue (MB) by CuO, CuO:G-NH2 and CuO:G-COOH is also investigated. By integrating CuO:G-COOH photocathode with a sol-gel-deposited TiO2 protecting layer and Au-Pd nanostructure, stable and efficient photocathode are developed for solar hydrogen generation.

Visible Light Driven Heterojunction Photocatalyst of CuO-Cu2O Thin Films for Photocatalytic Degradation of Organic Pollutants.

A high recombination rate and low charge collection are the main limiting factors of copper oxides (cupric and cuprous oxide) for the photocatalytic degradation of organic pollutants. In this paper, a high performance copper oxide photocatalyst was developed by integrating cupric oxide (CuO) and cuprous oxide (Cu2O) thin films, which showed superior performance for the photocatalytic degradation of methylene blue (MB) compared to the control CuO and Cu2O photocatalyst. Our results show that a heterojunction photocatalyst of CuO-Cu2O thin films could significantly increase the charge collection, reduce the recombination rate, and improve the photocatalytic activity.

Evaluation of Solar-Driven Photocatalytic Activity of Thermal Treated TiO2 under Various Atmospheres.

In this report, the photocatalytic activity of P25 has been explored and the influence of thermal treatment under various atmospheres (air, vacuum and hydrogen) were discussed. The samples' characteristics were disclosed by means of various instruments including X-ray diffraction (XRD), Electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS) and UV⁻vis. This study also accentuates various states of the oxygen vacancy density formed inside the samples as well as the colour turning observed in treated P25 under various atmospheres. Produced coloured TiO2 samples were then exploited for their photocatalytic capability concerning photodegradation of methylene blue (MB) using air mass (AM) 1.5 G solar light irradiation. Our findings revealed that exceptional photocatalytic activity of P25 is related to the thermal treatment. Neither oxygen vacancy formation nor photocatalytic activity enhancement was observed in the air-treated sample. H2-treated samples have shown better photoactivity which even could be further improved by optimizing treatment conditions to achieve the advantages of the positive role of oxygen vacancy (O-vacancy at higher concentration than optimum acts as electron trapping sites). The chemical structure and stability of the samples were also studied. There was no sign of deteriorating of O2-vacancies inside the samples after 6 months. High stability of thermal treated samples in terms of both long and short-term time intervals is another significant feature of the produced photocatalyst.

Preparation of a New Type of Black TiO2 under a Vacuum Atmosphere for Sunlight Photocatalysis.

Black TiO2 as a solar-driven photocatalyst has attracted enormous attention from scientists and engineers in water and wastewater treatment field. Most of the methods used for the preparation of black TiO2 are thermal treatment under a hydrogen atmosphere. Nevertheless, it is well known that working with hydrogen is not safe and needs special maintenance. Here, for the first time, we prepared black TiO2 by sintering P25 pellets at different temperatures (500-800 °C) under a vacuum atmosphere that showed the same performance with the prepared black TiO2 under a hydrogen atmosphere. The samples were characterized by X-ray diffraction, Raman spectra field emission scanning electron microscopy, transmission electron microscopy, electron paramagnetic resonance, X-ray photoelectron spectroscopy, and ultraviolet-visible deep resistivity sounding techniques. The differences between the formation of oxygen vacancy density and color turning in sintered powder and pellet were also studied. The results showed that the color of the P25 powder became darker after sintering but not completely turning to black, whereas the P25 pellets completely turned black after sintering. The resultant black TiO2 was used for the photocatalytic degradation of the acetaminophen (ACE) in aqueous solution under AM 1.5G solar light illumination; it was found that the P25 pellet sintered in 500 °C had the highest photocatalytic performance for ACE degradation under AM 1.5G solar light illumination. The photocatalytic activity of prepared black TiO2 under vacuum and hydrogen atmospheres was also compared together; the results showed that photocatalytic activities of both samples were so close together. The existence of the oxygen vacancy after 6 months and long and short-term stability (by application for photocatalytic degradation of ACE in an aqueous solution) of the black TiO2 pellets was also studied; the results showed that the TiO2 pellets in aqueous phase had acceptable stability.