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Bismuth vanadate, BiVO4, is a visible-light response semiconductor for photocatalysis applications such as organic pollutants degradation, oxygen production and carbon dioxide reduction. However, as a single-phase photocatalyst, BiVO4 efficiency is limited by the unpreferable recombination of the photoexcited electron (e−) and hole (h+). Thus, strategies have been designed to enhance the photocatalytic efficiency by promoting the separation of electrons and holes. This can be done by controling the morphology and crystallographic facets of BiVO4, and by building p–n junction photocatalytic systems with a combination of n-type semiconductors (BiVO4) and p-type semiconductors or a monoclinic–tetragonal heterostructure of BiVO4. In particular, a direct p–n junction photocatalytic system with tetragonal zircon-structured BiVO4 (t-z) and monoclinic scheelite-structured BiVO4 (m-s) combination has recently attracted attention. Here we review the synthesis of the monoclinic–tetragonal heterostructured BiVO4 photocatalyst (m–t BiVO4) by calcination, hydrothermal, microwave-assisted hydrothermal and solvothermal methods. m–t BiVO4 formation and the transmission phase between t-z and m-s are controlled by the calcining temperature, precursor pH, metal doping content, type of solvent, implementation of precursors and reaction conditions. We discuss m–t BiVO4 crystal structure, optical characteristics and photocatalytic principles. Successful formation of BiVO4 crystals with a m-s/t-z heterostructure is based on data from X-ray diffraction (XRD), Raman and ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS). In the m–t BiVO4 heterostructure, a direct p–n junction photocatalytic system is established. When this system is exposed to visible light, the electrons in the conduction band of m-s BiVO4, a n-type semiconductor, migrate easily to the conduction band of t-z BiVO4, while the holes on valence band of t-z BiVO4, a p-type semiconductor, move to the valence band of m-s BiVO4 through an internal electric field. As a result, the e−/h+ charge carriers are spatially separated.

The efficient reduction of CO2 into valuable products such as methanol, over metal-organic frameworks (MOFs) based catalyst, has received much attention. The photocatalytic reduction is considered the most economical method due to the utilization of solar energy. In this study, Copper (II)/Zeolitic Imidazolate Framework-8 (Cu/ZIF-8) catalysts were synthesized via a hydrothermal method for photocatalytic reduction of CO2 to methanol. The synthesized catalysts were characterized by X-ray Photoelectron Spectroscopy (XPS), Field Emission Scanning Electron Microscopy (FESEM) coupled with Energy Dispersive X-ray (EDX), Ultraviolet-visible (UV-vis) spectroscopy, and X-Ray Diffraction (XRD). The host ZIF-8, treated with 2 mmol copper prepared in 2M ammonium hydroxide solution showed the highest photocatalytic activity. The crystal structures of ZIF-8 and 2Cu/ZIF-8N2 catalysts were observed as cubic and orthorhombic, respectively and the XPS analysis confirmed the deposition of Cu (II) ions over ZIF-8 surface among all the prepared catalysts. The orthorhombic structure, nano-sized crystals, morphology and Cu loading of the 2Cu/ZIF-8N2 catalyst were the core factors to influence the photocatalytic activity. The yield of Methanol was found to be 35.82 µmol/L·g after 6 h of irradiations on 2Cu/ZIF-8N2 catalyst in the wavelength range between 530–580 nm. The copper-based ZIF-8 catalyst has proven as an alternative approach for the economical photocatalytic reduction of CO2 to CH3OH.

High production of biodiesel results in a surplus of glycerol as a byproduct that leads to a drastic decline in the glycerol price as well as overall biodiesel production. Alternative methods must be introduced for the economical process for biodiesel production via utilization of crude glycerol into valuable chemicals or fuel additives. This study introduces an ecofriendly process of solketal synthesis from glycerol and acetone in the presence of a novel metakaolin clay catalyst, which is a useful additive in biodiesel or gasoline, in order to enhance the octane number and to control the emissions. Moreover, kaolin clay catalysts are low cost, abundantly available, eco-friendly and one of the more promising applications for solketal synthesis. In this study, raw kaolin clay was activated with an easy acid activation technique, modification in physicochemical and textural properties were determined by using X-ray diffraction (XRD), Fourier Transform Infra-Red (FTIR) spectroscopy, Brunauer–Emmett–Teller (BET) and Field Emission Scanning Electron Microscope. Among all acid-treated catalysts, metakaolin K3 have shown best catalytic properties, high surface area and pore size after acid activation with 3.0 mol/dm3 at 98 °C for 3 h. Acetalization of glycerol with acetone carried out in the presence of an environmentally friendly and inexpensive novel metakaolin K3 catalyst. The maximum yield of solketal obtained was 84% at a temperature of 50 °C, acetone/glycerol molar ratio 6/1 and for 90 min with novel metakaolin clay catalyst. Effect of various parameters (time, temperature, acetone/glycerol molar ratio, catalyst loading) on the solketal yield and glycerol conversion was discussed in detail. This approach offers an effective way to transform glycerol into solketal—a desirable green chemical with future industrial applications.

Metal-organic frameworks (MOFs), which are self-assembled and can be synthesized by the coordination of metal cation/clusters with organics linkers. Copper/zeolitic imidazolate framework-8 (Cu/ZIF-8) MOF catalyst was successfully synthesized by reaction of metal sulfates of Cu with ZIF-8 via hydrothermal method. Thermogravimetric analysis (TGA) exhibits the excellent thermal stability up to 450°C of the Cu/ZIF-8 catalyst. Fourier transform infrared spectroscopy (FTIR) confirmed the ZIF-8 structure and the addition of copper metal. Field emission scanning electron microscopy (FESEM) images exhibit great morphologies which confirms the synthesis of Cu/ZIF-8 catalyst. UV-Vis (Ultraviolet-visible) spectroscopy and DRS (diffuse reflectance spectroscopy) show more absorbance in the visible region of Cu/ZIF-8 and lower band gap energy respectively, which leads to photocatalytic support. Our discoveries investigated a basic and intense approach to photocatalyst without losing their properties.

This study involves the development of novel mesoporous Zr-MCM-48 photocatalyst impregnated with Cu-porphyrin (CuTPP) having Si/Zr ratio of 100, 50 and 25. The synthesized materials were applied as hybrid photocatalyst affording mid-gap energy states and Zi 3+ sites for reduction of CO 2 into methanol selectively using UV–Visible light treatment. Interestingly, Zr-MCM-48 displayed significant photocatalytic reduction ability under UV–Vis wavelength. The bare Zr-based MCM-48(25) matrix with maximum Zr content in catalyst enhanced the photocatalytic activity with 47.5 µmol methanol formation, possessing high surface area S BET of 1324 m 2  g −1 , under UV–Visible light irradiation. The characterization results highlighted the influence of visible light active Cu-porphyrin interaction over Zr-MCM-48 silica frameworks due to transition of electrons from the porphyrin centres to the active Zr sites as evident from DRS analysis. Moreover, the impregnation of Cu-porphyrin over Zr-MCM-48(25) displayed methanol formation about 365.11 µmol under UV–Visible light using 0.1 M NaOH and 0.1 M Na 2 SO 3 . Also, the effect of varying reaction conditions shown that catalyst concentration, metal loading, light intensity and stirring speed pronouncedly impact the formation of methanol.

The design of economical and robust catalysts is a substantial challenge for the dry reforming of methane (DRM). Monometallic nickel-based catalysts used for DRM reactions had comparable activity to noble metals. However, they turned out to be less stable during the reactions. As a continuation of the interest in synthesizing catalysts for DRM, this paper evaluates the catalytic performance of bimetallic Co–Ni catalysts regarding their synergy effect, with graphene oxide (GO) as support for the first time. The synthesized bimetallic catalysts prepared via the wet-impregnation method were characterized using N2 physisorption analysis, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and X-ray diffraction (XRD). The catalytic test was performed in a stainless-steel tubular reactor in atmospheric conditions with a reaction temperature of 800 °C, time-on-stream (TOS) of 300 min and CH4: CO2 being fed with a ratio of 1:1. The bimetallic 10 wt%Co–10 wt%Ni/GO and 20 wt%Co–10 wt%Ni/GO catalysts had a similar BET specific surface area in N2 physisorption analysis. The XRD pattern displayed a homogeneous distribution of the Co and Ni on the GO support, which was further validated through SEM–EDX. The conversion of CO2, CH4, and H2 yield decreased with reaction time due to the massive occurrence of side reactions. High conversions for CO2 and CH4 were 94.26% and 95.24%, respectively, attained by the bimetallic 20 wt%Co–10 wt%Ni/GO catalyst after 300 min TOS, meaning it displayed the best performance in terms of activity among all the tested catalysts.

In order to identify the best possible reaction media for performing H 2 S conversion, a total number of 300 different ILs from a combination of 20 cations and 15 anions were screened via COSMO-RS model simulations. By COSMO-RS method, thermodynamic and physicochemical properties of 300 ILs such as Henry’s law constants, activity coefficient, selectivity, capacity and performance index are obtained and analyzed. Thus, by comparing the performance of ILs via COSMO-RS, a series of TSILs containing cation of [P 66614 ] with metal chloride anions such as Fe, Ga and Sn were chosen and selected for synthesis based on their performance predicted by COSMO-RS and their economic values. Consequently, the physiochemical properties such as density, viscosity, thermal properties, as well as H2S absorptive oxidation performances in those TSILs will be systematically investigated.

The abundance of carbon dioxide gas in the atmosphere raises concerns as it affects the environmental sustainability, human's wellbeing as well as the nature. The photocatalysis conversion of carbon dioxide produces valuable gas and limits environmental issue in the same time. Therefore, it attracts the attention to synthesize photocatalyst that is active under visible light irradiation since sunlight provides abundant photon energy mostly in visible light range. In this study, CdS as visible light-active photocatalyst is loaded with nickel to improve its performance to convert CO2 to methanol under irradiation of 500 W of Xe lamp as visible light source. The spherical nanoparticles morphology can be observed for synthesized CdS and Ni/CdS by using field emission scanning electron microscopy (FE-SEM) analysis. The yield of methanol was examined by using high performance liquid chromatography (HPLC). The result shows that the yield can be improved from 11 μmol/g-catalyst to 2348 μmol/g-catalyst by loading of 3wt% of nickel in CdS. The further loading of nickel decreased the yield of methanol.

This study was conducted for microwave assisted synthesis of stable gold nanoparticles (AuNPs) by reduction of chloroauric acid with Elaeis Guineensis (palm oil) kernel (POK) extract which was prepared in aqueous solution of ionic liquid, [EMIM][OAc], 1-Ethyl-3-methylimidazolium acetate. Effect of initial pH of reaction mixture (3.5 - 8.5) was observed on SPR absorbance, maximum wavelength (λmax) and size distribution of AuNPs. Change of pH of reaction mixture from acidic to basic region resulted in appearance of strong SPR absorption peaks and blue shifting of λmax from 533 nm to 522 nm. TEM analysis revealed the formation of predominantly spherical AuNPs with mean diameter of 8.51 nm. Presence of reducing moieties such as flavonoids, phenolic and carboxylic groups in POK extract was confirmed by FTIR analysis. Colloidal solution of AuNPs was remained stable at room temperature and insignificant difference in zeta value was recorded within experimental tenure of 4 months.

Non-oxidative decomposition of natural gas is a handsome technique for clean hydrogen production but high reaction temperature and rapid catalyst deactivation limitizes its applications. In current work, decomposition of methane into COX free hydrogen and carbon nanofiber were studied over the bimetallic catalysts. The materials were prepared by wet impregnation method and analyzed by BET, TGA, XRD, FESEM, and TEM. It was observed that with an increase in the metal loading, the surface area was reduced but the methane conversions and catalyst stability were improved since the catalyst activity depend upon the active nickel sites that compensate the surface deficiencies. The highest conversion was given by Ni-Cu-Pd/Al2O3 (80%) over a period of 6 h despite having a low BET surface area (2.43 m2 g−1). The physiochemical properties reported that the synthesized catalyst possessed nanostructure and CNF were also produced along with hydrogen as products of TCD.