In order to reduce the impact of production processes on the environment, wastes can be modified by metallic supported catalysts (MSCs). One of the techniques in preparing supports for MSCs could be Plasma Electrolytic Oxidation (PEO) process used to produce a uniform, adhesive and porous layer on the surface of metals, including Ti as the layers which are carriers for catalysts. As a result, more diverse products in terms of shape and mechanical properties, especially in comparison with ceramic based catalysts, could be produced. In this review, application of the PEO process to the production of MSCs will be presented.

Catalytic methane decomposition is believed to be an economic and environmental friendly route for the production of COx free hydrogen and high quality carbon nanotubes. However, the development of active and stable catalysts remains a significantly challenging research topic. This study focuses on the development of highly active and stable silica-supported Fe-based catalysts for the thermal decomposition of methane into hydrogen and high quality carbon nanotubes. A series of Fe/SiO2 catalysts with varying Fe loading in the range between 25 wt% and 100 wt% were synthesized by the solution combustion synthesis (SCS) method. The synthesized catalysts were characterized by various bulk sensitive and surface sensitive analytical tools, such as SEM, XRD, HRTEM, BET and Raman spectroscopy. All supported catalysts exhibited comparatively high activity than the unsupported 100 wt% Fe (denoted as 100F) catalyst which was the least active. Moreover, the catalytic activity in terms of methane conversion, methane decomposition rate, growth activities as well as carbon yields increased with an increase in the Fe loading. At an operating temperature of 650 °C and a GHSV of 8000 h−1, the 75FS catalyst, with a composition of 75 wt%Fe/SiO2, demonstrated the highest methane decomposition rate of 0.75gCH4/g-cat.h among the investigated catalysts. Additionally, after achieving initial stability at about 120 min, this catalyst remained active throughout testing on stream for 900 min. TEM and SEM analysis of the spent catalyst showed that the supported 75FS catalyst produced multi-walled carbon nanotubes with uniform diameters of 28 nm and with Id/Ig ratio of 0.454 whereas the unsupported 100F catalyst mainly produced graphene sheets.

The hybrid water electrolysis affords a green route for the generation of fine chemicals accompanied with hydrogen production relying on the rapid development of anodic electrocatalysts. Herein, a nickel‐cobalt layered double hydroxide (NiCo LDH) modified nickel foam, prepared at room temperature via simple soaking processes, could effectively catalyze the dehydrogenation oxidation of primary amines to generate aromatic and aliphatic nitriles with good yields. Further expanding the application of the easily available electrode, the NiCo LDH electrode could function as the electron reservoir to realize the decoupled water electrolysis with 100% coulombic efficiency in the membrane-free electrolytic cell.

Magnetic-field effect on heterogenous photocatalysis was investigated on Pt/TiO2 by photocatalytic oxidation of 2-propanol. Two-level factorial design of dissolved oxygen concentration (DO), temperature, and magnetic flux density was applied for the first time. The high magnetic flux density with high DO significantly enhanced 22% 2-propanol oxidation. The singlet-triplet intersystem crossing of radicals, as well as the Lorentz force suppressing the recombination of photogenerated electrons and holes, enabled such an extraordinary magnetic effect. Moreover, paramagnetic oxygen and platinum on TiO2 reinforced the intersystem crossing, which contributed to the significant improvement of photocatalytic oxidation of 2-propanol under magnetic field.

Abstract not available

Keggin-type heteropoly acids (HPAs) have strong Brønsted acidity and are widely used as acid catalysts. The aim of this work is the systematic characterisation of the acid strength of HPA catalysts comprising H3PW12O40 and H4SiW12O40 supported on SiO2, TiO2 and ZrO2 with 10–100% HPA loading and testing their activity in dehydration of alcohols to gain new mechanistic insight regarding the role of bulk-type and surface-type HPA catalysis in this reaction. The HPA catalysts were prepared by impregnation from an aqueous solution and characterised using BET, XRD, TGA, DRIFTS and ICP–OES. The acid strength of HPA catalysts was determined by NH3 adsorption microcalorimetry and found to decrease in the order HPA/SiO2 > HPA/TiO2 > HPA/ZrO2. For each type of HPA catalyst, the acid strength increased with increasing HPA loading. This can be attributed to HPA-support interaction reducing the strength of HPA proton sites at low HPA loadings. The activity of HPA catalysts was tested in the gas-phase dehydration of MeOH and i-PrOH in a fixed-bed reactor. Evidence was obtained that alcohol dehydration over HPA catalysts in a steady-state flow system occurs via the surface-type rather than bulk-type catalysis as suggested hitherto. This follows from a strong correlation between the reaction rate and the number of surface proton sites in HPA catalysts.

Nowadays, fertilizers are used to boost crop production. Nitrogenous fertilizers are assimilated as nitrate. Unfortunately, 60–70% of nitrogen is lost due to different leaching processes. Photocatalytic urea oxidation is now emerging as a new methodology. Nitrate conversion is favorable under alkaline pH. However, it can subsequently cause deprotonation of ammonium ions to result ammonia leaching. In this report, efficiencies of bare and RGO loaded TiO2 were examined. In the presence of NaF, the nanocomposite possesses a 9.8(1)% nitrate yield, significantly greater than the other analogous reactions. Such observation will be helpful in developing new methodologies to afford sustainable agriculture.

We demonstrate the effect of two preparation methods of gold catalysts (<1 wt%) –colloidal method, Au(CM), and deposition-precipitation, Au(DP)– and three pretreatments on the activity of Ce0.8Fe0.2O2-supported catalysts in the NO-SCR by CO. Au(CM) (Tlight-off = 256 °C) displays activity inferior to the support (Tlight-off = 186 °C) after all pretreatments, attributed to surface composition and stable‑carbonate formation. Au(DP) pretreated with O2 at 200 °C (Tlight-off = 82 °C) displays activity higher than the support. Auδ+-OH sites were evidenced by XPS and DRIFTS on Au(DP), key to converting CO to CO2 at lower temperatures, in turn, producing oxygen vacancies, responsible for reducing NO to N2.

As a material with multifunctional ligands, metal-organic frameworks (MOFs) can effectively regulate the electronic and geometric state of supported metal nanoparticles (MNPs). Herein, a strategy of PtCo alloy incorporated into UiO-66-NH2 hybrid nanoparticles by a facile one-pot solvothermal method was developed. A series of PtCoy@UiO-66-NH2 materials with different Co/Pt ratios were successfully synthesized using CoO as the cobalt source. The obtained PtCo0.80@UiO-66-NH2 exhibited excellent conversion (94.3%) with high selectivity (93.3%) for selective hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL). Moreover, the formation rate of COL achieved to 5 mol·gPt−1·h−1 as Co/Pt atomic ratio was higher than 0.41. The synergistic effect of Pt, Co and UiO-66-NH2 was investigated by various characterizations. The results revealed that the Lewis acid CoNx favored the linear adsorption of CO bond, and PtCo alloy enhanced activity and selectivity by lowering the activation barrier for CO bond activation and simultaneously suppressing adsorption of CC bond.

Perchloroethylene (PCE) is a pollutant toxic to aquatic life and suspected of being a human carcinogen. It is also recalcitrant to degradation. Therefore remediation of PCE-contaminated groundwater is currently still a challenging task. In this work, the efficiency of a UV-assisted oxidation process exploiting a photocatalyst composed of zero-valent iron supported on commercial zinc sulfide (Fe/ZnS) and incorporated in a highly porous polymer, is investigated. The experimental studies were carried out, for about six months, on a pilot-scale photoreactor operating in continuous mode at the Solofra (Campania, Italy) wastewater plant, to evaluate the effectiveness and stability of the photocatalytic system. The results show that it is possible to reach a PCE degradation in natural groundwater in the range of 85–95%%. Furthermore, a kinetic model is developed and compared with collected experimental data. The mathematical model well describes the experimental data of the photocatalytic system operating both in batch and continuous mode and therefore it can be potentially used for further scale-up of photocatalytic systems devoted to PCE degradation, allowing to estimate the catalyst weight required for total PCE removal as a function of the liquid flow rate to be treated and inlet PCE concentration.

A facile hydrothermal process was used to prepare peanut shells derivatives (PS)-supported MoS2 nanosheets (PS-MoS2), which showed much better hydrogen evolution reaction (HER) catalytic activity than MoS2. PS-MoS2 displayed excellent catalytic performance with lower onset overpotential (94.5 mV) and good cyclic stability. By analyzing the results of characterization of superficial properties, structure, morphological, and elemental valence state, 11.1%-PS-MoS2 exhibits exceptional catalytic activity due to an effective increase in the amount of exposure of active sites and in the content of lower valence Mo and S with higher HER activity owing to the addition of PS.

Our study provides valuable insights into the photoinduced degradation of nadolol in the Danube River through catalytic oxidation with radicals. The presence of H2O2 under UV and UV-LED irradiation significantly enhanced degradation efficiency. The water matrix complexity had a significant impact on process efficiency. Nitrate, chloride, and sulfate ions exhibited an inhibitory effect on nadolol degradation by quenching •OH radicals. Additional analyses, including catalase activity, lipid peroxidation, and computational analysis, revealed proposed degradation intermediates. Six degradation intermediates were proposed, along with their NMR chemical shifts. The degree of mineralization and in vitro toxicity were assessed.

Microporous ammonium phosphomolybdate (APM) as a catalyst is used to degrade tetracycline (TC) antibiotics under ambient conditions. APM is prepared and characterized. The microporosity and high surface area of the APM and Mo+6 present in it made it a useful catalyst for TC destruction in aerobic conditions. The Mo+6 present in APM is transformed to Mo+5 and the formed Mo+5 again is oxidized during the process. Singlet oxygen and hydroxyl radicals as reactive oxygen species are responsible for TC degradation. APM shows excellent stability and reusability. This is the first time, APM is exploited as a catalyst to degrade TC.

Piezoelectric catalysis has been considered a promising technology in water pollution control. In this report, environmental-friendly (Bi1/2Na1/2)(1-x)BaxTiO3(BNBT-x) piezoelectric materials with the morphotropic phase boundary (MPB) were prepared by one-step solvothermal method. The piezocatalytic activities of the BNBT-x piezoelectric materials were examined by the degradation of RhB dye solution. The results demonstrate that the BNBT-6 catalyst with the MPB exhibit a higher piezocatalytic performance of up to 98.95% compared to pure BNT. In addition, the BNBT-6 catalyst exhibits good reusability, which is of great significance for practical applications. This work opens a route to design and develops high-performance piezocatalysts.

Cu-Zn MOF derived Cu-ZnO@C catalysts were developed and investigated for glycerol conversion to lactic acid in nitrogen gas. Full conversion of glycerol with 83.2% of lactic acid selectivity was realized for the Cu-ZnO@C-1.4-750 catalyst for 1 h at 220 oC. The Cu-ZnO@C-1.4-750 catalyst could be reused for 5 runs without regeneration treatment and slight deactivation occurs. Various characterization techniques were adopted to characterize the used catalyst. The active sites are verified to be Cu0 and Cu+ species. The high activity and size stability of the Cu-ZnO@C-1.4-750 catalyst are ascribed to highly dispersed Cu0/Cu+ species, proper Cu-ZnO interfaces and C coating.

Bimetallic Ni-Cu catalysts supported on halloysite nanotubes with different metal contents (Hal-Ni80Cu20, Hal-Ni70Cu30, Hal-Ni42Cu58) were prepared and employed in the catalytic degradation of chitosan (CS). The relationship between catalytic performances of the catalysts with the different metal contents were studied. The highest catalytic activity was reported for Hal-Ni42Cu58 due to the higher proportion of the active Cu2+ in the catalytic degradation. Furthermore in Hal-Ni42Cu58, CuO persisted dominantly with Ni(OH)2 as compared to Hal-Ni80Cu20 where Cu(OH)2 was also available. Overall, the bimetallic-supported Hal catalysts displayed better catalytic activities than monometallic supported catalysts due to the synergistic effect between the metals.

This study focuses on the development of a highly efficient and environmentally friendly nanocatalyst for the sequestration of organic pollutants. Through a combination of the hydrothermal method and in-situ deposition technique, Fe3O4@CMC-Cu nanocatalyst was successfully synthesized as confirmed by XRD, FT-IR, and XPS analysis. This synthesized nanocatalyst displayed exceptional capabilities in reducing various organic contaminants, including p-NP, p-NA, o-NP, NB, MO, and MB. The findings illustrate that this nanocatalyst possesses immense potential for environmental remediation due to its magnetic nature, outstanding stability, eco-friendly nature, reusability, and remarkable effectiveness in catalyzing the reduction of organic contaminants.

The textural properties and surface chemistry of activated carbon support are commonly known to have influence on the catalytic performance of catalysts. Many authors have assessed the effect of textural properties and surface chemistry of activated carbon support in the deoxygenation of triglycerides. This review focuses on reconciling literature on the role/relevance of textural properties and surface chemistry of activated carbon support in deoxygenation of triglycerides into diesel-like hydrocarbons. It is revealed that different activated carbon (AC) exhibit distinct effects on the catalytic behaviors of the supported catalyst. The degree of influence of both textural properties and surface chemistry of AC support varies with the nature of the supported catalyst.

High-energy facets exposed nanotubular alumina as well as conventional alumina supported Pd catalysts were synthesized and applied to the selective hydrogenation of phenylacetylene. Novel alumina supported catalyst presented higher selectivity at complete conversion of phenylacetylene. This could be related to the well dispersion of Pd and strong metal-support interaction, which are the consequences of the unique structural properties of the crystal plane regulated alumina. It helps create more active sites for hydrogenation meanwhile facilitates the desorption of alkene and thus suppresses the excess hydrogenation towards ethylbenzene.

A set of catalysts based on the mixed Cu-Co oxide supported on a porous dealuminized metakaolinite was synthesized and evaluated in the partial oxidation of glycerol under greener conditions. The characterization results confirmed the formation of an inverse spinel structure (CuCo2O4) as the active phase. High glycerol conversion (70.6%) and selectivity to dihydroxyacetone (88.2%) were obtained at 80 °C and 1:2 glycerol:H2O2 molar ratio, after 4 h of reaction, using a metal load of 10 wt% on the support. The catalytic activity results suggest that this reaction is sensitive to the metal oxide particle size, but the selectivity is unaffected.