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This work shows for the first time that palladium chloride, PdCl2, can influence the sequencing of sol–gel reactions involving tetraethyl orthosilicate (TEOS). A three-step procedure was utilised to create porous silica materials: liquid-phase sol reaction, drying and calcination. Evidence from 1H Nuclear Magnetic Resonance (NMR) spectroscopy revealed that PdCl2 had negligible influence on liquid-phase sol–gel reactions. During drying, 29Si NMR data showed that the silica sols doped with PdCl2 underwent more condensation reactions than those without. Variations in parameters known to effect sol–gel reactions could not account for the magnitude of the observed changes. Evidence from differential scanning calorimetry indicates that palladium catalyses silica hydrolysis during the drying stage, which promotes condensation reactions. Despite being more condensed after drying, 29Si NMR analysis revealed that the palladium silica structure became less condensed (compared with non-doped silica) after calcination. It is hypothesised that the interaction between palladium oxide and silanol groups inhibits condensation during the calcination process. The differences in sol–gel bonding seems to have minimal influence on the porosity of the calcined materials, though the presence of palladium nanoparticles reduced the total pore volume. This work has important implications for the design and optimisation of porous palladium silica materials. It also challenges the common assumption that metal dopants do not interact with silica sol–gel reactions.

In this work, coconut shell activated carbon (CSAC) electrode was evaluated to remove copper ion via electrochemical processes. CSAC electrode and graphite were applied as the cathode and the anode, respectively. The reusability of the electrode, the effects of initial pH, applied voltage and initial concentration were studied. The electrochemical process was carried out for 3 h of treatment time, and the electrodes (anode and cathode) were separated by 1 cm. The results revealed that CSAC is proven as a reusable electrode to remove copper ion, up to 99% of removal efficiency from an initial concentration of 50 ppm after it had been used three times. From the observation, the removal efficiency was optimum at an initial pH of 4.33 (without any initial pH adjustment). The applied voltage at 8 V showed a higher removal efficiency of copper ion compared to at 5 V.

This study investigates the optimal operational conditions for oxidative degradation of methyl orange (MO) in heterogeneous Fenton-like reaction using iron-immobilized montmorillonite KSF (Fe-MKSF) composites. Central composite design (CCD) experiments were used to determine the effects of four operational variables; pH solution, catalyst dosage, concentration of H2O2 and initial concentration of methyl orange dye (MO) on the percentage of MO removal. Based on the analysis of variance (ANOVA), the model illustrated high correlation coefficient (R2) of 0.9589 which demonstrated approximately 96% of target function variation. The optimal operational conditions were found to be at 2.8 pH solution, 0.8g/L catalyst dosage, 15 mM H2O2 concentration and 25 mg/L MO initial concentration which subsequently resulted in 98% of MO removal. Moreover, the experimental values obtained were in good agreement with the values predicted from the model, with relatively slight differences of 1.24%. Such findings shown significant interaction between four operational variables towards MO removal during the heterogeneous Fenton-like reaction using Fe-MKSF composites.

Heterogeneous Fenton-like reaction has received considerable research attention as one of promising treatment methods in degrading recalcitrant organic pollutant. In recent years, iron immobilized-montmorillonite KSF (Fe-MKSF) catalyst displayed decent catalytic activity in degrading organic contaminants. Inspired by such performances, further understanding on the detailed structural properties as well as its’ catalytic activity were performed to gain further insights towards the influence of iron to clay ratio during the catalyst synthesis. Fe-MKSF catalysts were synthesized by impregnation-hydrothermal method at varies iron molarity to the clay ratio. A series of Fe-MKSF catalyst ranging between 10 until 50 molarity of iron/clay ratio as well as pristine MKSF and iron oxide were characterized using nitrogen sorption and XRD analysis. The catalytic performance of resultant Fe-MKSF catalysts were tested for the oxidative degradation of methyl orange (MO) in heterogeneous Fenton-like reaction. At pH 3, 0.2 g/L Fe-MKSF, 12 mM of hydrogen peroxide and 25 mg/L MO’s initial concentration; Fe-MKSF-20 exhibited with exceptional performance of 85% removal. Such behavior was attributed to the high surface area (SBET=105.76 m2/g) and pore volume (0.39 cm3/g) of Fe-MKSF-20 compared with others iron/clay ratio. Moreover, form the XRD analysis, it was found that the immobilized iron on the MKSF was in hematite phase for all Fe-MKSF catalysts. In conclusion, the iron/clay ratio plays vital role in modulating the structural properties, which directly corresponded to the resultant catalytic activity of Fe-MKSF

Combination of Fenton-like reaction with heterogeneous catalyst has been recognized as effective way in removing persistence organic pollutants. Fe3-xCoxO4 catalyst has been considered as potential heterogeneous Fenton-like catalyst by substituting cobalt into the magnetite structure. In this study, details investigation on the effect of cobalt substitution in relation with catalytic performance of resultant catalyst was performed. The Fe3-xCoxO4 catalysts were synthesized through oxidation-precipitation method. The cobalt loading were varied at cobalt substitution value (x) of 0, 0.1, 0.2, 0.4 and 0.6, respectively. Interestingly, Fe3-xCoxO4 catalyst with x value of 0.4 has shown enhanced catalytic performance closed to 31% removal. The presence of cobalt led to the increased in catalytic activity by 17% as well as significant shift in the isoelectric point compared to the pristine catalyst (x=0). Moreover, the isoelectric point for Fe3-xCoxO4 at x=0 and x=0.4 were 5.00 and 8.44. This can be well described by the changes on resultant catalyst’s surface properties that led to enhance adsorption of AO7 molecules onto catalyst surface. The adsorbed AO7 molecules within the immediate vicinity of active sites were degraded rapidly by the generated interfacial hydroxyl radicals (•OH). Hence, such findings suggested that the substitution of cobalt provide positive influence in enhancing the redox activity of the resultant catalyst during the Fenton-like reaction

Cobalt ferrite catalysts (Fe3-xCoxO4) were synthesized by substituting cobalt into the structure of iron oxide via oxidation-coprecipitation method. Two types of precipitating agent (strong and weak base) were utilised at different molarity (1M, 3M and 5M) during the synthesis. NaOH and NH4OH were used as strong base and weak base, respectively. The resultant catalysts were further tested for its catalytic activity in the oxidative degradation of acid orange 7 (AO7). It was found that 43% of dye removal was obtained for the catalyst synthesized using 1M NaOH solution. Meanwhile on 20% of dye removal was observed for weak base at the similar concentration. Such differences could be corresponded to the differences in structural formation of resultant Fe3-xCoxO4 catalyts. The pore volume of catalyst synthesized by strong base comprised of 18% higher compared to the weak base; which may lead to better accessibility of pollutants directly to the active sites during the catalysis. In addition, the formation of synthesized catalyst from the strong base exhibited with crystalline phase; whilst amorphous for the weak base. Hence, it can be concluded that the used of strong base precipitating agent provides modest influence during the catalyst’s formation which directly affecting the overall catalytic performance of the Fe3-xCoxO4 catalyst during the Fenton-like reaction

Perovskite is known as potential decent ceramic metal oxides catalyst for wastewater treatment particularly in catalytic oxidation process. Perovskites can be uniquely and chemically tailored due to its simple structure which able to accommodate wide range of A and/or B-site cations. In this work, detailed investigations on the substitution effect of different B-site cations into the main structure of perovskite compounds towards catalytic oxidation of orange II solution were performed. Four (4) different types of B-site metal cations (Cu, Ni, Mo and Co) were substituted into perovskites structure via a combined EDTA-citric acid complexation method. The reactivity of resultant perovskites was found to be in sequence of Na0.27Ca0.48Cu0.25O3 > Na0.25Ca0.48Ni0.27O3 ≍ Na0.09Ca0.29Mo0.62O3 > Na0.02Ca0.33Co0.39O3 in the absence of stimulant or oxidant during 2 hours heterogeneous reaction. Interestingly, Na0.09Ca0.29Mo0.62O3 perovskites catalyst exhibited superior catalytic activity by having complete Orange II removal (≍99%) in the presence of oxidant (0.022M H2O2) within 15 min of reaction. The reactivity of B-site perovskites catalysts changed significantly in presence of oxidant during heterogeneous reaction that can be represented as Na0.09Ca0.29Mo0.62O3> Na0.27Ca0.48Cu0.25O3>Na0.02Ca0.33Co0.39O3>Na0.25Ca0.48Ni0.27O, respectively. Such findings confer tunable and unique catalytic properties of B-site perovskites catalysts in enhancing the oxidative degradation of recalcitrant dye contaminated wastewater effluents.

In this research, the activated carbon prepared from tropical plant waste based Casuarinas Equisetifolia plant was activated through chemical activation by using potassium hydroxide (KOH) as the activating agent. The raw sample was carbonized following conventional heating via electric furnace at 600˚C with the increasing temperature 30˚C/minutes in one hour which was selected as the optimum condition. The prepared activated carbons exhibit mesoporous with the pore diameter within 0.2 µm to 20 µm. From the Scanning Electron Microscopy (SEM) micrographs, the morphology of the activated carbon indicated that they demonstrated high pore development on it surfaces. The effects of initial pH, contact time and adsorbent dosage onto the adsorption performances were evaluated through batch adsorption study. The COD removal increased when the adsorbent dosage was increased. The adsorption of COD and colour were best fitted by the Freundlich isotherm model compared to ammonia, which the correlation regressions, R2 ...

In this work, montmorillonite KSF clay was used to immobilize iron species as a potential heterogeneous UV assisted Fenton-like reaction. Iron-immobilized MKSF (Fe-MKSF) was synthesized via hydrothermal method in an autoclave. Fe-MKSF was tested on methyl orange (MO) removal by adsorption (5%) and hydrogen peroxide (H2O2) activation (63%) and these prominent margins proved Fe-MKSF performance was attributed by UV assisted Fenton-like reaction. Fe-MKSF show superior performance with 63% color removal within 180 mins reaction in comparison to iron oxide and pristine MKSF. The Fe-MKSF increased in the surface area from 91.1 to 101.9 m2/g and pore volume from 0.13 to 0.45 cm3/g compared to pristine MKSF. The SEM images of Fe-MKSF show iron aggregates indicating successful immobilizing process and the elemental weight percent of iron which increase from 6.12% to 55.38% in Fe-MKSF. These findings prove Fe-MKSF as a promising alternative catalyst in dye contaminated wastewater treatment.

Gold nanoparticles (AuNPs) are considered as one of the most stable metal nanoparticles and have received immense research’s interest due to their size-related electronic, magnetic and optical properties such as quantum size impact. However, AuNPs tend to form agglomeration in solution. Hence, detailed study on colloidal stability is crucial in preventing the agglomeration of AuNPs. The AuNPs was prepared by using sodium citrate reduction method before dispersing the sample in the organic media, dimethylformamide (DMF) prior to transmission electron microscopy (TEM) and Zeta Sizer analysis. The AuNPs were also dispersed in aqueous media which subsequently being characterized using UV-Vis spectroscopy and Zeta Sizer analysis. The effect of temperature was investigated in order to identify the hydrodynamic size and the stability of the AuNPs in both DMF and aqueous media. The presence of AuNPs in solution was confirmed by the maximum absorbance peak at the wavelength of 552 nm. From the TEM analysis, the AuNPs were dispersed well in the organic media which the nominal particles size distribution centered at 3.5 nm. The optimum temperature for AuNPs in both organic and aqueous media was at ≤ 35 °C where the zeta potential showed -30.7 mV and -36.7 mV respectively. From the observations on hydrodynamic particles size, it was shown that the particles size had the smallest size of 20 nm at 25°C and biggest size of 132 nm at 55°C in aqueous media. While particles size in DMF showed, the smallest size and biggest size were 36 nm at 25°C and 158 nm at 55°C, respectively. Thus, the AuNPs in aqueous media showed comparatively smaller size of particles compare to the AuNPs in DMF.

Well-dispersed iron oxide nanoparticles supported onto graphene oxide sheets (i.e. GO–Fe 3 O 4 nanocomposite) were synthesised and used as heterogeneous Fenton-like catalyst for the degradation of Acid Orange 7 dye (AO7). The reaction was systematically investigated under various experimental conditions such as nanocomposite dosage, pH, temperature, oxidant and dye concentrations. Best results showed a fast 80% degradation in ∼20 min, whilst ∼98% of AO7 was successfully removed after 180 min of reaction time. The degradation kinetics of AO7 was most influenced by pH and temperature, and can be described by a pseudo-first-order reaction following the Langmuir–Hinshelwood mechanism. Analysis of the spent nanocomposite suggested that the phase of iron oxide nanoparticles remained unchanged whilst minor pore volume losses occurred via carbon deposition and/or re-stacking of GO sheets.

This work presents a facile, scalable method for the fabrication of graphene oxide-iron oxide (GO-FeO) nanocomposites produced by co-precipitation of iron ions onto the GO surfaces in basic aqueous media. FTIR and XRD characterisation suggests that FeO was chemically anchored to the GO sheets, possibly via the carboxyl and hydroxyl groups. Small GO loadings of 0.5 and 1 wt% were not sufficient to alter the FeO structures. However, increasing the GO loading to 5 and 10 wt% resulted in significant loss in pore volume, thus suggesting the lamellar GO sheets decorated with FeO were assembling into GO-FeO nanocomposite stacks. It was found that the GO-FeO nanocomposites had an enhanced catalytic activity in the heterogeneous Fenton-like oxidation of Acid Orange 7 (AO7) compared to pure GO flat sheets and FeO nanoparticles. Interestingly, the GO-FeO nanocomposite with 5 wt% loading ratio exhibited the best catalytic activity with 76% degradation of AO7 dye observed within 90 min of reaction. This was attributed to the synergistic effect of GO by enriching the adsorbed AO7 molecules onto the nanocomposite to be further oxidised in the vicinities of active sites. This finding suggests the promising employment of GO-FeO nanocomposites in removing organic dyes from polluted water by heterogeneous Fenton-like reaction.

The selection of a good catalyst support is crucial in contributing towards the enhancement catalytic activity of a catalyst. Therefore, in this study, the influence of montmorillonite KSF (MKSF) clay loading in relation with catalytic performance of the resultant composite catalyst has been investigated. The MKSF clay loading were varied at x = 20, 40, 60 and 80 wt%, respectively. Interestingly, Fe3-0.3Mn0.3O4-MKSF(40wt%) has shown greater catalytic performance up to 98% of acid orange II (AOII) dye removal in comparison to the Fe3-0.3Mn0.3O4 and Fe3O4 catalysts. The AOII degradation kinetic using Fe3-0.3Mn0.3O4-MKSF(40wt%) was fitted well with first-order reaction kinetic and the reaction rate increased in the order of Fe3O4>Fe3-0.3Mn0.3O4>Fe3-0.3Mn0.3O4-MKSF(40wt%). It also demonstrated in the work that Fe3-0.3Mn0.3O4-MKSF(40wt%) catalyst can be reused several times without affecting its efficiency. Thus, it can be suggested that MKSF clay as catalyst support played a significant role in enhancing the overall catalytic performance of Fe3-0.3Mn0.3O4 catalyst during the heterogeneous Fenton-line reaction as well as the degradation kinetics of the AOII solutions.

For many years, Southeast Asia region encountered several ongoing air pollution episodes. These episodes had indirectly significant impact on the air quality of neighboring countries. Hence, this study aims to assess the characteristics and trend of air pollution in Malaysia particularly at Langkawi Island. Air pollution hourly monitoring records from 2003 to 2017 were used in analyzing the statistical data analysis. Eight parameters were selected in this study which known as PM10, CO, SO2, NO2, O3, relative humidity (RH), temperature (T) and wind speed (WS). The results showed that the hourly trends of PM10, CO, SO2, NO2 and O3 in Langkawi Island were below the MAAQG standard. The results also indicated that dispersion of PM10 in Malaysia were significantly affected by temperature, wind speed and relative humidity.

In this work, detailed investigation on the optimization of acid orange II (AOII) degradation using Fe3-xMnxO4 catalyst in UV assisted Fenton-like reaction was performed. The Central Composite Design (CCD) based on Response Surface Methodology (RSM) with four independent operational parameters (catalyst dosage, oxidant concentration, pH and UV irradiation) and one response (percentage of AOII removal) was applied for statistical and optimization analysis. The maximum AOII removal (~100%) was found at optimal conditions of 0.4 g/L catalyst dosage, 35 mM oxidant concentration, pH 2.6 and 3 x 9W UVC. Interestingly, validation of these optimal conditions was confirmed by the experimental findings of having less than 2% absolute deviation. Such findings confer that the derived empirical quadratic model was in good agreement with the experimental findings.

This work presents the iron oxide recovery from electric arc furnace slag with different temperature and time using acid leaching method. The results showed that formation of iron oxide from electric arc furnace (IO-EAFS) was influenced by the temperature and time of heating. This is evidenced by constant acid concentration and liquid to solid ratio, 5 hours of heating time was exhibited the highest amount of iron ion in extracted solution. The maximum of iron extract in heating temperature was at 100 °C. Throughout the characterization using Scanning Electron Microscopy (SEM), the iron oxide illustrated the microstructures were agglomerates predominantly with irregular shapes and XRD results further colobrated the presence of hematite combined with other metal oxide exists in the IO-EAFS. From the TGA analysis, it was identified that the recovered iron oxide was totally decomposed at 525°C. This results indicate that electric arc furnace slag is potential material of iron oxide for the future appliction.

In this study, the influence of manganese substitution on the photocatalytic activity of heterogeneous Fe3-xMnxO4 catalyst were investigated. The Fe3-xMnxO4 catalysts were synthesized through co-precipitation method at varies manganese (Mn) substitution ratio (x) of 0, 0.1, 0.2, 0.3, 0.4 and 0.5, respectively. The photocatalytic performance of the resultant catalysts were tested in photo Fenton-like degradation of AOII dye in the presence of 22Mm H2O2 at initial pH of 3. Interestingly, discoloration of 95.9% AOII was achieved at optimized x value of 0.3. Enhancement of nearly 98% was observed compared to pristine catalyst (x=0) which was able to degrade up to 48.4% only. In addition, it also demonstrated that the AOII degradation kinetic using Fe3-xMnxO4 catalyst at x=0.3 by photo Fenton-like reaction was fitted well with the first order reaction kinetic (k = 0.018 min-1 and R2 = 0.9862). Thus, it can be suggested that the substitution of Mn into the matrix of iron oxide provides a positive influence in enhancing the overall photocatalytic peformance of heterogeneous Fe3-xMnxO4 catalyst during the photo Fenton-like reaction.

Owing to the electron donor-acceptor properties of GO, the active sites ([triple bond, length as m-dash]Fe(2+)) of Fe3O4 are not oxidised ([triple bond, length as m-dash]Fe(3+)) in the heterogeneous Fenton-like reaction. GO plays a sacrificial role via the oxidation of (C[double bond, length as m-dash]C) carbon domains, and transferring electrons to Fe3O4. Therefore, GO-Fe3O4 confers superior catalytic efficiency, recyclability and longevity, otherwise not available in Fe3O4.

In this work, a series of zinc partially substituted magnetite nanoparticles (Fe3-xZnxO4, 0 ≤ x ≤ 0.4), were synthesised through a facile precipitation-oxidation method. The partial substitution of zinc into the magnetite (Fe3O4) structure was confirmed by the collective findings of nitrogen sorption, XRD and TG-DTG analysis. It was found that the partial substitution of zinc slightly changed the textural properties of the resultant Fe3-xZnxO4 nanoparticles. From the XRD analysis, there was no visible formation of secondary phase or impurity peaks in the nanoparticles. These findings indicated the partial substitution of zinc into the Fe3O4 crystal structure with a good dispersion within the Fe3O4 matrix. © 2016 Author(s).

International audience; A series of graphene oxide (GO) and zinc partially substituted magnetite GO-Fe1-xZnxOy (0 ≤ x ≤ 0.285) catalysts were synthesised through a precipitation-oxidation method. The rate constants for the degradation of acid orange seven (AO7) proceeded at a significant faster rate under UV-irradiation (up to 670%) than the conventional heterogeneous Fenton-like reaction. The resultant catalysts were mesoporous, so there was no mass transfer limitation for AO7 to access active sites in the catalysts. Further, maximum increases of rate constant up to 220% occurred as the zinc molar concentration increased from x = 0 to x = 0.159. GO enhanced to incorporation of zinc into the combined metal oxide, whilst zinc limited crystal growth, thus forming smaller crystallite sizes. These features proved to be essential for the improved catalytic activity of the resultant catalysts. The optimised zinc molar value at x = 0.159 delivered the best catalytic activity. © The Royal Society of Chemistry 2016.

Iron–immobilized montmorillonite KSF (Fe-MKSF) has been recognized as promising catalyst in degrading persistence organic contaminants. However, detailed mechanistic insight during the catalysis which involving the formation and identification of radical species were remained indeterminate due to complex reaction. Inspiring by this gap, iron-immobilized clay (Fe-MKSF) was synthesized and used as heterogeneous catalyst in the oxidative degradation of methyl orange (MO) solution. Identification of radical species were determined through the inclusion of different types of radical scavenging agent during the Fenton-like reaction at optimum condition. Interestingly, dominant radical species were found to be hydroperoxyl radicals (•OOH) which subsequently followed by hydroxyl radicals (•OH) during the catalysis. Based on the percentage of MO removal, it was suggested that approximately 88% of the •OOH radicals existed at the interface of catalyst while 39% presence in bulk solution. Meanwhile, the interface •OH radicals promoted 38% of MO removal, whilst 4% by the bulk •OH radicals. Hence, these findings have conveyed novel insight on detailed radicals' identification as well as its' interaction during the catalysis.

The development of active and stable heterogeneous Fenton-like catalysts have emerged as an alternative to overcome the practical limitations related to the homogeneous Fenton catalyst, where various iron species and/or iron oxides are immobilised within the structure of different catalyst supports. Clay, alumina, zeolite and carbonaceous materials such as activated carbon and carbon nanotubes have been used as catalyst supports of choice by the scientific community. However, there is a knowledge gap associated with using high aspect ratio 2D (dimension) graphene oxide (GO) as an alternative catalyst support. Of particular interest, it is postulated that the structure and functionalities of GO as a support confers to the resultant catalyst overall catalytic activity beyond the conventional Fenton catalysts. In this thesis, the structural and physicochemical properties of resultant catalyst with their corresponding catalytic activity were systematically investigated. To this end, the synergistic interaction between GO and immobilised iron oxide nanoparticles (Fe3O4 NPs) was proposed for an oxidative degradation of synthetic dye acid orange 7 (AO7), which is a major water pollutant from textile production. The GO‒Fe3O4 nanocomposites were initially synthesised through a facile one-pot method by co-precipitating irons salts onto GO sheets in a basic solution. The formation of GO‒Fe3O4 was postulated as follows: (i) Fe3+/ Fe2+ ions are adsorbed and coordinated by the carboxyl groups (C=O) of GO sheets, (ii) hydrolysed ions form nanoclusters on GO sheets when NaOH is introduced, (iii) followed by condensation of the nanoclusters to form Fe3O4 nuclei, and (iv) further nucleation and growth of Fe3O4 crystallites on GO sheets were due to the redox reaction as the pH is increased to 10. The incorporation of GO led to an enhancement on the catalytic activity of the nanocomposites with 76% AO7 removal over the control catalysts of Fe3O4 NPs and GO sheets, which corresponds to 48 and 22%, respectively. Further improvements on the catalytic activity of GO‒Fe3O4 were performed by modifying the synthesis through pre-hydrolysing iron salts prior to GO addition at pH 4 with various GO loadings. The key finding of this new method is the formation of two sets of different mesoporous structure. At low GO loadings ≤10 wt%, GO–Fe3O4 nanocomposites resulted in high surface area up to 409 m2 g-1, in tandem with high 92‒98% degradation of AO7. By contrast, GO loadings >10 wt% led to reduced surface area and lower GO‒Fe3O4 activity (60%). The presence of strong interfacial interactions (Fe–O–C bonds) in the nanocomposites contributed to the superior degradation of AO7, in tandem with structural-morphological features. The operational conditions of heterogeneous Fenton-like reaction were evaluated and modelled as a function of nanocomposites dosage, pH, temperature, oxidant and dye concentrations. Best results showed a fast 80% degradation in ~20 min, whilst ~98% of AO7 was successfully removed after 180 min of reaction time. Optimal conditions were determined for nanocomposites (GO(5wt%)‒Fe3O4) at the catalyst dosage of 0.2 g L-1, initial pH of 3 and 22 mM of H2O2 concentration at 298 K. The kinetics for the oxidative degradation of AO7 was found to be a pseudo-first-order reaction following the Langmuir-Hinshelwood mechanism. A noteworthy finding was the high activity (>98%) and recyclability of GO‒Fe3O4 over 7 cycles whilst the Fe3O4 NPs exhibited a severe loss of activity (~0%) at the 5th cycle. It was found that the ratio of Fe3+/Fe2+ for GO‒Fe3O4 remained almost constant over the 7 cycles, contrary to Fe3O4 NPs which underwent a significant Fe2+ decrease. The synergistic effect of GO in the GO‒Fe3O4 nanocomposite was able to accelerate the ≡Fe3+/≡Fe2+ redox cycles for the fast reduction of ≡Fe3+ to ≡Fe2+ which is actively participating in the decomposition of adsorbed H2O2 into HO• radicals during catalysis. The X-ray photoelectron spectroscopy (XPS) analysis of spent GO‒Fe3O4 showed that the sp2 carbon domains (C=C) slightly decreased after every cycle, thus suggesting some degree of oxidation of the carbon basal plane. It is therefore postulated that the unusual stability in the GO‒Fe3O4 is attributed to a donor-acceptor mechanism of the nanocomposites, in which the electrons donated from the oxidation of the GO are used for the regeneration of ≡Fe2+ and thus maintaining the Fe3+/Fe2+ ratio. Finally, the partial substitution of zinc (Zn) into Fe3O4 in the presence of GO was investigated, in view of the UV photocatalyst properties of zinc oxides. A slight change on the physicochemical properties of GO–Fe3-xZnxO4 lead to an increase in photocatalytic activity, where x=0.2 gave the higher degradation of AO7 in the UV-assisted Fenton-like reactions at 60 min reaction. It was found that the activity of the catalyst without GO always gave lower values ~30% of AO7 removal. Therefore, GO has proven again its beneficial use as an active component in the case of UV-assisted Fenton-like reaction as well.

Polymer electrolyte pore-filled membranes, for possible use in direct methanol fuel cells (DMFCs), have been prepared by radiochemical grafting of styrene into porous poly(vinylidene fluoride) (PVDF) films using simultaneous irradiation with an electron beam (EB) followed by a sulfonation reaction. The physico-chemical properties of the obtained polystyrene sulfonic acid pore-filled membranes are evaluated using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), ac impedance, and a methanol diffusion cell. The effects of variation of the grafting yield (Y%) on the ionic conductivity and the methanol permeability of the membranes are investigated. The ionic conductivity of the membranes increases with increase in Y% and exceeds that of the perfluorinated ionomer membrane, Nafion 117, at a grafting yield of 46%. The methanol permeability of 40 and 46% pore-filled membranes is lower than that of Nafion 117 by 53 and 71%, respectively. The performance characteristic factor suggests that these membranes are potential candidates for DMFC applications.

Polystyrene sulfonic acid (PSSA) pore-filled poly(vinylidene fluoride) (PVDF) membranes have been prepared using simultaneous electron irradiation method. Porous PVDF films were grafted by pre-swelling in styrene solution and subsequent irradiation with an electron beam (EB) under nitrogen atmosphere and at ambient temperature. The grafted films i.e. polystyrene (PS) pore-filled PVDF were subsequently sulfonated with a diluted mixture of chlorosufonic acid. The effects of the reaction parameters on the content of PS grafted in the pores of PVDF films were investigated. The chemical and morphological properties of the membranes in comparison with their un-grafted and grafted counterparts were studied by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The transport properties of these membranes such as ionic conductivity and methanol permeability were evaluated and correlated with the content of PS grafted in the pores of the PVDF films. The PSSA pore-filled PVDF membranes with PS content in the pores of 40% and above showed superior performance characteristics compared to Nafion 117 membrane and therefore can be potential alternatives to improve the performance of direct methanol fuel cell (DMFC).

Pore-filled polymer electrolyte membranes have been prepared as a potential proton exchange membrane by radiation induced grafting using simultaneous technique. The porous substrate films were grafted in a subsequent step after flooding the membranes pores with styrene monomer. The grafted films were then sulfonated in a post-grafting reactions. The influence of grafting conditions, i.e. irradiation dose and monomer concentration in correlation with the grafting yield ( Y ) have been investigated. The results showed that the grafting yield is increased for both conditions. The resulting membranes were then characterized by evaluating their physico-chemical properties such as ion exchange capacity, water uptake and proton conductivity as a function of grafting yield. The overall results showed that polystyrene grafts is successfully anchored within the pores of PTFE films during grafting and subsequently transformed into hygroscopic proton exchange regions after being sulfonated. The measured conductivity of the sulfonated polystyrene pore-filled electrolyte PTFE membranes achieved were approximately within the magnitude of 10 −3 and 10 −2 S cm −1 at room temperature and at higher operating temperature, respectively.

International audience; Abstract View references (45)Graphene oxide-iron oxide (GO-Fe3O4) nanocomposites were synthesised by co-precipitating iron salts onto GO sheets in basic solution. The results showed that formation of two distinct structures was dependent upon the GO loading. The first structure corresponds to a low GO loading up to 10wt%, associated with the beneficial intercalation of GO within Fe3O4nanoparticles and resulting in higher surface area up to 409m2g-1. High GO loading beyond 10 wt% led to the aggregation of Fe3O4 nanoparticles and the undesirable stacking of GO sheets. The presence of strong interfacial interactions (Fe-O-C bonds) between both components at low GO loading lead to 20% higher degradation of Acid Orange 7 than the Fe3O4 nanoparticles in heterogeneous Fenton-like reaction. This behaviour was attributed to synergistic structural and functional effect of the combined GO and Fe3O4 nanoparticles.

Sulfonated polystyrene pore-filled electrolyte membranes have been prepared by simultaneous radiation grafting of styrene into porous poly(vinylidene fluoride) (PVDF) films and subsequent sulfonation process. The effects of two-step membrane preparation procedures and grafting yield on the thermal stability and structural properties of membranes were investigated by thermal gravimetric analysis and differential scanning calorimetry, respectively. A three-step degradation pattern was observed from TGA thermograms of all the membranes, which attributed to the dehydration, desulfonation, and degradation of the PVDF backbone. The weight losses in the membranes were found to be reliant on the grafting yield. Meanwhile, the intrinsic crystallinity of the PVDF matrix was found to show a decreasing trend with increasing in grafting yield. A further decrease in crystallinity was also observed in the sulfonation reaction. The residual crystallinity of the PVDF matrix approximately 5% was still remained in the membranes even it had been subjected to severe reaction conditions. The decreased in crystallinity of the resulting membranes can be explained by the combination of the dilution effect and the crystal disruption that occurred within the membrane's matrix.

The scope of this chapter is to give a brief introduction about fuel cells, types of applications in fuel cell technology, characteristics of fuel cells, potential applications in fuel cell technology, and current research and development and key technology players in fuel cells.