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We report on the synthesis of SnO2 nanoparticles and SnO2:CNT hybrids, via a one-step solgel method. Herein, we investigate the influence of the synthesis conditions on their physical, chemical, optical and electrochemical properties. The crystalline structure, nanoparticle size and morphology are assessed by X-ray diffraction and transmission electron microscopy. The chemical states are elucidated by X-ray photoelectron and Raman spectroscopies. Their electrochemical behavior is studied by cyclic voltammetry. Overall, an oxygen-poor environment during the synthesis leads to smaller SnO2 nanoparticles, along with an increased number of surface defects. Photoluminescence spectroscopy demonstrates that under an oxygen-poor environment, bridging-oxygen vacancies are more abundant. Additionally, SnO2 nanoparticles containing a higher amount of oxygen vacancies exhibit a higher cycling stability of 90%. The cycling stability is further enhanced in hybrid SnO2:CNT. The electrochemical behavior is corroborated to the surface defects and in turn, the band bending mechanism in SnO2 n-type semiconductor. [ABSTRACT FROM AUTHOR]

34685052 2 Rauwel P., Galeckas A., Rauwel E. Enhancing the UV Emission in ZnO-CNT Hybrid Nanostructures via the Surface Plasmon Resonance of Ag Nanoparticles. The second publication, by Rauwel et al., reports on the combination of ZnO nanoparticles with CNT and Ag nanoparticles, and emphasizes the plasmonic effect of Ag nanoparticles in the enhancement of UV emission owing to the Burstein-Moss effect [[2]]. The second publication by Paredes et al. describes the one-step synthesis of nanoparticle mixtures of Cu-Cu SB 3 sb N-Cu SB 2 sb O and their potential in the sunlight-driven photocatalytic degradation of azo dyes [[9]]. [Extracted from the article]

Dopant-defect reactions dominate the defect formation in mono-crystalline ZnO samples implanted with Ag and B ions. This is in contrast to most other ion species studied and results in an enhanced concentration of extended defects, such as stacking faults and defect clusters. Using a combination of B and Ag implants and diffusion of residual Li atoms as a tracer, we demonstrate that extended defects in ZnO act as efficient traps for highly mobile Zn interstitials. The results imply that dynamic annealing involving interaction of point defects with extended ones can play a key role in the disorder saturation observed for ZnO and other radiation-hard semiconductors implanted with high doses. [ABSTRACT FROM AUTHOR]

Photoluminescent ZnO carbon nanomaterials are an emerging class of nanomaterials with unique optical properties. They each, ZnO and carbon nanomaterials, have an advantage of being nontoxic and environmentally friendly. Their cost-effective production methods along with simple synthesis routes are also of interest. Moreover, ZnO presents photoluminescence emission in the UV and visible region depending on the synthesis routes, shape, size, deep level, and surface defects. When combined with carbon nanomaterials, modification of surface defects in ZnO allows tuning of these photoluminescence properties to produce, for example, white light. Moreover, efficient energy transfer from the ZnO to carbon nanostructures makes them suitable candidates not only in energy harvesting applications but also in biosensors, photodetectors, and low temperature thermal imaging. This work reviews the synthesis and photoluminescence properties of 3 carbon allotropes: carbon quantum or nanodots, graphene, and carbon nanotubes when hybridized with ZnO nanostructures. Various synthesis routes for the hybrid materials with different morphologies of ZnO are presented. Moreover, differences in photoluminescence emission when combining ZnO with each of the three different allotropes are analysed. [ABSTRACT FROM AUTHOR]

Silver has been recognized as a nontoxic, safe inorganic antibacterial/antifungal agent used for centuries. Silver demonstrates a very high potential in a wide range of biological applications, more particularly in the form of nanoparticles. Environmentally friendly synthesis methods are becoming more and more popular in chemistry and chemical technologies and the need for ecological methods of synthesis is increasing; the aim is to reduce polluting reaction by-products. Another important advantage of green synthesis methods lies in its cost-effectiveness and in the abundance of raw materials. During the last five years, many efforts were put into developing new greener and cheaper methods for the synthesis of nanoparticles. The cost decrease and less harmful synthesis methods have been the motivation in comparison to other synthesis techniques where harmful reductive organic species produce hazardous by-products. This environment-friendly aspect has now become a major social issue and is instrumental in combatting environmental pollution through reduction or elimination of hazardous materials. This review describes a brief overview of the research on green synthesis of silver metal nanoparticles and the influence of the method on their size and morphology. [ABSTRACT FROM AUTHOR]

Tin oxide (SnO2) is a versatile n-type semiconductor with a wide bandgap of 3.6 eV that varies as a function of its polymorph, i.e., rutile, cubic or orthorhombic. In this review, we survey the crystal and electronic structures, bandgap and defect states of SnO2. Subsequently, the significance of the defect states on the optical properties of SnO2 is overviewed. Furthermore, we examine the influence of growth methods on the morphology and phase stabilization of SnO2 for both thin-film deposition and nanoparticle synthesis. In general, thin-film growth techniques allow the stabilization of high-pressure SnO2 phases via substrate-induced strain or doping. On the other hand, sol–gel synthesis allows precipitating rutile-SnO2 nanostructures with high specific surfaces. These nanostructures display interesting electrochemical properties that are systematically examined in terms of their applicability to Li-ion battery anodes. Finally, the outlook provides the perspectives of SnO2 as a candidate material for Li-ion batteries, while addressing its sustainability. [ABSTRACT FROM AUTHOR]

Nominal Gd6WO12, Gd5.94Ca0.06WO12−δ, Gd5.7Ca0.3WO12−δ and Gd5.7WO12−δ were synthesized by solid state reaction and wet chemistry methods. The structure and morphology of the materials were analyzed by XRD, SEM and TEM and the electrical conductivity was measured as a function of temperature in reducing and oxidizing atmospheres under wet and dry conditions. The total conductivity is essentially independent of composition above 700°C. Below 700°C, the conductivity of Ca-doped samples is higher than that of Gd6WO12 and Gd5.7WO12−δ and increases with increasing doping concentration. The conductivity below 700°C is also higher under wet compared to dry conditions and, moreover, the H–D isotope effect on the conductivity is significant. Based on this, and on conductivity characterization as a function of and , it was concluded that the materials are mixed ionic and electronic conductors where electrons and holes dominate at high temperatures and intermediate temperatures under sufficiently reducing and oxidizing conditions, respectively. Protons are the predominating ionic charge carriers below approximately 700°C. The hydrogen flux through Gd5.7Ca0.3WO12−δ was measured as a function of temperature under wet and dry sweep gas conditions, as well as with varying on the feed side, confirming the picture outlined by the conductivity measurements. A defect chemical model has been derived to which the conductivity data were fitted yielding thermodynamic and transport parameters describing the functional characteristics of the materials. [ABSTRACT FROM AUTHOR]

Abstract: The binary Zn4Sb3 phase is a promising material for thermoelectric applications due to its extraordinarily low thermal conductivity. The present study attempts to rationalize this property by investigating its nanostructure. β-Zn4Sb3 samples with varying Zn content were thus synthesized, quenched from the melt and annealed at 350°C. Their nanostructure was observed using transmission electron microscopy. The samples presented in this work have Zn:Sb atomic ratios of 1.30 and 1.33 and exhibit a single phase of β-Zn4Sb3 in X-ray diffraction studies. Transmission electron microscopy (TEM) observations revealed nanoporous morphologies for both compositions, with a random distribution of the voids. Both samples contain voids, while the sample with Zn:Sb=1.33 also consists of Zn nanoinclusions. Density functional theory calculations were carried out to study the stability of atomistic β-Zn4Sb3 models with varying Zn content. This was used to suggest a mechanism for the formation of Zn nanoparticles and subsequently nanovoids. The calculations imply that the Zn solubility in the Zn4Sb3 matrix increases with decreasing temperature. Combined with a high Zn diffusivity, this work explains how Zn could leave the nanoprecipitates during annealing, resulting in the voids seen by TEM. [Copyright &y& Elsevier]

Abstract: Rare earth silicates with the structure of apatite are attracting considerable interest since they show oxygen ion conductivities higher than that of yttria-stabilized zirconia (YSZ) at moderate temperature. Based on the hydrothermal synthesis we presented a simple one step process for the direct preparation of the pure and the high crystalline nanosized rare earth silicates with the structure of apatite under a mild condition (230°C). Since the preparation of the high crystalline silicon based rare earth apatites is performed at high temperature previously and accompanied by subsequent process of grinding, results of this work provide a promising alternative of the existing methodology. Furthermore, due to the relatively low temperature of the preparation of these materials, high doping of monovalent cation can be done, which was not achieved before. [ABSTRACT FROM AUTHOR]

In "Origin of Magnetotransport Properties in APCVD Deposited Tin Oxide Thin Films" by Jurai'c et al., the structural and magnetotransport studies of tin oxide thin films prepared by the cost-effective Atmospheric Pressure Chemical Vapor Deposition method deposited on soda-lime glass substrates [[4]]. The last two decades have witnessed the development of new technologies for thin-film deposition and coating. The Special Issue also includes liquid-phase coatings like sol-gel [[5]], solution immersion [[6]], micro-arc oxidation [[7]], Plasma Electrolytic Oxidation Processing [[8]], and single pulse anodization [[9]] where the authors were more focused on the coating of aluminum. [Extracted from the article]

The crystal quality and surface states are two major factors that determine optical properties of ZnO nanoparticles (NPs) synthesized through nonaqueous sol–gel routes, and both are strongly dependent on the growth conditions. In this work, we investigate the influence of the different growth temperatures (240 and 300 °C) on the morphology, structural and crystal properties of ZnO NP. The effects of conjoining ZnO NP with carbon nanotubes (CNT) and the role of surface states in such a hybrid nanostructure are studied by optical emission and absorption spectroscopy. We demonstrate that depending on the synthesis conditions, activation or passivation of certain surface states may occur. Next, silver nanoparticles are incorporated into ZnO–CNT nanostructures to explore the plasmon–exciton coupling effect. The observed enhanced excitonic and suppressed defect-related emissions along with blue-shifted optical band gap suggest an intricate interaction of Burstein–Moss, surface plasmon resonance and surface band-bending effects behind the optical phenomena in hybrid ZnO–CNT–Ag nanocomposites. [ABSTRACT FROM AUTHOR]

This review addresses the most recent advances in the synthesis approaches, fundamental properties and photocatalytic activity of Cu3N nanostructures. Herein, the effect of synthesis conditions, such as solvent, temperature, time and precursor on the precipitation of Cu3N and the formation of secondary phases of Cu and Cu2O are surveyed, with emphasis on shape and size control. Furthermore, Cu3N nanostructures possess excellent optical properties, including a narrow bandgap in the range of 0.2 eV–2 eV for visible light absorption. In that regard, understanding the effect of the electronic structure on the bandgap and on the optical properties of Cu3N is therefore of interest. In fact, the density of states in the d-band of Cu has an influence on the band gap of Cu3N. Moreover, the potential of Cu3N nanomaterials for photocatalytic dye-degradation originates from the presence of active sites, i.e., Cu and N vacancies on the surface of the nanoparticles. Plasmonic nanoparticles tend to enhance the efficiency of photocatalytic dye degradation of Cu3N. Nevertheless, combining them with other potent photocatalysts, such as TiO2 and MoS2, augments the efficiency to 99%. Finally, the review concludes with perspectives and future research opportunities for Cu3N-based nanostructures. [ABSTRACT FROM AUTHOR]

Abstract: The Zn4Sb3 system is promising for thermoelectric applications due to its very low thermal conductivity coupled with a good power factor. Molecular dynamics calculations based on density functional theory were carried out for different stoichiometries of Zn4Sb3, corresponding to three situations: the composition Zn3.6Sb3 (actually Zn6Sb5 with only one Zn site occupied), a slightly higher Zn content Zn3.8Sb3 (with some of the Zn atoms in interstitial sites), and a slightly lower Zn content Zn3.4Sb3 (with some Zn vacancies). The diffusivity was calculated for different temperatures and the diffusion coefficient plotted in Arrhenius plots. The results compare well with experimental data, and point to a highly mobile Zn species with a very high diffusion coefficient prefactor. [Copyright &y& Elsevier]

Antimicrobial resistance is a menace to public health on a global scale. In this regard, nanomaterials exhibiting antimicrobial properties represent a promising solution. Both metal and metal oxide nanomaterials are suitable candidates, even though their mechanisms of action vary. Multiple antimicrobial mechanisms can occur simultaneously or independently; this includes either direct contact with the pathogens, nanomaterial uptake, oxidative stress, ion release, or any of their combinations. However, due to their specific properties and more particularly fast settling, existing methods to study the antimicrobial properties of nanoparticles have not been specifically adapted in some cases. The development of methodologies that can assess the antimicrobial properties of metallic nanomaterials accurately is necessary. A cost-effective methodology with a straightforward set-up that enables the easy and quick assessment of the antimicrobial properties of metal nanoparticles with high accuracy has been developed. The methodology is also capable of confirming whether the killing mechanism involves ionic diffusion. Finally, Aloe Vera gel showed good properties for use as a medium for the development of antimicrobial ointment. [ABSTRACT FROM AUTHOR]

Potentially, group-Ib elements (Cu, Ag, and Au) incorporated on Zn sites can be used for p-type doping of ZnO, and in the present paper, we use ion implantation to introduce Ag atoms in wurtzite ZnO single crystals. Monitoring the Li behavior, being a residual impurity in the crystals, as a tracer, we demonstrate that Zn interstitials assist the Ag diffusion and lead to Ag pile-up behind the implanted region after annealing above 800 °C. At even higher temperatures, a pronounced Ag loss from the sample surface occurs and concurrently the Ag atoms exhibit a trap-limited diffusion into the crystal bulk with an activation energy of ∼2.6 eV. The dominant traps are most likely Zn vacancies and substitutional Li atoms, yielding substitutional Ag atoms. In addition, formation of an anomalous multipeak Ag distribution in the implanted near-surface region after annealing can be attributed to local implantation-induced stoichiometry disturbances leading to trapping of the Ag atoms by O and Zn vacancies in the vicinity of the surface and in the end-of-range region, respectively. [ABSTRACT FROM AUTHOR]

Highlights from the article: The simultaneous population explosion and the growing lack of clean water today requires disruptively innovative solutions in water remediation. The main asset of nanomaterials is their highly specific surfaces due to their size reduction, which in turn promotes enhanced catalytic activity, subsequently bringing about a more efficient degradation of dyes and organic pollutants. These nanomaterials have been applied to the degradation of dyes and pharmaceuticals, along with heavy metal ion and radioactive ion extraction. Metal oxide nanoparticles have also been presented in this compilation for the degradation of organic species, dyes, and pharmaceuticals.

Cesium is a radioactive fission product generated in nuclear power plants and is disposed of as liquid waste. The recent catastrophe at the Fukushima Daiichi nuclear plant in Japan has increased the 137Cs and 134Cs concentrations in air, soil and water to lethal levels. 137Cs has a half-life of 30.4 years, while the half-life of 134Cs is around two years, therefore the formers' detrimental effects linger for a longer period. In addition, cesium is easily transported through water bodies making water contamination an urgent issue to address. Presently, efficient water remediation methods towards the extraction of 137Cs are being studied. Prussian blue (PB) and its analogs have shown very high efficiencies in the capture of 137Cs+ ions. In addition, combining them with magnetic nanoparticles such as Fe3O4 allows their recovery via magnetic extraction once exhausted. Graphene and carbon nanotubes (CNT) are the new generation carbon allotropes that possess high specific surface areas. Moreover, the possibility to functionalize them with organic or inorganic materials opens new avenues in water treatment. The combination of PB-CNT/Graphene has shown enhanced 137Cs+ extraction and their possible applications as membranes can be envisaged. This review will survey these nanocomposites, their efficiency in 137Cs+ extraction, their possible toxicity, and prospects in large-scale water remediation and succinctly survey other new developments in 137Cs+ extraction. [ABSTRACT FROM AUTHOR]

ZnO is an effective photocatalyst applied to the degradation of organic dyes in aqueous media. In this study, the UV-light and sunlight-driven photocatalytic activities of ZnO nanoparticles are evaluated. A handheld Lovibond photometer was purposefully calibrated in order to monitor the dye removal in outdoor conditions. The effect of ZnO defect states, i.e., the presence of zinc and oxygen defects on the photocatalytic activity was probed for two types of dyes: fuchsin and methylene blue. Three morphologies of ZnO nanoparticles were deliberately selected, i.e., spherical, facetted and a mix of spherical and facetted, ascertained via transmission electron microscopy. Aqueous and non-aqueous sol-gel routes were applied to their synthesis in order to tailor their size, morphology and defect states. Raman spectroscopy demonstrated that the spherical nanoparticles contained a high amount of oxygen vacancies and zinc interstitials. Photoluminescence spectroscopy revealed that the facetted nanoparticles harbored zinc vacancies in addition to oxygen vacancies. A mechanism for dye degradation based on the possible surface defects in facetted nanoparticles is proposed in this work. The reusability of these nanoparticles for five cycles of dye degradation was also analyzed. More specifically, facetted ZnO nanoparticles tend to exhibit higher efficiencies and reusability than spherical nanoparticles. [ABSTRACT FROM AUTHOR]

Sunlight-driven photocatalytic degradation is an effective and eco-friendly technology for the removal of organic pollutants from contaminated water. Herein, we describe the one-step synthesis of Cu-Cu2O-Cu3N nanoparticle mixtures using a novel non-aqueous, sol-gel route and their application in the solar-driven photocatalytic degradation of methylene blue. The crystalline structure and morphology were investigated with XRD, SEM and TEM. The optical properties of the as-prepared photocatalysts were investigated with Raman, FTIR, UV-Vis and photoluminescence spectroscopies. The influence of the phase proportions of Cu, Cu2O and Cu3N in the nanoparticle mixtures on the photocatalytic activity was also investigated. Overall, the sample containing the highest quantity of Cu3N exhibits the highest photocatalytic degradation efficiency (95%). This enhancement is attributed to factors such as absorption range broadening, increased specific surface of the photocatalysts and the downward band bending in the p-type semiconductors, i.e., Cu3N and Cu2O. Two different catalytic dosages were studied, i.e., 5 mg and 10 mg. The higher catalytic dosage exhibited lower photocatalytic degradation efficiency owing to the increase in the turbidity of the solution. [ABSTRACT FROM AUTHOR]

We report on the synthesis of ZnO nanoparticles and their hybrids consisting of carbon nanotubes (CNT) and polystyrene sulfonate (PEDOT:PSS). A non-aqueous sol–gel route along with hydrated and anhydrous acetate precursors were selected for their syntheses. Transmission electron microscopy (TEM) studies revealed their spherical shape with an average size of 5 nm. TEM also confirmed the successful synthesis of ZnO-CNT and ZnO-PEDOT:PSS hybrid nanocomposites. In fact, the choice of precursors has a direct influence on the chemical and optical properties of the ZnO-based nanomaterials. The ZnO nanoparticles prepared with anhydrous acetate precursor contained a high amount of oxygen vacancies, which tend to degrade the polymer macromolecule, as confirmed from X-ray photoelectron spectroscopy and Raman spectroscopy. Furthermore, a relative increase in hydroxyl functional groups in the ZnO-CNT samples was observed. These functional groups were instrumental in the successful decoration of CNT and in producing the defect-related photoluminescence emission in ZnO-CNT. [ABSTRACT FROM AUTHOR]

In this work we show that atomic layer deposition (ALD) stands out as a very promising method for coating nanomaterials and, more specifically, nanoporous materials of technological interest in heterogeneous catalysis. ALD is capable of coating extremely complex shapes with high conformality and high aspect ratios. The current work describes deposition of ZnO and CoO thin films on γ-alumina nanoporous particles with sizes ranging from 20 to 100 µm in diameter, as well on aluminum membrane discs (anodiscs), and converting the surfaces into nanoporous, mechanically more robust spinel phases. We maintain the porosity of the supporting γ-alumina particle, despite the addition of material to the 16 nm pores, by utilizing subsequent reactions between the coated layer and γ-alumina, following the Kirkendall mechanism. The oxide thin film coatings are deposited at 175 and 167°C for ZnO and cobalt oxide, respectively, and thereafter annealed at from 600 to 1000°C for 3 h. This represents a new way to produce highly porous spinel particles and spinel-coated membrane discs. [ABSTRACT FROM AUTHOR]

Abstract: We report on a one-step hydrothermal growth of one-dimensional (1D) WO3 nanostructures, using urea as 1D growth-directing agent and a precursor free of metals other than tungsten. By decreasing the pH of the starting solution, the size of the nanostructures was reduced significantly, this development being accompanied by the realization of phase pure hexagonal WO3 nanorods (elimination of monoclinic impurity phase) and a red shift in optical absorption edge. Surface analyses indicated the presence of reduced tungsten species in the WO3 nanostructures, which increased two-fold in a hydrated WO3 phase obtained with further decrease in pH. We suggest that oxygen vacancies are responsible for this defect state in WO3, while protons are responsible or contribute significantly to the same in the hydrated phase. [Copyright &y& Elsevier]

Abstract Carbide-derived carbons (CDC) are porous carbon materials with tunable pore structure, very high specific surface area and of great potential for electrochemical applications. In this work CDC-supported transition metal macrocyclic electrocatalysts are prepared using two different type of CDC materials and iron phthalocyanine (FePc). Herein, we report the superior electrocatalytic properties of FePc/CDC catalysts fabricated via simple pyrolysis approach. The morphology, composition and structural features of these CDC-based non-noble metal catalysts are evaluated using scanning and transmission electron microscopies, X-ray photoelectron spectroscopy, N 2 physisorption and X-ray diffraction analysis. The electrochemical oxygen reduction reaction (ORR) behavior of FePc/CDC catalysts is evaluated employing the rotating disk electrode (RDE) method. FePc modified CDC materials demonstrate a superior ORR electrocatalytic activity in alkaline conditions, showing onset potential of −0.05 V (vs. SCE) close to that of commercial Pt/C. Thus, the RDE results show great potential of these non-Pt catalysts as cathode materials in metal-air batteries and alkaline membrane fuel cells. Graphical abstract Image 1091 Highlights • Carbide-derived carbon (CDC) materials are modified with iron phthalocyanine (FePc). • Two CDC materials with different specific surface area and porosity are used as supports. • FePc/CDC catalysts are characterized by SEM, TEM, XPS, XRD and the BET method. • FePc/CDC catalysts show excellent activity towards the ORR in alkaline conditions. • FePc/CDC materials are promising cathode catalysts for alkaline membrane fuel cells. [ABSTRACT FROM AUTHOR]

Non-precious metal catalysts for electrochemical oxygen reduction reaction are synthesised by pyrolysis of multi-walled carbon nanotubes in the presence of nitrogen and iron precursors. For the physico-chemical characterisation of the catalysts transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction are used. The electrocatalytic activity of the catalysts for oxygen reduction is studied in 0.1 M KOH solution using the rotating disk electrode method. The Fe-containing nitrogen-doped carbon nanotubes exhibit an enhanced electrocatalytic performance as compared to metal-free counterparts and their electrocatalytic activity is comparable to that of commercial Pt/C catalyst. Alkaline direct methanol fuel cell tests also show performance close to Pt/C. Thus, these materials can be considered as promising cathode catalysts for application in alkaline fuel cells. [ABSTRACT FROM AUTHOR]

Iron- and cobalt-containing nitrogen-doped carbon catalysts based on multi-walled carbon nanotubes are prepared using pyrolysis of dicyandiamide and CoCl 2 or FeCl 3 at 800 °C. The electroreduction of oxygen is studied in 0.5 M H 2 SO 4 solution by the rotating disk electrode method and the surface morphology and composition of the catalysts are characterised by scanning and transmission electron microscopies and X-ray photoelectron spectroscopy. The as-prepared catalysts show mediocre electrocatalytic activity for oxygen reduction reaction (ORR), which increases as a result of acid treatment and second pyrolysis. The electrocatalytic activity of Fe-containing catalyst towards the ORR surpasses that of Co-based material and it supports a 4-electron reduction of O 2 . Co-containing catalyst, in turn, shows higher stability. Both catalysts are highly methanol tolerant in acid media. The transition metal-containing N-doped carbon materials are promising cathode catalysts for low-temperature fuel cells. [ABSTRACT FROM AUTHOR]

In this work the electrocatalysis of oxygen reduction on iron and cobalt phthalocyanine modified reduced graphene oxide/multi-walled carbon nanotube (rGO/MWCNT) composite catalyst has been investigated. Modification of the carbon support was achieved by pyrolysing the mixture of rGO/MWCNT in the presence of metallophthalocyanine compounds at 800 °C. The surface morphology, graphitisation and surface composition of the catalyst materials were characterised by transmission electron microscopy (TEM), scanning electron microscopy (SEM), micro-Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The oxygen reduction reaction (ORR) was studied in 0.1 M KOH and 0.5 M H 2 SO 4 solutions on glassy carbon electrodes modified with MN 4 -macrocycle/rGO/MWCNT catalysts employing the rotating disk electrode (RDE) method. The RDE results show that both iron and cobalt phthalocyanine modified rGO/MWCNT electrocatalysts are highly active for ORR in alkaline solution while in acid media these materials exhibit only modest ORR activity. [ABSTRACT FROM AUTHOR]