In this study, films with compositions of 75 mol.

Hydrogen produced by hydrocarbon reforming typically contains trace amounts of CO, which severely poison anode catalysts in PEMFCs. In this work, Pd was chemically deposited on a support consisting of mesoporous 10 mol% W-doped SnO2 (Sn10W) and graphene nanoplatelets (GNP). Black Pearls 2000 carbon (BP) was subsequently introduced by mechanical mixing to obtain the final Pd/Sn10W-GNP-BP electrode for HOR in acidic media. The surface chemistry investigations by XPS highlighted the presence of Sn2+ and W4+ oxidation states, in addition to Sn4+ and W6+/5+, after Pd deposition, as well as the oxygen bound in residual W=O groups and a highly hydroxylated Pd/Sn10W-GNP surface. SEM showed that Pd nanoparticles were preferentially located on defect-rich oxide regions and at or near the edges of GNP flakes. Electrochemical measurements confirmed HOR activity in acidic media, with BP improving electronic connectivity and Pd utilization. More importantly, Pd/Sn10W-GNP-BP showed remarkable CO tolerance, with CO oxidation starting at ~50 mV and the main oxidation peak at ~415 mV, both markedly lower than for commercial PtRu/C. Based on XPS results correlated with Raman spectroscopy, revealing multivalent W and Sn species, abundant OHads groups, oxygen vacancies and W-related surface defects, a bifunctional mechanism can explain the enhanced CO tolerance.

We approach a cost effective, environmentally friendly, synthesis route of a non-precious electrocatalysts for the anodic oxidation of bioethanol. SnO2 and SnO2-Graphene Nanoplatelets are decorated with nano-crystallized Ni filaments and clusters with peculiar surface chemistry. The electrocatalysts are obtained by subsequently depositing different Ni species by wet impregnation in the presence or absence of a reducing agent (Na borohydride). The effect of the Ni deposition parameters on the crystalline and porous structures, on the surface chemistry and on the electrochemical behavior is highlighted. It is found that the use of a lower temperature (200 degrees C) thermal treatment in the presence of a reducing agent leads to an increase of more than five times of the specific surface area. Electrocatalytic performance is assessed in alkaline medium and, apparently, graphene addition to the SnO2-nickel support allows diminishing the Tafel slope with ca. 20 %, down to 106 mV decade(-1). Such value, that favorably compares to those in the literature, together with the good resistance to fouling that the results of the chronoamperometric and electrochemical impedance spectroscopy (EIS) measurements demonstrate, show that the composites are worthy of development as active materials for biofuel cell applications.

This paper describes the synthesis of cobalt-zinc aluminates (Co1-xZnxAl2O4) pigments, through a simple and ecofriendly method using the aqueous extract of Hibiscus rosa-sinensis leaves. The presence of a pure spinel lattice after calcination at 1000 degrees C for 2 h was confirmed. The mean crystallite size is between 12 and 16 nm. The SEM and TEM investigations revealed a high degree of crystallinity and compositional homogeneity of the prepared nanosized zinc-substituted cobalt aluminates. The average particle size, revealed by TEM, decreases from 48.4 nm to 14.2 nm with the increase of Zn content. The values of the optical energy band gap for the obtained aluminates range from 1.82 to 2.21 eV. The nanoparticles synthesized by this green method could be potentially useful as pigments, the best result being obtained for the Co0.25Zn0.75Al2O4 sample with b* = -6.52 and C* = 12.92 colour coordinates.

Heterogeneous catalysts based on Pt alloys are widely employed in propane dehydrogenation (PDH), yet challenges such as coking and poor nanoparticle stability hinder their broader industrial deployment. Strategies to enhance dispersion and tune the catalyst surface properties remain at the forefront of catalyst design. Here, we demonstrate a new class of PtSn 2 -based catalysts promoted by rare-earth elements for efficient and stable PDH. Among the rare-earth screened, europium (Eu) delivers the most pronounced promotional effect, enabling the formation of ∼1.3 nm PtSn 2 nanoparticles with improved thermal stability. Through its redox flexibility (Eu 3+ /Eu 2+ ), Eu modulates the electronic environment of Pt, tunes surface acidity, and suppresses coke accumulation by directing carbon species away from active sites and onto the support. This work shows that rare-earth elements can serve as multifunctional promoters in alloy catalysts, influencing both structural dispersion and catalytic surface chemistry. The optimized catalyst (0.5% Pt-3% Sn-2% Eu on γ-Al 2 O 3 ) achieves a 40.6% propylene yield at 575 °C and a low deactivation rate (0.047 h −1 ), under conditions relevant to industrial practice. Our findings offer a new strategy for designing high-performance diluted alloy catalysts through rare-earth promotion, applicable to other dehydrogenation and hydrocarbon upgrading reactions where coke suppression and acid–base balance are critical.

Electrochemical water splitting is regarded as a viable solution to future energy demands. Considering this, an innovative method to produce efficient oxygen evolution electrodes based on Co and Ni was proposed and successfully developed, where the metal atoms are intimately mixed before the calcination treatment. Electrochemical measurements demonstrated the high oxygen evolution activity and stability of the thus synthesized electrodes, EDX, and XPS revealing that the surface exhibits a remarkable oxidation resistance, allowing the active phase to better maintain its state when subjected to the aggressive positive potential required for oxygen evolution. Moreover, low electrical resistivity was recorded as a result of reduced thickness of the catalytic layer, further increasing the efficiency. These findings provide new insights into the design of durable and high-performance OER electrodes.

The outstanding properties exhibited by the p-type NiO nanostructures can be greatly affected by morpho-structural and defect characteristics with constructive or competing effects. We have conducted an in-depth study on NiO nanoparticles obtained by hydrothermal synthesis and submitted to various thermal treatments, to monitor the evolution of their structural properties and the effect of the thermal history on their CO sensing. Correlated electron paramagnetic resonance and analytical transmission electron microscopy investigations evidenced an amount of up to 1 % metallic nickel clusters close to surface in the NiO nanoparticles calcined at 400 degrees C and 500 degrees C for 8 h. Subsequent annealing in vacuum and in air of the sample calcined at 400 degrees C resulted in different size distributions and morphology of the NiO nanoparticles and an increase/decrease of the nickel phase, respectively. Comparative CO sensing tests on the two pristine samples and on the sample calcined at 400 degrees C and further annealed in air at 500 degrees C for 2 h showed an increase in the baseline resistance of the later due to the decrease of free charge carriers induced by the dissolution of the nickel clusters. The overall CO sensing results show a strong dependence on the samples thermal history.

S ions are incorporated in the LWO lattice when treated under H 2 S-containing atmospheres. Electronic conductivity increases by the coupled S incorporation and W reduction and, subsequently, H 2 permeation is boosted at moderate temperatures.

The control of catalytic performance using synthesis conditions is one of the main goals of catalytic research. Two series of Pt-Ti/SBA-15 catalysts with different TiO2 percentages (n = 1, 5, 10, 30 wt.%) were obtained from tetrabutylorthotitanate (TBOT) and peroxotitanate (PT), as titania precursors and Pt impregnation. The obtained catalysts were characterized using X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM), N-2 sorption, Raman, X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), hydrogen temperature-programmed reduction (H-2-TPR) and H-2-chemisorption measurements. Raman spectroscopy showed framework titanium species in low TiO2 loading samples. The anatase phase was evidenced for samples with higher titania loading, obtained from TBOT, and a mixture of rutile and anatase for those synthesized by PT. The rutile phase prevails in rich TiO2 catalysts obtained from PT. Variable concentrations of Pt-0 as a result of the stronger interaction of PtO with anatase and the weaker interaction with rutile were depicted using XPS. TiO2 loading and precursors influenced the concentration of Pt species, while the effect on Pt nanoparticles' size and uniform distribution on support was insignificant. The Pt/PtO ratio and their concentration on the surface were the result of strong metal-support interaction, and this influenced catalytic performance in the complete oxidation of methane at a low temperature. The highest conversion was obtained for sample prepared from PT with 30% TiO2.

Herein, a new direct synthesis route leading to a mesoporous NiWO4 with crystalline framework and NiWO4 -graphene nanoplatelets (GNP) composite is reported. Ni and W assembled into a mesoporous tungstate type of symmetry by co-precipitation synthesis route and its composite with GNP were used as supports for electrocatalysts, with reduced Pt content (8 wt.%), in oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR) in acidic medium. A comprehensive assessment of the modifications related to the crystalline and porous structures, morphological aspects as well as the surface chemistry aiming to explain the electrochemical properties was performed. It was found that the presence of GNP during the synthesis process leads, mainly, to the enhanced growth of NiWO4 nanocrystallites, as well as induces changes in the surface chemistry. The elec-trochemical results show that the introduction of GNPs into the NiWO4 composite support leads to a significant improvement in the activity of the Pt electrocatalyst in ORR and HOR compared to both initial NiWO4 and Pt/NiWO4 samples, as well as mechanical mixtures of these catalysts with carbon. Mass activity for hydrogen oxidation, determined in a mixed kinetic-diffusion controlled region, obtained on the 8 wt.% Pt/NiWO4-GNP catalyst was significantly higher compared to the commercial 20 wt.% Pt/C Quintech catalyst. Our comprehensive structural and surface chemistry assessments indicate this composite material as a viable electrocatalyst for PEMFCs using a broader type of fuels.& COPY; 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Hydrothermally formed mesoporous SnO2 was used as a support for nickel chemical deposition and, after subsequent thermal treatment, a high specific surface area (36 m2 g-1) Ni/SnO2 material was obtained. XPS analysis has shown that in the Sn 3d region the spectrum is similar to that of pristine SnO2, whereas Ni species are present on the surface as NiO, Ni2O3 and Ni(OH)2. Mixing Ni/SnO2 with a small amount of Black Pearls (BP) leads to a significant enhancement of the resulting Ni/SnO2-BP composite activity for nitrite anodic oxidation, presumably due to the higher surface area (115 m2 g-1), to better electrical conductivity and to a certain contribution of the BP to an increase in surface density of the active sites. Ni/SnO2-BP also outperforms pristine BP (in terms of Tafel slopes and electron-transfer rates), most likely due to the fact that the Ni(II)/Ni(III) couple can act as an electrocatalyst for nitrite oxidation. A voltammetric method is proposed for the determination of nitrite, over a concentration range of three orders of magnitude (0.05 to 20 mM), with good reproducibility, high stability and excellent sensitivity. The high upper limit of the dynamic range of the analytically useful response might provide a basis for the reliable quantification of nitrite in wastewater.

The present work reports the synthesis of efficient Ti-Au/zeolite Y photocatalysts by different processing of aluminosilicate gel and studies the effect of titania content on the structural, morphological, textural, and optical properties of the materials. The best characteristics of zeolite Y were obtained by aging the synthesis gel in static conditions and mixing the precursors under magnetic stirring. Titania (5, 10, 20%) and gold (1%) species were incorporated in zeolite Y support by the post-synthesis method. The samples were characterized by X-ray diffraction, N-2-physisorption, SEM, Raman, UV-Vis and photoluminescence spectroscopy, XPS, H-2-TPR, and CO2-TPD. The photocatalyst with the lowest TiO2 loading shows only metallic Au on the outermost surface layer, while a higher content favors the formation of additional species such as: cluster type Au, Au1+, and Au3+. A high TiO2 content contributes to increasing the lifetime of photogenerated charge careers, and the adsorption capacity of the pollutant. Therefore, an increase in the photocatalytic performances (evaluated in degradation of amoxicillin in water under UV and visible light) was evidenced with the titania content. The effect is more significant in visible light due to the surface plasmon resonance (SPR) effect of gold interacting with the supported titania.

The effectiveness of mesoporous SnO2 nickel-decoration as a method for obtaining active electrode materials for bioethanol electrochemical oxidation and the way in which the embedment of a small amount of Black Pearls (BP) affects the electrocatalytic performances of Ni/SnO2 systems were investigated. The XPS surface analysis reveals the presence of the Ni2+ /Ni3+ oxidation states in chemical species such as NiO, Ni(OH)2 and Ni2O3. The nickel deposition in a reducing environment does not affect the Sn chemistry and the mesoporosity but significantly increases the SBET. A slight amount of embedded BP improve the SBET value and a small contribution of larger pores appears. Tafel slopes of 80 mV decade-1 were estimated for bioethanol oxidation at Ni/SnO2, which favorably compare to those reported in the literature. It was also found that BP incorporation leads to a decrease of the Tafel slope to 70 mV decade-1, without deleteriously affecting the stability of the electrocatalyst during long-term polarization. EIS results suggested that this improvement might be the combined effect of a lower electrical resistance, a higher specific surface area and a certain contribution from larger pores, which could contribute to a better exposure of the active sites to the bioethanol species.

This article presents a layered mixed oxide thin film composed of Sn, Ti, Zn, and Pr obtained by sol–gel deposition for gas sensing applications. The film was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, UV-Vis spectroscopy, Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), and Electrochemical impedance spectroscopy (EIS). X-ray diffraction results showed the presence of a single crystalline phase with a cassiterite-like structure. Raman spectroscopy revealed characteristic bands of oxygen-deficient SnO2-based nanocrystallites. The band gap energy calculated from UV-Vis spectroscopy is Eg = 3.83 eV. The XPS proved the presence on the surface of all elements introduced by the inorganic precursors as well as their oxidation states. Thus, Sn4+, Ti4+, Zn2+, and Pr3+ were detected on the surface. Moreover, by XPS, we highlighted the presence of OH groups and water adsorbed on the surface. SEM showed the five-layer morphology of the film after five successive depositions. Electrochemical properties were determined by EIS-impedance spectroscopy. The selectivity for gas sensing was also investigated for methane, propane, and formaldehyde and the gas sensing mechanism was explained. The results indicated that the mixed oxide thin film exhibited high sensitivity and selectivity towards specific gases.

The effectiveness of mesoporous SnO 2 nickel-decoration as a method for obtaining active electrode materials for bioethanol electrochemical oxidation and the way in which the embedment of a small amount of Black Pearls (BP) affects the electrocatalytic performances of Ni/SnO 2 systems were investigated. XPS analysis reveals the presence of NiO, Ni(OH) 2 and Ni 2 O 3 chemical species which favors the oxidation of bioethanol and improves the CO x tolerance. Nickel deposition in a reducing environment does not affect the Sn chemistry and the mesoporosity but significantly increases S BET . A slight amount of BP enhances the S BET value and a induces a small contribution of larger pores appears. Tafel slopes of 80 mV decade −1 were estimated for bioethanol oxidation at Ni/SnO 2 , which favorably compare to those reported in the literature. It was also found that BP incorporation leads to a decrease of the Tafel slope to 70 mV decade −1 , without deleteriously affecting the stability of the electrocatalyst during long-term polarization. EIS results suggested that this improvement might be the combined effect of a lower electrical resistance, a higher specific surface area and a certain contribution from larger pores, which could lead to a better access of the bioethanol species to the electrocatalyst surface.

New photocatalysts were obtained by immobilization of titanium and gold species on zeolite Y, hierarchical zeolite Y, MCM-48 and KIT-6 supports with microporous, hierarchical and mesoporous cubic structure. The obtained samples were characterized by X-ray diffraction (XRD), N2-physisorption, scanning and transmission electron microscopy (SEM/TEM), diffuse reflectance UV–Vis spectroscopy (DRUV-Vis), X-ray photoelectron spectroscopy (XPS), Raman and photoluminescence spectroscopy. The photocatalytic properties were evaluated in degradation of amoxicillin (AMX) from water, under UV (254 nm) and visible light (532 nm) irradiation. The higher degradation efficiency and best apparent rate constant were obtained under UV irradiation for Au-TiO2-KIT-6, while in the visible condition for the Au-TiO2-MCM-48 sample containing anatase, rutile and the greatest percent of Au metallic clusters were found (evidenced by XPS). Although significant values of amoxicillin degradation were obtained, total mineralization was not achieved. These results were explained by different reaction mechanisms, in which Au species act as e− trap in UV and e− generator in visible light.

NiO-sensitive materials have been synthesized via the hydrothermal synthesis route and calcined in air at 400 °C and, alternatively, at 500 °C. Structural, morphological, and spectroscopic investigations were involved. As such, the XRD patterns showed a higher crystallinity degree for the NiO calcined at 500 °C. Such an aspect is in line with the XPS data indicating a lower surface hydroxylation relative to NiO calcined at 400 °C. An HRTEM microstructural investigation revealed that the two samples differ essentially at the morphological level, having different sizes of the crystalline nanoparticles, different density of the surface defects, and preferential faceting according to the main crystallographic planes. In order to identify their specific gas-sensing mechanism towards CO exposure under the in-field atmosphere, the simultaneous evaluation of the electrical resistance and contact potential difference was carried out. The results allowed the decoupling of the water physisorption from the chemisorption of the ambient oxygen species. Thus, the specific CO interaction mechanism induced by the calcination temperature of NiO has been highlighted.

Two novel graphene oxide-benzofuran derivatives composites were obtained through the covalent immobilization of [4-hydrazinyl-7nitrobenz-[2,1,3-d]-oxadiazole (NBDH) and respectively, N1-(7-nitrobenzo[c][1,2,5]oxadiazol-4-yl)benzene-1,2-diamine (NBD-PD), on graphene oxide. This covalent functionalization was achieved by activating the carboxylic groups on the surface of graphene oxide by the reaction with thionyl chloride followed by coupling with the amino group of benzofurazane derivatives to obtain the NBD derivatives grafted on graphene oxide. The formation of new materials was check by Raman spectroscopy, fluorescence, infrared spectroscopy and X-ray photoelectron spectroscopy, thermal analysis, scanning electron microscopy, and elemental mapping. The antimicrobial effect of the new composites was evaluated on Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa, both on planktonic and adherent biofilm populations. The cytotoxic effects of the materials on human colon cancer HCT-116 cell line and the normal human fibroblast BJ cell line were evaluated by investigating cell viability and membrane integrity. Apoptosis and colony forming ability of tumor cells were also investigated following exposure to new materials. The biological results of this study have shown that the new materials have potential in combating biofilm formation and also, the tested materials induced cytotoxicity in human colon cancer HCT-116 cell line with limited effects on normal BJ fibroblasts, suggesting their antitumor potential.

This review highlights the recent progress in designing electrocatalysts for producing high performance fuel cells with truly potential applicability to be used in portable devices.

This paper introduces for the first time the preparation of cobalt aluminate (CoAl 2 O 4 ) nanoparticles through a solution combustion method using a Mentha piperita leaves extract. The active constituents present in the mentha leaves extract act as both a chelating and a reducing agent. The isolated precursor was characterized by FTIR, UV–Vis, thermal analysis and XPS. Various techniques (XRD, SEM and TEM, XPS, FTIR and UV–Vis) were also used to characterize the cobalt aluminate spinel from the point of view of structure, morphology and surface chemistry. XRD confirmed the formation of a single-phase, crystalline cubic spinel structure with mean crystalline domain size of 19.5 nm. The TEM analysis showed rhombic and rectangular CoAl 2 O 4 nanoparticles with unimodal particle size distribution and average particle size of about 35 nm. The characteristic peaks of the CoAl 2 O 4 spinel were highlighted by the FTIR spectrum. The tetrahedral configuration of Co 2+ ions in the CoAl 2 O 4 spinel structure was illustrated by the absorbance and XPS spectra. Furthermore, XPS spectra reveal both tetrahedral and octahedral configurations of Al 3+ ions. To evaluate the catalytic properties of the cobalt aluminate, the photocatalytic degradation of methylene blue (MB) was carried out under visible light irradiation.