Facile Synthesis of Low-Cost Copper-Silver and Cobalt-Silver Alloy Nanoparticles on Reduced Graphene Oxide as Efficient Electrocatalysts for Oxygen Reduction Reaction in Alkaline Media

Copper-silver and cobalt-silver alloy nanoparticles deposited on reduced graphene oxide (CuAg/rGO and CoAg/rGO) were synthesized and examined as electrocatalysts for oxygen reduction reaction (ORR) and hydrogen peroxide reduction reaction (HPRR) in alkaline media. Characterization of the prepared samples was done by transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction analysis (XRD), and scanning electron microscopy with integrated energy-dispersive X-ray spectroscopy (SEM-EDS). CuAg/rGO and CoAg/rGO nanoparticles diameter ranged from 0.4 to 9.2 nm. The Ag loading was ca. 40 wt.% for both electrocatalysts, with that for Cu and Co being 35 and 17 wt.%, respectively. CoAg/rGO electrocatalyst showed a Tafel slope of 109 mV dec−1, significantly lower than that for CuAg/rGO (184 mV dec−1), suggesting faster ORR kinetics. Additionally, a higher diffusion current density was obtained for CoAg/rGO (−2.63 mA cm−2) than for CuAg/rGO (−1.74 mA cm−2). The average value of the number of electrons transferred during ORR was 2.8 for CuAg/rGO and 3.3 for CoAg/rGO electrocatalyst, further confirming the higher ORR activity of the latter. On the other hand, CuAg/rGO showed higher peak current densities (−3.96 mA cm−2) for HPRR compared to those recorded for CoAg/rGO electrocatalyst (−1.96 mA cm−2)

Efficient methane dry reforming process with low nickel loading for greenhouse gas mitigation

In this study, a series of nickels supported on gamma alumina with a metal dosage ranging from 0.5 to 3 wt.% were prepared and employed as the catalysts. The effect of nickel dosage on material properties, reaction performance, and catalyst deactivation was investigated. At a low dosage, the nickel-free having low metal-support interaction contributed significantly to the total active site. The basicity of the material was enhanced along with the increase in nickel loading. The presence of active metal showed a great impact at the beginning leading to big improvements in feedstock conversion. However, beyond a nickel dosage of 2 wt.%, further additions did not noticeably influence the reaction performance. Regarding catalyst deactivation, different carbon species were observed on catalyst surface, depending on the nickel dosage. Catalysts with less than 2 wt.% nickel exhibited amorphous carbon as the dominant morphology on the spent catalyst. In contrast, catalysts with 2Ni/Al2O3 and 3Ni/Al2O3 compositions showed graphitic carbon as the main side product. These findings provide insights into the relationship between nickel dosage, catalyst properties, and catalytic performance in methane dry reforming. By understanding the effects of nickel loading on material properties and reaction behavior, researchers can optimize catalyst design and develop more efficient and stable catalysts for sustainable syngas production

Carbon dioxide reforming of methane over modified iron-cobalt alumina catalyst : Role of promoter

Cobalt-based catalysts are widely employed in methane dry reforming but tend to deactivate quickly due to coke deposits and metal sintering. To enhance the performance, iron, a cost-effective promoter, is added, improving cobalt's metal dispersibility, reducibility, and basicity on the support. This addition accelerates carbon gasification, effectively inhibiting coke deposition. Methods: A series of iron-doped cobalt alumina MFe-5Co/Al2O3 (M= 0, 0.4, 0.8, 1, 2 wt.%) were prepared via simple incipient-wetness impregnation. The catalysts were thoroughly characterized via modern techniques including BET, XRD, H2-TPR, CO2-TPD. Significant findings: The addition of iron had a minimal impact on the properties of γ-Al2O3, but it significantly affected the dispersibility of cobalt. At an optimal dosage of 0.8 wt.%, there was a notable decrease of 29.44% in Co3O4 particle size. However, excessive iron loading induced agglomeration of Co3O4, which was reversible. The presence of iron also resulted in a decrease in the reduction temperature of Co3O4. The material's basicity was primarily influenced by the loading of iron, reaching its highest value of 705.7 μmol CO2 g−1 in the 2Fe-5Co/Al2O3. The correlation between catalytic activity and the physicochemical properties of the material was established. The 0.8Fe-5Co/Al2O3 sample exhibited excellent performance due to the favorable dispersibility of cobalt, its reducibility, and its affordable basicity

Growth of amorphous, anatase and rutile phase TiO₂ thin films on Pt/TiO₂/SiO₂/Si (SSTOP) substrate for resistive random access memory (ReRAM) device application

Memory structures play a basic role in providing integrated circuits of powerful processing capabilities. Even most powerful processors have nothing to offer without an accompanying memory and importantly, the development of mobile devices is dependent on the continual improvement of memory technology. Herein, we report the synthesis of TiO2 thin films on SSTOP (Pt/TiO2/SiO2/Si) substrate via physical vapour deposition process for the first time. The layers consisted of Si, SiO2, TiO2 and Pt, hence the SSTOP shorthand is used throughout the text. Three different phases of TiO2 thin films were obtained, i.e. amorphous, anatase and rutile phases, by controlling the reaction parameters which were examined by x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), atomic force microscopy (AFM) and Raman-scattering spectroscopy in order to understand the crystallographic, morphological, compositional and scattering properties. The detailed studies confirmed the formation of various crystal phases of titania. The grown thin films on SSTOP substrates were further utilized to fabricate resistive random access memory (ReRAM) devices and the initial electrical screening was performed on capacitor-like structures which were prepared using platinum top electrodes (diameter = 250 μm) on a 14 × 14 array metal contact mask. Current-Voltage (I–V) measurements were implemented employing a range of current compliances (IC). The detailed electrical characterizations revealed that the forming field for a switchable unipolar device was found to be greatest on rutile titania and lowest on the amorphous titania phase. Similarity, the resistive contrast was greatest on the rutile titania phase and lowest on the anatase titania phase

A novel In2O3-doped ZnO decorated mesoporous carbon nanocomposite as a sensitive and selective dopamine electrochemical sensor

Dopamine (DA), a critical biomolecule involved in neurotransmission, is implicated in a variety of neurological disorders. Therefore, accurate detection of DA is crucial for the swift diagnosis of conditions arising from abnormal DA levels. Consequently, we utilized a novel nanocomposite material comprising In2O3-doped ZnO decorated on mesoporous carbon (In2O3·ZnO@MC) as the active nanomaterial for the fabrication of a glassy carbon electrode (GCE). The structural and morphological properties of In2O3·ZnO@MC were comprehensively analyzed utilizing a variety of characterization techniques to confirm its functionality as the sensing nanomaterial. This innovative sensor demonstrates the ability to detect a wide range of DA concentrations, ranging from 0.5 to 2056 μM, in a neutral phosphate buffer solution, exhibiting a high sensitivity of 0.2153 μAμM−1cm−2 and an acceptable detection limit of 0.024 μM. This sensor enables precise DA level measurements in real samples due to its high sensitivity and selectivity. Moreover, it is a dependable and trustworthy sensor for DA measurement due to its outstanding reproducibility, repeatability, and stability

Ionic Liquid-Aided Synthesis of Anatase TiO₂ Nanoparticles: Photocatalytic Water Splitting and Electrochemical Applications

Titanium dioxide nanoparticles play a crucial role in the production of hydrogen gas evolution. Among the four polymorphic phases of TiO2 (anatase, rutile, brookite, and TiO2 (B)), the anatase phase shows good photo activity in catalytic applications. We prepared a single anatasephase of TiO2 nanoparticles usinga facile one-step ionothermal method with the existence of 1-(3,6-dioxa heptane) 3-methyl imidazolium methane sulfonate IL[DOMIMS]. The ionic liquid-based substitution reaction mechanism was utilized for the ionothermal synthesis of TiO2. The anatase phase structure and nanoparticle-like morphology of synthesized TiO2 nanomaterial were confirmed by XRD analysis and TEM studies. The vibrational frequency of the Ti–O–Ti bond at 544 cm−1 was measured usingthe FTIR spectrum, and the UV absorbance of the sample was studied usingthe UV/visible spectra. The prepared TiO2 nanoparticles showed the best results of H2 generation via awater-splitting reaction, liberating 2084 μmol·g−1·h−1 of H2 gas. TiO2 nanoparticles act as a good material for electrochemical applications such as supercapacitors and sensing of dopamine, as well as a better photocatalyst for the degradation of methylene blue

Taguchi L₉ (3⁴) Orthogonal Array Design for Photocatalytic Degradation of Methylene Blue Dye by Green ZnO Particles Biosynthesized by <i>Chrysanthemum</i> spp. Flower Extract

The pollution of synthetic dyes in wastewater exerts many negative impacts on the environment and human health. There is an increasing demand for the degradation of dyes, with an emphasis on photocatalysis. Here, we investigated the bio-mediated synthesis of ZnO using Chrysanthemum spp. flower extract and its utilization for the removal of methylene blue dye under sunlight irradiation. The bandgap energy of green ZnO nanoparticles was determined to be 3.0. The Taguchi L9 (34) orthogonal array design was applied to optimize the photocatalytic degradation of methylene blue dye by green ZnO particles. Four parameters, including the initial concentration (10–50 mg/L), ZnO dosage (0.33–1.0 mg), contact time (30–120 min), and pH (4–10) of the solution, were surveyed based on the Taguchi design. We found that the test result (99.0%) at 10 mg/L was almost equivalent to the predicted value (99.5%) of degradation efficiency. The reaction mechanisms shed light on the major role of reactive oxygen species (•O2−, •OH). More importantly, the green ZnO particles could be reused for at least five cycles and demonstrated high stability

Ionic Liquid-Aided Synthesis of Anatase TiO2 Nanoparticles: Photocatalytic Water Splitting and Electrochemical Applications

Titanium dioxide nanoparticles play a crucial role in the production of hydrogen gas evolution. Among the four polymorphic phases of TiO2 (anatase, rutile, brookite, and TiO2 (B)), the anatase phase shows good photo activity in catalytic applications. We prepared a single anatasephase of TiO2 nanoparticles usinga facile one-step ionothermal method with the existence of 1-(3,6-dioxa heptane) 3-methyl imidazolium methane sulfonate IL[DOMIMS]. The ionic liquid-based substitution reaction mechanism was utilized for the ionothermal synthesis of TiO2. The anatase phase structure and nanoparticle-like morphology of synthesized TiO2 nanomaterial were confirmed by XRD analysis and TEM studies. The vibrational frequency of the Ti&ndash;O&ndash;Ti bond at 544 cm&minus;1 was measured usingthe FTIR spectrum, and the UV absorbance of the sample was studied usingthe UV/visible spectra. The prepared TiO2 nanoparticles showed the best results of H2 generation via awater-splitting reaction, liberating 2084 &mu;mol&middot;g&minus;1&middot;h&minus;1 of H2 gas. TiO2 nanoparticles act as a good material for electrochemical applications such as supercapacitors and sensing of dopamine, as well as a better photocatalyst for the degradation of methylene blue

Si/SiO2/Al2O3 supported growth of CNT forest for the production of La/ZnO/CNT photocatalyst for hydrogen production

The use of ZnO as a photocatalyst with a reduced recombination rate of charge carriers and maximum visible light harvesting remains a challenge for researchers. Herein, we designed and synthesized a unique La/ZnO/CNTs heterojunction system via a sol-gel method to evaluate its photocatalytic performance for hydrogen evolution. A ferrocene powder catalyst was tested for the production of CNT forests over Si/SiO2/Al2O3 substrate. A chemical vapor deposition (CVD) route was followed for the forest growth of CNTs. The La/ZnO/CNTs composite showed improved photocatalytic efficiency towards hydrogen evolution (184.8 mmol/h) in contrast to 10.2 mmol/h of pristine ZnO. The characterization results show that promoted photocatalytic activity over La/ZnO/NTs is attributed to the spatial separation of the charge carriers and extended optical absorption towards the visible light spectrum. The optimum photocatalyst shows a 16 h cycle performance for hydrogen evolution. The H-2 evolution rate under visible light illumination reached 10.2 mmol/h, 145.9 mmol/h and 184.8 mmol/h over ZnO, La/ZnO and La/ZnO/CNTs, respectively. Among the prepared photocatalysts, ZnO showed the lowest H-2 evolution rate due to the fast recombination of electron-hole pairs than heterojunction photocatalysts. This research paves the way for the development of ZnO and CNT-based photocatalysts with a wide optical response and reduced charge carrier recombinations.Web of Science159art. no. 322