Noble Materials Research Articles

High Purity Graphene Oxide Using Electrochemical Synthesis and Its Application

AbstractIn order to fabricate a highly efficient super capacitor, a noble material, graphene oxide (GO), is synthesized by simple electrochemical synthesis method. The chosen source material is an ordinary graphite rod extracted from Nippo battery. Raman spectroscopy as well as Fourier transform infrared spectroscopy affirms the formation of highly pure GO. The super capacitor is fabricated with prepared graphene oxide based electrodes and ionic liquid as electrolyte and tissue paper as separator. The prepared cell shows promising results, a high capacitance value of 78.82 F g−1 at 20 mV s−1 scan rate. The prepared cell is also tested after 30 days in order to determine its stability and performance.

Electrochemical valorization of crude glycerol in alkaline medium for energy conversion using Pd, Au and PdAu nanomaterials

Crude glycerol is a byproduct from biodiesel production, and due to overproduction, new applications requiring the minimum purification steps are needed. The electrochemical valorization of crude glycerol is one of the most attractive applications. In this work, the use of crude glycerol as fuel for energy conversion applications was studied on noble materials such as Pd/C, Au/C and PdAu/C nanoparticles with different Pd/Au atomic composition (1:1, 3:1 and 5:1) with the aim of identifying the main barriers to improve the crude glycerol electro–oxidation reaction (crude GOR). High–resolution transmission electron micrographs revealed that Pd and PdAu nanoparticles had average sizes below 10 nm, while Au nanoparticles had particle sizes of 16.2 ± 1.4 nm. Besides, crude glycerol was obtained from a biodiesel prepared by a transesterification reaction assisted by sonication, resulting in a crude glycerol with a high glycerol content (>95 V/V %). The electrocatalytic evaluation indicated that Pd5Au1/C was the material with the highest current density for crude GOR, displaying 140.1 mA mgPdAu−1, which was 1.8, 2.73, 2.79, 4.14 and 2.2 times higher to that obtained for Pd3Au1/C, Pd/C, Au/C, Pd1Au1/C, and commercial Pd/C, respectively. Moreover, this current density was 20% higher to that obtained for analytical grade glycerol, which was attributed to the bimetallic capability of Pd5Au1 to oxidize both, glycerol and methanol presented in crude glycerol. In summary, it was found that the competition between the adsorption of methanol and glycerol on active sites plays a major role on the activity for crude GOR.

Three-dimensional PdCuM (M = Ru, Rh, Ir) Trimetallic Alloy Nanosheets for Enhancing Methanol Oxidation Electrocatalysis.

Owing to their intrinsically high activity and rich active sites on the surface, noble metal materials with an ultrathin two-dimensional nanosheet structure are emerging as ideal catalysts for boosting fuel cell reactions. However, the realization of controllable synthesis of multimetallic Pd-based alloy ultrathin nanosheets (NSs) for achieving enhanced electrocatalysis evolved from compositional and structural advantages remains a grand challenge. Herein, we report a universal method for the construction of a new series of the three-dimensional (3D) multimetallic PdCuM (M = Ru, Rh, Ir) superstructures that consist of ultrathin alloy NSs. Different from the conventional 2D ultrathin nanostructure, the 3D PdCuM NSs that endowed with abundant routes for fast mass transport, high noble material utilization efficiency, and ligand effect from M to PdCu display large promotion in electrocatalytic performance for the methanol oxidation reaction. Impressively, the composition-optimized Pd59Cu33Ru8 NSs, Pd57Cu34Rh9 NSs, and Pd63Cu29Ir8 NSs show the mass activities of 1660.8, 1184.4, and 1554.8 mA mg-1 in alkaline media, which are 4.9, 3.5, and 4.6-fold larger than that of commercial Pd/C, respectively. More importantly, all of the PdCuM NSs are also very stable for long-term electrochemical tests.

Galvanic Corrosion of Automotive Mixed Metal Substrates: Fundamental Understanding

Dissimilar metal joining is of increasing interest in many structural applications due to its potential to enable light weighting. Light-weight substrates such as aluminum alloys, magnesium alloys and carbon-fiber reinforced polymer (CFRP) are increasingly used in place of conventional steels due to their high strength-to-weight ratios. Two of the main challenges associated with the increased usage of mixed metal systems are galvanic corrosion and challenges with classical joining methods. 1,2. Most joining methods such as riveting, mechanical fasteners, and welding, results in electrical connection between the joined metals, which poses galvanic corrosion issues. Even galvanic isolation approaches such as the use of adhesives can cause galvanic corrosion problems due to the complexity of mixed metal assemblies. In galvanic coupling scenarios, the less noble material experiences severe corrosion and more noble material is protected. It is important to build a fundamental understanding of this phenomenon relative to the metallurgy and electrochemistry of the substrates, as well as the coupling method, to provide effective corrosion mitigation solutions. Electrochemical test techniques such as zero resistance ammeter measurements, open circuit potential measurements, and potentiodynamic polarization were utilized to understand effect of substrate type and solution pH on galvanic corrosion. In addition to the substrate effect, the effect of fastener type on galvanic corrosion between substrate and fasteners was also investigated for selected systems. The influence of joining methods such as self-piercing rivets, adhesives, and mechanical fasteners on galvanic corrosion was also studied. Galvanic and self-coupled coupons were exposed to standard laboratory accelerated life cycle test methods. Wedging by corrosion products, scribe creep, and corrosion volume loss were each characterized to quantify the extent of galvanic corrosion after environmental testing. Preliminary results indicated that galvanic coupling enhanced the wedging of substrate by corrosion products when aluminum alloy 6111-T4 (AA 6111-T4) is coupled with cold rolled steel (CRS). In addition, the pitting corrosion of AA 6111-T4 increased when it is coupled with CRS (Figure 1). Although hot dip galvanized (HDG) based galvanic coupons showed no significant wedging by corrosion products, galvanic coupling of CRS with HDG aggravate the scribe creep of HDG. Galvanic isolation methods such as coating before joining or utilizing adhesives significantly reduced galvanic corrosion in the model mixed-material systems. Figure 1. Average pit depth of AA 6111-T4 substrate coupled with different mixed-metal substrates after various exposure times in neutral and acidic cyclic corrosion tests (CCT). Acknowledgements: Research was sponsored by the Army Research Laboratory, the Tank Automotive Research Design Engineering Center, and Drexel University under Cooperative Agreement W911NF-13-2-0046 and related sub awards.

Precious Metal Free Materials As Efficient Catalysts for Water Splitting

Precious Metal Free Materials as Efficient Catalysts for Water Splitting Pei Kang Shen*, Zhi Qun Tian Collaborative Innovation Center of Sustainable Energy Materials, Guangxi University100 Daxue Road, Nanning 530004, Guangxi, China*E-mail address: pkshen@gxu.edu.cn Water electrolysis is a promising approach for large-scale and sustainable hydrogen production. However, its kinetics is slow and requires precious metal catalysts to efficiently operate. Therefore, great efforts are being undertaken to design and prepare low-cost and highly efficient catalysts to boost the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Currently, we developed different noble metal free materials as efficient catalysts for HER, OER, and full water splitting. For HER, the catalysts with novel nanostructures were prepared, such as carbon-encapsulated WOx (WOx@C), N-doped porous MoN nanobelts, nitrogen and fluorine dual-doped porous graphene-nanosheets, K0.4TaO2.4F0.6 nanocubes, Ni3S2 nanowires, TiN nanowires, nanoflower-like MoO2, et al. For OER catalysts, the Mo- and Fe-modified Ni(OH)2/NiOOH nanosheets, nitrogen-decorated iron-nickel sulfide nanosheets, Mo-doped NiOOH nanosheets, tantalum dioxyfluoride, pristine carbon nanotubes, graphene supported MnO2 nanowires were studied. For full water splitting, the porous WO2 hexahedral networks, heteroatoms dual doped porous graphene nanosheets, three-dimensional porous MoNi4 networks, porous MoO2 nanosheets, dye functionalized carbon nanotubes were studied. The synthesized materials displayed excellent catalytic activity for hydrogen evolution, oxygen evolution, and full water splitting, and can be applied as low cost and highly active multifunctional catalysts with excellent ORR and OER performance. The improved activity and active origin of aforementioned catalysts are clarified through experimental analysis and DFT calculation. These studies pave the way for the design and development of cheaper, highly efficiently and more durable catalysts for wider applications.

NbO2 as a Noble Zero-Strain Material for Li-Ion Batteries: Electrochemical Redox Behavior in a Nonaqueous Solution

Lithium-ion batteries are widely available commercially and attempts to extend the lifetime of these batteries remain necessary. The energy storage characteristics of NbO2 with a rutile structure as a material for the negative electrode of lithium-ion batteries were investigated. When negative potential was applied to the NbO2 electrode during application of a constant current in a nonaqueous solution containing lithium ions, these ions were inserted into the NbO2. Conversely, upon application of positive potential, the inserted lithium ions were extracted from the NbO2. In situ X-ray diffraction results revealed that the variation in the volume of NbO2 accompanying the insertion and extraction of lithium was 0.14%, suggesting that NbO2 is a zero-strain (usually defined by a volume change ratio of 1% or less) active material for lithium-ion batteries. Moreover, the highly stable structure of NbO2 allows the corresponding electrode to exhibit excellent cycling performance and coulombic efficiency.

Synthesis and characterization of nanostructured molybdenum oxynitride films fabricated by sub-atmospheric chemical vapor deposition

To support the trend of a new green energy introduction in economics it has become urgent nowadays that more available and cheaper materials would substitute noble and/or expensive materials (Au, Ag, Pt, Pd, Ga …). Therefore, we studied molybdenum oxynitride films due to their catalytic properties. Molybdenum oxynitride films were fabricated by sub-atmospheric chemical vapor deposition (SACVD). According to Raman spectroscopy, grown platelets possessed MoO3 structure up to 12 at. % NH3 in NH3/air mixture. With the increasing amount of NH3 in the reaction atmosphere (16–25 at. % NH3), the films became heterogeneous containing Mo4O11 and MoO2 suboxides. Nanostructures – nanorods, nanoribbons - developed gradually at those samples with highest concentrations of NH3 in the atmosphere (25–33 at. % NH3) whose structure was built by blocks of corner-sharing Mo-octaedra separated by double layers of edge-sharing Mo-octaedra, which was revealed by Electron Diffraction Tomography (EDT). X-ray Photoelectron Spectroscopy (XPS), similarly to Raman spectroscopy, showed a gradual rise of molybdenum suboxides with NH3 increase in the atmosphere, which was indicated by the successive appearance of Mo6+ → Mo5+ → Mo4+ species. As N 1s XPS signal was fully overlapped by the Mo 3d5/2 one, a new procedure of a standard selected was used for the estimation of the nitrogen content in the films. This material was capable of reducing water under illumination as found by Cycling Votammetry (CV).

Preparation of cyclonic Co3O4/Au/mesoporous SiO2 catalysts with core–shell structure for solvent-free oxidation of benzyl alcohol

• A core–shell catalyst was prepared by cyclonic Co 3 O 4 as core and m-SiO 2 as shell for selective oxidation of benzyl alcohol. • 58% conversion and 82% selectivity were obtained together with the excellent reusability and stability. • A plausible oxidation reaction mechanism over SiO@Co 3 O 4 /Au@m-SiO 2 catalysts was tentatively proposed. As one of the ideal catalysts, noble metal materials can realize the conversion from benzyl alcohol to benzaldehyde. However, in previous reports, the loss of surface noble metal is one of the important reasons for the decrease in reaction performance. Here, a simple method was reported for stepwise fabrication of SiO 2 @Co 3 O 4 /Au@m-SiO 2 catalysts with core–shell structure. On the one hand, the core–shell structure provided abundant reaction sites for the oxidation of benzyl alcohol to benzaldehyde. On the other hand, the outer layer of m-SiO 2 effectively prevents the loss of Au nanoparticles. In this process, we studied the effects of multiple factors on the target reaction by controlling a single variable. The experimental results show that under the optimal conditions (the catalyst dosage, reaction temperature, reaction time and O 2 flow rate are 40 mg, 160 °C, 6 h, 60 ml/min, respectively), the conversion rate of the target reaction reaches 58% and the selectivity is as high as 82%. In the end, a mechanism was put forward to illustrate the underlying reaction pathway in benzyl alcohol oxidation.

Fe3C nanoparticles-loaded 3D nanoporous N-doped carbon: A highly efficient electrocatalyst for oxygen reduction in alkaline media

High-performance, non-precious metal electrocatalysts have been widely considered among the most prospective candidates to replace Pt-based electrocatalysts for the oxygen reduction reaction (ORR) in fuel cells and metal-air batteries. Herein, we report a synthetic method, involving templating, polymerization and pyrolysis, that produces catalytically active iron carbide (Fe3C) nanoparticles-loaded porous N-doped carbon materials from polyaniline- and Fe(III)-modified mesoporous graphitic carbon nitride (g-C3N4). We also show that the resulting noble metal-free materials exhibit good electrocatalytic activity for ORR, with good onset and half-wave potentials, in O2-saturated alkaline solution. The structure, composition, crystallinity, and electrocatalytic activity of these materials are found to depend on the pyrolysis temperature and the specific components in the precursor. In particular, the material obtained by pyrolysis at 1000 °C, named Fe3C/NC-1000, shows excellent electrocatalytic activity and better performance, in terms of both onset and half-wave potentials, than Pt/C (20 wt% Pt). The material also tolerates the methanol crossover reaction better than Pt/C and shows negligible shift in onset and half-wave potentials to negative values even after use in 3000 cycles of electrocatalysis. This robust, non-noble metal-based carbon material can potentially become a viable alternative to precious metal electrocatalysts for ORR.

Co-Deposition and Characterization of Hydroxyapatite-Chitosan and Hydroxyapatite-Polyvinylacetate Coatings on 304 SS for Biomedical Devices

During the last decades, biomaterials have been deeply studied to perform and improve coatings for biomedical devices. Metallic materials, especially in the orthopedic field, represent the most common material used for different type of devices thanks to their good mechanical properties. Nevertheless, low/medium resistance to corrosion and low osteointegration ability characterizes these materials. To overcome these problems, the use of biocoatings on metals substrate is largely diffused. In fact, biocoatings have a key role to confer biocompatibility properties, to inhibit corrosion and thus improve the lifetime of implanted devices. In this work, the attention was focused on Hydroxyapatite-Chitosan (HA/CS) and Hydroxyapatite-Polyvinylacetate (HA/PVAc) composites, that have been studied as biocoatings for 304 SS based devices. Hydroxyapatite was selected for its osteoconductivity thanks to its chemical structure similar to bones. Furthermore, Chitosan and Polyvinylacetate are largely used yet in medical field (e.g. antibacterial agent or drug deliver) and in this work were used to create a synergic interaction with hydroxyapatite to increase the strength and bioactivity of coating. Biocotings were obtained by galvanic deposition process that does not require an external power supply. It is a spontaneous electrochemical deposition in which materials with different standard electrochemical potential were short-circuited and immersed in an electrolytic solution. Electrons supply for the cathodic reaction in the noblest material comes from oxidation of the less noble material. SEM, EDS, XRD and RAMAN were performed for chemical-physics characterization of biocoatings. Polarization and impedance measurements have been carried out to evaluate corrosion behavior. Besides, in-vitro cytotoxicity assays have been done for the biological features.

Konsep dan Implementasi Pendidikan Akhlak Pesantren Modern : Studi Pada Pondok Pesantren Modern Miftahunnajah Sleman

The Indonesian nation is indeed in a situation that is not good in relation to the declining character of the nation's generation. The existence of formal education institutions which are expected to shape the personality of students as good members of society turns out that they have not been fully able to form a generation that has character and noble character. The emergence of modern boarding schools that combine formal education and boarding school education is expected to bring fresh air in an effort to minimize the adverse effects caused by the swift currents of globalization. This research is a qualitative field research conducted by choosing phenomenology as its approach. Data obtained through observation, documentation and interviews. The analysis was carried out using data reduction techniques, data display, triangulation and conclusion drawing or verification. From this study, information was obtained that the Miftahunnajah Modern Islamic Boarding School had a good concept in santri moral formation. This concept includes at least six important aspects, namely noble moral material whose main source comes from the Qur'an and Hadith, moral education goals, moral formation programs, moral reference material, teacher and student qualifications. Two important points in the process of noble moral education are carried out integrally, namely teaching and habituation. Cognitive aspects are obtained through teaching in the classroom while habituation by directly applying the knowledge gained in the daily activities of the santri.

Fast sulfurization of nickel foam-supported nickel-cobalt carbonate hydroxide nanowire array at room temperature for hydrogen evolution electrocatalysis

Transition metal sulfide is considered as a kind of promising noble metal-free material for hydrogen evolution reaction (HER). However, most of conventional sulfurization methods require high temperature and/or long reaction time. Herein, a sulfurization strategy at room temperature (25 °C) by using Na2S in aqueous solution is applied to sulfurize nickel foam-supported nickel-cobalt carbonate hydroxide nanowire array, during which amorphous sulfide gradually forms on the surface of nanowire and finally replaces the nanowire completely. It is found that the electrode sulfurized for 5 min in which only a thin sulfide layer is formed presents nearly identical catalytic performance for HER with the electrode that is sufficiently sulfurized for 120 min. The electrode sulfurized at 25 °C for 5 min only needs an overpotential of 100 mV to achieve hydrogen evolution current at 10 mA cm−2 in 1 M KOH, and negligible loss of activity is observed after working at a current density of 20 mA cm−2 for 25 h. The interface between carbonate hydroxide and sulfide is considered to play an important role in the catalysis of HER. The observation in this work can provide new insights into the sulfurization process and the role of sulfide in the process of HER.

Facile Synthesis of Monodispersed α-Ni(OH)2 Microspheres Assembled by Ultrathin Nanosheets and Its Performance for Oxygen Evolution Reduction

Electrocatalytic water splitting is an efficient route to generate renewable energy sources, in which the noble metal materials are usually used as electrocatalysts. But the high price and scarcity of these catalysts impede their large-scale applications. Ni-based materials are considered to be the most suitable catalytic materials to substitute these noble metal materials. In this paper, the monodispersed α-Ni(OH)2 microspheres assembled by ultrathin nanosheets were synthesized by a facile solvothermal method. This method was surfactant-free and no any precipitator was used. The as-obtained products were well characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), thermal gravimetric (TG) analysis, and X-ray photoelectron spectroscopy (XPS). The results of N2 adsorption/desorption isotherm indicate that the BET surface area of the products was 169.94 m2g-1, and the pore-size distribution centered at 3.5 nm. Then, the electrochemical properties were evaluated by linear sweep voltammetry (LSV) in 1 M KOH. At a current density of 10 mA cm2, the overpotential for the α-Ni(OH)2-MS is 320mV, and the Tafel slope is 98.7 mV dec-1, indicating its excellent reaction kinetics for an efficient catalyst toward oxygen evolution reaction (OER).

Recent Development of CO2 Electrochemistry from Li-CO2 Batteries to Zn-CO2 Batteries.

Metal-CO2 batteries with CO2 as cathode active species give rise to opportunities to deal with energy and environmental issues simultaneously. This technology is more appealing when CO2 is flexibly reduced to chemicals and fuels driven by surplus electricity because it represents a low-cost and controllable approach to maximized electricity utilization and value-added CO2 utilization. Nonaqueous metal-CO2 batteries exhibited high discharge voltage and capacity with carbon and oxalate as reduction products from CO2 electrochemistry that lacks proton. In contrast, aqueous Zn-CO2 batteries implemented flexible CO2 electrochemistry for more value-added products accompanied by energy storage based on a proton-coupled electron transfer mechanism. In this Account, we have exemplified our recent results in the development of CO2 electrochemistry from nonaqueous Li-CO2 batteries to aqueous Zn-CO2 batteries toward practical value-added CO2 conversion. Aimed at the challengingly limited CO2 electrochemistry and high cost of nonaqueous Li-CO2 batteries, we proposed aqueous Zn-CO2 batteries. Our previous works on nonaqueous Li-CO2 batteries, aqueous Zn-air batteries, and aqueous CO2 reduction electrocatalysts further shed light on battery mechanism, device construction, and electrocatalyst design. For example, bipolar membranes maintain the stability of the basic anolyte and neutral catholyte, as well as the kinetics of ion transport at the same time, forming the device base for aqueous Zn-CO2 batteries. Moreover, in terms of the electrocatalyst catalyzing both discharge and charge reactions on the cathode, the design of multifunctional electrocatalysts is of great importance for not only CO2 electrochemistry but also spontaneous discharge and energy efficiency of aqueous Zn-CO2 batteries. We have explored a series of multifunctional electrocatalyst cathodes, including noble metal, transition metal, and metal-free materials, all of which facilitated CO2 electrochemistry in aqueous Zn-CO2 batteries with value-added carbon-based products. Meanwhile, several operating models for practical complicated situations are presented, such as rechargeable, reversible, dual-model, and solid-state batteries. Zn-CO2 batteries with different models require different design mechanisms for electrocatalyst cathodes. Reversible aqueous Zn-CO2 batteries with HCOOH generation were enabled by electrocatalysts capable of catalyzing the interconversion of CO2 and HCOOH at low overpotentials, rechargeable aqueous Zn-CO2 batteries were allowed by electrocatalysts capable of catalyzing efficient CO2 reduction and O2 evolution, and dual-model aqueous Zn-CO2 batteries were realized by electrocatalysts capable of catalyzing CO2 reduction, water oxidation, and oxygen reduction. Concluding remarks include a summary of recent CO2 electrochemistry in metal-CO2 batteries and a brief discussion of future challenges and opportunities for practical aqueous Zn-CO2 batteries, such as highly reduced products and high production rate.

Advances in nanomaterials for use in photothermal and photodynamic therapeutics (Review).

Nanomaterials play crucial roles in the diagnosis and treatment of diseases. Photothermal and photodynamic therapy, as two minimally invasive therapeutic methods, have promising potential in the diagnosis and prevention of cancer. Recently, many photothermal materials (such as noble metal material, transition metal sulfur oxides, carbon material and upconversion nanomaterial) and photodynamic materials (such as phthalein cyanogen, porphyrins and other dye molecules) have been applied in photothermal therapy (PTT) and photodynamic therapy (PDT). Moreover, as nanomaterials have suitable biocompatibility, these materials have been applied in cancer therapy. In the present review, we summarized the effects of different material types, synthesis methods, material morphologies and surface modifications on the outcomes of cancer therapy. The application of nanomaterials in PTT and PDT was introduced and the advantages and disadvantages of PTT and PDT in the prevention of cancer were discussed. Finally, we discussed the application of nanomaterials in the combination of PTT and PDT in cancer treatment.

Electroless Deposited IrOx Nanoparticles for Ni Foam Functionalization with Low Iridium Loading

Hydrogen is potentially a reliable, affordable and sustainable energy carrier. Unfortunately hydrogen gas must be usually be generated from other compounds: 96% of Hydrogen is still extracted from fossil fuels, such as natural gas, oil and coal. The generation by electrolysis using the solar energy is a promising carbon free approach but it needs to be improved in terms of efficiency and durability to become economically appealing. A crucial factor is represented by the electrode and catalyst materials. The catalysts with highest activity and stability are noble or rare materials. In particular, IrO2 represents the best compromise for an active and stable oxygen evolution reaction catalyst. In order to minimize the amount of rare material, an affordable technique consists in depositing the catalyst on the surface of a less noble metal, such as nickel or steel. The deposition of IrO2 usually requires high temperature (200-1000°C), high purity precursors and complex experimental set up. In this paper we propose the use of electroless deposition through spontaneous galvanic displacement as a promising and simple deposition technique to produce interconnected IrO2 nanoparticles on nickel foam electrodes (figure 1). The deposition process of Ir on Ni has been studied as a function of time, pH and temperature. The formation of the iridium oxide has been achieved by thermal annealing in air. The experimental conditions have been optimized in order to improve the catalytic activity during water splitting measurements in 1M KOH, using a saturated calomel electrode (SCE) as reference and a Pt wire as counter. Scanning Electron Microscopy (SEM) analyses, coupled with X-ray Energy Dispersive Spectroscopy (EDX) and X-Rays Photoelectron Spectroscopy (XPS) show that, under proper deposition conditions, we can overcome the limits of other deposition techniques, achieving a uniform IrO2 coverage throughout the 3D structure of the Ni foam. Such a condition is crucial for the long term stability of the electrodes under constant current stress. The amount of Ir on the Ni foam has been experimentally evaluated, obtaining optimal results with 8 mg cm−2 of noble metal in a 0.16 cm thick electrode. Such a value is more than two orders of magnitude lower than typical values employed in the PEM electrolyzers, therefore making the present approach very promising. Figure 1

Marble Pieces in the Romanesque Portal of Glory of the Santiago de Compostela Cathedral. New Data through a Multi-Analytical Approach

ABSTRACT Probably the most important Romanesque artwork in Spain, the Portal of Glory of Santiago de Compostela is essentially made in granite, the most abundant stone in the NW of Iberia, with the only exception of five marble pieces. Different hypothesis on the origin of these marbles have previously been proposed based on visual assessment or by directly assuming a local source. To shed light on their quarry provenance, a multi-analytical study was performed combining polarized-light optical microscopy, cathodoluminescence microscopy, XRPD, SEM-EDS and stable C and O isotopes. The comparison of the results with the available databases reveals the use of marbles from the Estremoz Anticline (Portugal) in the three exquisitely carved columns strategically placed in the central arcade, whereas the other two pieces are local marbles, illustrating a more complex consumption of this noble material than that initially expected.

Heterogeneous electrocatalysts design for nitrogen reduction reaction under ambient conditions

Ammonia, as an important carbon-free energy carrier and also an important chemical for producing fertilisers, is mainly synthesized by a traditional Haber–Bosch process with high energy consumption and large amounts of greenhouse gas emissions. Recently, electrocatalytic nitrogen reduction reaction (NRR) has attracted worldwide research attentions as a promising route for achieving green and sustainable ammonia synthesis at ambient conditions. Although exciting advances have been made in the NRR field, the development of electrochemical nitrogen-to-ammonia conversion is still challenging because of the low ammonia yield and unsatisfactory Faradaic efficiency mainly deriving from the poor catalytic activity of catalysts. Herein, various catalyst design strategies for increasing the exposed active sites or altering the electronic structure aiming at improving the apparent activity or intrinsic activity are summarized in this review article. On the basis of effective design strategies, a range of recently reported NRR electrocatalysts, including noble metal-based materials, non-noble metal-based materials, single-metal-atom catalysts, and metal-free materials, are summarized, and the mechanisms of tuning the catalytic activity by applying the design strategies are emphasized based on the combination of theoretical calculations and experimental investigations. It is anticipated that the established correlation between physicochemical properties of catalysts and NRR performance can provide guidance for designing heterogeneous NRR electrocatalysts with high activity, good selectivity, and high stability.

Construction of trace silver modified core@shell structured Pt-Ni nanoframe@CeO2 for semihydrogenation of phenylacetylene

The Pt-Ni nanoframe catalysts have attracted great interest owing to their unique electronic structure and excellent catalytic performance. However, the stability of the tenuous edges of nanoframe-structures is dissatisfactory and their universal applications in catalytic market beyond electrocatalytic reactions are yet to be tapped and explored. Herein, we developed a new core@shell structured Pt-Ni nanoframe@CeO2 (Pt-Ni NF@CeO2) composite via etching the Ni from inhomogeneous Pt-Ni rhombic dodecahedra (Pt-Ni RD) by cerium(III) acetate hydrate (Ce(OAc)3). In this path, Pt-Ni RD was used as self-sacrificial template, while the Ce(OAc)3 serves as the provider of the Ce3+ source and OH− for the formation of CeO2 shell, etchant of Pt-Ni RD, and the surface modification agent. By this way, the etching of Pt-Ni RD and the formation of the CeO2 shell are simultaneously proceeded to form the final Pt-Ni NF@CeO2 in one step. The obtained Pt-Ni NF@CeO2 exhibits strong interfacial charge transfer interaction between Pt-Ni NF core and CeO2 shell even without reduction treatment, leading to enhanced catalytic activity in the hydrogenation of phenylacetylene. After introduction of trace silver, the Pt-Ni-Ag4.9 NF@CeO2 achieves remarkable catalytic performance for the selective conversion of phenylacetylene to styrene: high conversion (100%), styrene selectivity (86.5%), and good stability. It reveals that encapsulation noble metal nanoframes into metal oxide to form core@shell structured hybrids will indeed enhance their stability and catalytic properties. Particularly, this work expends the application of noble metal nanoframes materials to hydrogenation reactions.

One-Pot Facile Synthesis of La0.5Sr0.5CoO3/C by Sol-Microwave Method and Its Electrocatalytic Activity for Oxygen Evolution Reaction

The La0.5Sr0.5CoO3/C was synthesized by sol-microwave process, which has globular particle with size range of 15–25 nm and distributed evenly. The electrode prepared with this catalyst has a current density of 141 mA·cm−2 at 0.7 V (vs. Hg/HgO) in an alkaline medium (6 mol·L−1 KOH). La0.5Sr0.5CoO3/C has excellent catalytic performance for oxygen evolution, which is superior to RuO2/C catalyst and can replace noble metal catalytic materials. The polarization curves of oxygen evolution for La0.5Sr0.5CoO3/C electrode and RuO2 (20%)/C electrode are shown. At 0.7 V (vs. Hg/HgO), the oxygen evolution current density is 141 and 135 mA·cm−2, respectively. The results show that perovskite-type oxide La0.5Sr0.5CoO3/C prepared by sol-microwave method has better catalytic performance than RuO2(20%)/C.