Showing papers on "Platinum published in 2014"
TL;DR: This work couple graphitic-carbon nitride with nitrogen-doped graphene to produce a metal-free hybrid catalyst, which shows an unexpected hydrogen evolution reaction activity with comparable overpotential and Tafel slope to some of well-developed metallic catalysts.
Abstract: Electrocatalytic reduction of water to molecular hydrogen via the hydrogen evolution reaction may provide a sustainable energy supply for the future, but its commercial application is hampered by the use of precious platinum catalysts. All alternatives to platinum thus far are based on nonprecious metals, and, to our knowledge, there is no report about a catalyst for electrocatalytic hydrogen evolution beyond metals. Here we couple graphitic-carbon nitride with nitrogen-doped graphene to produce a metal-free hybrid catalyst, which shows an unexpected hydrogen evolution reaction activity with comparable overpotential and Tafel slope to some of well-developed metallic catalysts. Experimental observations in combination with density functional theory calculations reveal that its unusual electrocatalytic properties originate from an intrinsic chemical and electronic coupling that synergistically promotes the proton adsorption and reduction kinetics.
1,774 citations
TL;DR: This work reports a highly active nitrogen-doped, carbon-based, metal-free oxygen reduction reaction electrocatalyst, prepared by a hard-templating synthesis, for which nitrogen-enriched aromatic polymers and colloidal silica are used as precursor and template, respectively, followed by ammonia activation.
Abstract: There is substantial research underway into the development of efficient and stable electrocatalysts as alternatives to platinum for the oxygen reduction reaction. Here, the authors optimize both porosity and surface functionalization of a nitrogen doped carbon material to achieve notable performance.
886 citations
TL;DR: The extraordinarily high activity and stability of this catalyst open up avenues to replace platinum in technologies relevant to renewable energies, such as proton exchange membrane (PEM) electrolyzers and solar photoelectrochemical (PEC) water-splitting cells.
Abstract: Introducing sulfur into the surface of molybdenum phosphide (MoP) produces a molybdenum phosphosulfide (MoP|S) catalyst with superb activity and stability for the hydrogen evolution reaction (HER) in acidic environments. The MoP|S catalyst reported herein exhibits one of the highest HER activities of any non-noble-metal electrocatalyst investigated in strong acid, while remaining perfectly stable in accelerated durability testing. Whereas mixed-metal alloy catalysts are well-known, MoP|S represents a more uncommon mixed-anion catalyst where synergistic effects between sulfur and phosphorus produce a high-surface-area electrode that is more active than those based on either the pure sulfide or the pure phosphide. The extraordinarily high activity and stability of this catalyst open up avenues to replace platinum in technologies relevant to renewable energies, such as proton exchange membrane (PEM) electrolyzers and solar photoelectrochemical (PEC) water-splitting cells.
876 citations
TL;DR: FeOx-supported platinum single-atom and pseudo-single-atom structures are reported as highly active, chemoselective and reusable catalysts for hydrogenation of a variety of substituted nitroarenes.
Abstract: The catalytic hydrogenation of nitroarenes is an environmentally benign technology for the production of anilines, which are key intermediates for manufacturing agrochemicals, pharmaceuticals and dyes. Most of the precious metal catalysts, however, suffer from low chemoselectivity when one or more reducible groups are present in a nitroarene molecule. Herein we report FeOx-supported platinum single-atom and pseudo-single-atom structures as highly active, chemoselective and reusable catalysts for hydrogenation of a variety of substituted nitroarenes. For hydrogenation of 3-nitrostyrene, the catalyst yields a TOF of ~1,500 h(-1), 20-fold higher than the best result reported in literature, and a selectivity to 3-aminostyrene close to 99%, the best ever achieved over platinum group metals. The superior performance can be attributed to the presence of positively charged platinum centres and the absence of Pt-Pt metallic bonding, both of which favour the preferential adsorption of nitro groups.
839 citations
TL;DR: In this article, four phases of molybdenum carbide were synthesized and investigated for their electrocatalytic activity and stability for hydrogen evolution reaction in acidic solution.
Abstract: Molybdenum carbide has been proposed as a possible alternative to platinum for catalyzing the hydrogen evolution reaction (HER). Previous studies were limited to only one phase, β-Mo2C with an Fe2N structure. Here, four phases of Mo-C were synthesized and investigated for their electrocatalytic activity and stability for HER in acidic solution. All four phases were synthesized from a unique amine-metal oxide composite material including γ-MoC with a WC type structure which was stabilized for the first time as a phase pure nanomaterial. X-ray photoelectron spectroscopy (XPS) and valence band studies were also used for the first time on γ-MoC. γ-MoC exhibits the second highest HER activity among all four phases of molybdenum carbide, and is exceedingly stable in acidic solution.
746 citations
TL;DR: The addition of alkali ions (sodium or potassium) to gold on KLTL-zeolite and mesoporous MCM-41 silica stabilizes mononuclear gold in Au-O(OH)x-(Na or K) ensembles and paves the way for using earth-abundant supports to disperse and stabilize precious metal atoms with alkali additives for the WGS and potentially other fuel-processing reactions.
Abstract: We report that the addition of alkali ions (sodium or potassium) to gold on KLTL-zeolite and mesoporous MCM-41 silica stabilizes mononuclear gold in Au-O(OH)x-(Na or K) ensembles. This single-site gold species is active for the low-temperature (<200°C) water-gas shift (WGS) reaction. Unexpectedly, gold is thus similar to platinum in creating -O linkages with more than eight alkali ions and establishing an active site on various supports. The intrinsic activity of the single-site gold species is the same on irreducible supports as on reducible ceria, iron oxide, and titania supports, apparently all sharing a common, similarly structured gold active site. This finding paves the way for using earth-abundant supports to disperse and stabilize precious metal atoms with alkali additives for the WGS and potentially other fuel-processing reactions.
513 citations
TL;DR: In this article, an overview of the application of Ir and Ir-containing catalysts for the oxygen reduction reaction (ORR) in proton-exchange membrane water electrolyzer anodes, for both OER and ORR in unit regenerative fuel cell oxygen electrodes is presented.
Abstract: Among noble metal electrocatalysts, only iridium presents high activity for both the oxygen reduction reaction (ORR) in acid medium, in the oxide form, and the oxygen evolution reaction (OER) in acid medium, alloyed with first row transition metals. Indeed, platinum, the best catalyst for the ORR, has poor activity for the OER in any form, and ruthenium, the best catalyst for the OER, in the oxide form, possess poor activity for the ORR in any form. In this work, an overview of the application of Ir and Ir-containing catalysts for the OER in proton-exchange membrane water electrolyzer anodes, for the ORR in proton exchange membrane fuel cell cathodes, and for both OER and ORR in unit regenerative fuel cell oxygen electrodes is presented.
452 citations
TL;DR: Some most recent progresses on Pt(IV) prodrugs which can be activated once enter tumor cells, polynuclear Pt(II) complexes which have unique DNA binding ability and mode, anti-metastatic Ru(II)/Ru( III) complexes, and Au(I)/Au(III) and Ti( IV) antitumor active complexes are described.
407 citations
TL;DR: It is demonstrated that nickel phosphide (Ni12P5) nanoparticles have efficient and stable catalytic activity for the hydrogen evolution reaction and the power conversion efficiency of the resulting composite is larger than that of silicon nanowires decorated with platinum particles.
Abstract: The exploitation of a low-cost catalyst is desirable for hydrogen generation from electrolysis or photoelectrolysis. In this study we have demonstrated that nickel phosphide (Ni12P5) nanoparticles have efficient and stable catalytic activity for the hydrogen evolution reaction. The catalytic performance of Ni12P5 nanoparticles is favorably comparable to those of recently reported efficient nonprecious catalysts. The optimal overpotential required for 20 mA/cm(2) current density is 143 ± 3 mV in acidic solution (H2SO4, 0.5 M). The catalytic activity of Ni12P5 is likely to be correlated with the charged natures of Ni and P. Ni12P5 nanoparticles were introduced to silicon nanowires, and the power conversion efficiency of the resulting composite is larger than that of silicon nanowires decorated with platinum particles. This result demonstrates the promising application potential of metal phosphide in photoelectrochemical hydrogen generation.
393 citations
TL;DR: Under UV illumination in both acidic and neutral-pH solutions, FeP nanoparticles deposited on TiO2 produced H2 at rates and amounts that begin to approach those of Pt/TiO2, therefore FeP is a highly Earth-abundant material for efficiently facilitating the HER both electrocatalytic and photocatalytically.
Abstract: Nanostructured transition-metal phosphides have recently emerged as Earth-abundant alternatives to platinum for catalyzing the hydrogen-evolution reaction (HER), which is central to several clean energy technologies because it produces molecular hydrogen through the electrochemical reduction of water. Iron-based catalysts are very attractive targets because iron is the most abundant and least expensive transition metal. We report herein that iron phosphide (FeP), synthesized as nanoparticles having a uniform, hollow morphology, exhibits among the highest HER activities reported to date in both acidic and neutral-pH aqueous solutions. As an electrocatalyst operating at a current density of −10 mA cm–2, FeP nanoparticles deposited at a mass loading of ∼1 mg cm–2 on Ti substrates exhibited overpotentials of −50 mV in 0.50 M H2SO4 and −102 mV in 1.0 M phosphate buffered saline. The FeP nanoparticles supported sustained hydrogen production with essentially quantitative faradaic yields for extended time periods...
389 citations
TL;DR: G graphene quantum dots, synthesized from inexpensive and earth-abundant anthracite coal, were self-assembled on graphene by hydrothermal treatment to form hybrid nanoplatelets that were then codoped with nitrogen and boron by high-temperature annealing, which makes the resulting materials excellent oxygen reduction electrocatalysts with activity even higher than that of commercial Pt/C in alkaline media.
Abstract: The scarcity and high cost of platinum-based electrocatalysts for the oxygen reduction reaction (ORR) has limited the commercial and scalable use of fuel cells. Heteroatom-doped nanocarbon materials have been demonstrated to be efficient alternative catalysts for ORR. Here, graphene quantum dots, synthesized from inexpensive and earth-abundant anthracite coal, were self-assembled on graphene by hydrothermal treatment to form hybrid nanoplatelets that were then codoped with nitrogen and boron by high-temperature annealing. This hybrid material combined the advantages of both components, such as abundant edges and doping sites, high electrical conductivity, and high surface area, which makes the resulting materials excellent oxygen reduction electrocatalysts with activity even higher than that of commercial Pt/C in alkaline media.
TL;DR: The effects of particle size, inter-particle distance, certain support characteristics and thermal treatment on the catalyst performance and in particular the catalyst stability are evaluated and a set of design criteria for more stable and active Pt/C and Pt-alloy/C materials is suggested.
Abstract: Platinum and Pt alloy nanoparticles supported on carbon are the state of the art electrocatalysts in proton exchange membrane fuel cells. To develop a better understanding on how material design can influence the degradation processes on the nanoscale, three specific Pt/C catalysts with different structural characteristics were investigated in depth: a conventional Pt/Vulcan catalyst with a particle size of 3–4 nm and two Pt@HGS catalysts with different particle size, 1–2 nm and 3–4 nm. Specifically, Pt@HGS corresponds to platinum nanoparticles incorporated and confined within the pore structure of the nanostructured carbon support, i.e., hollow graphitic spheres (HGS). All three materials are characterized by the same platinum loading, so that the differences in their performance can be correlated to the structural characteristics of each material. The comparison of the activity and stability behavior of the three catalysts, as obtained from thin film rotating disk electrode measurements and identical location electron microscopy, is also extended to commercial materials and used as a basis for a discussion of general fuel cell catalyst design principles. Namely, the effects of particle size, inter-particle distance, certain support characteristics and thermal treatment on the catalyst performance and in particular the catalyst stability are evaluated. Based on our results, a set of design criteria for more stable and active Pt/C and Pt-alloy/C materials is suggested.
Book•
14 Mar 2014
TL;DR: In this article, the authors describe a process of C-H bond splitting by low-Valent metal complexes and catalytic Oxidation of Hydrocarbons by molecular oxygen.
Abstract: Preface. Introduction. I. Processes of C-H Bond Activation. II. Hydrocarbon Transformations That Do Not Involve Metals or Their Compounds. III. Heterogeneous Hydrocarbon Reactions with Participation of Solid Metals and Metal Oxides. IV. Activation of C-H Bonds by Low-Valent Metal Complexes (`the Organometallic Chemistry'). V. Hydrocarbon Activation by Metal Ions, Atoms, and Complexes in the Gas Phase and in a Matrix. VI. Mechanisms of C-H Bond Splitting by Low-Valent Metal Complexes. VII. Activation of Hydrocarbons by Platinum Complexes. VIII. Hydrocarbon Reactions with High-Valent Metal Complexes. IX. Homogeneous Catalytic Oxidation of Hydrocarbons by Molecular Oxygen. X. Homogeneous Catalytic Oxidation of Hydrocarbons by Peroxides and Other Oxygen Atom Donors. XI. Oxidation in Living Cells and Its Chemical Models. Conclusion. Abbreviations. Index.
TL;DR: Using DFT calculations, a specific structural element is identified, a ceria "nanopocket", which binds Pt(2+) so strongly that it withstands sintering and bulk diffusion and is therefore identified as an anchoring site for Pt-CeO2 nanocomposites showing high Pt efficiency in fuel-cell catalysis.
Abstract: Platinum is the most versatile element in catalysis, but it is rare and its high price limits large-scale applications, for example in fuel-cell technology. Still, conventional catalysts use only a small fraction of the Pt content, that is, those atoms located at the catalyst's surface. To maximize the noble-metal efficiency, the precious metal should be atomically dispersed and exclusively located within the outermost surface layer of the material. Such atomically dispersed Pt surface species can indeed be prepared with exceptionally high stability. Using DFT calculations we identify a specific structural element, a ceria "nanopocket", which binds Pt(2+) so strongly that it withstands sintering and bulk diffusion. On model catalysts we experimentally confirm the theoretically predicted stability, and on real Pt-CeO2 nanocomposites showing high Pt efficiency in fuel-cell catalysis we also identify these anchoring sites.
TL;DR: In this paper, an electrochemical flow cell system connected to an inductively coupled plasma mass spectrometer (ICP-MS) capable of online quantification of even small traces of dissolved elements in solution is investigated.
Abstract: Platinum is one of the most important electrode materials for continuous electrochemical energy conversion due to its high activity and stability. The resistance of this scarce material towards dissolution is however limited under the harsh operational conditions that can occur in fuel cells or other energy conversion devices. In order to improve the understanding of dissolution of platinum, we therefore investigate this issue with an electrochemical flow cell system connected to an inductively coupled plasma mass spectrometer (ICP-MS) capable of online quantification of even small traces of dissolved elements in solution. The electrochemical data combined with the downstream analytics are used to evaluate the influence of various operational parameters on the dissolution processes in acidic electrolytes at room temperature. Platinum dissolution is a transient process, occurring during both positive- and negative-going sweeps over potentials of ca. 1.1 VRHE and depending strongly on the structure and chemistry of the formed oxide. The amount of anodically dissolved platinum is thereby strongly related to the number of low-coordinated surface sites, whereas cathodic dissolution depends on the amount of oxide formed and the timescale. Thus, a tentative mechanism for Pt dissolution is suggested based on a place exchange of oxygen atoms from surface to sub-surface positions.
TL;DR: It is concluded that the intrinsic activity of the Au-Ox(OH)-S site, where S is a support, is the same for any S, and the support effect is indirect, through its carrying (or binding) capacity for the active sites.
Abstract: For important chemical reactions that are catalyzed by single-site metal centers, such as the water–gas shift (WGS) reaction that converts carbon monoxide and water to hydrogen and carbon dioxide, atomically dispersed supported metal catalysts offer maximum atom efficiency. Researchers have found that for platinum metal supported on ceria and doped ceria in the automobile exhaust catalyst, atomic Pt–Ox–Ce species are the active WGS reaction sites. More recently, preparations of gold at the nanoscale have shown that this relatively “new material” is an active and often more selective catalyst than platinum for a variety of reactions, including the WGS reaction. The activity of gold is typically attributed to a size effect, while the interface of gold with the support has also been reported as important for oxidation reactions, but exactly how this comes about has not been probed satisfactorily. Typical supported metal catalysts prepared by traditional techniques have a heterogeneous population of particles...
TL;DR: Using a variety of characterization techniques, it is shown that the enhanced activity of PtxY over elemental platinum results exclusively from a compressive strain exerted on the platinum surface atoms by the alloy core.
Abstract: Low-temperature fuel cells are limited by the oxygen reduction reaction, and their widespread implementation in automotive vehicles is hindered by the cost of platinum, currently the best-known catalyst for reducing oxygen in terms of both activity and stability. One solution is to decrease the amount of platinum required, for example by alloying, but without detrimentally affecting its properties. The alloy PtxY is known to be active and stable, but its synthesis in nanoparticulate form has proved challenging, which limits its further study. Herein we demonstrate the synthesis, characterization and catalyst testing of model PtxY nanoparticles prepared through the gas-aggregation technique. The catalysts reported here are highly active, with a mass activity of up to 3.05 A mgPt−1 at 0.9 V versus a reversible hydrogen electrode. Using a variety of characterization techniques, we show that the enhanced activity of PtxY over elemental platinum results exclusively from a compressive strain exerted on the platinum surface atoms by the alloy core. The widespread use of fuel cells requires improved catalysts to reduce oxygen efficiently at the cathode. It is shown that model, well-characterized size-selected PtxY nanoparticles can be synthesized by the gas aggregation technique, and that they are highly active for this reaction.
TL;DR: A brief overview of recent progress in the mechanistic studies of FAO, the synthesis of novel Pd- and Pt-based nanocatalysts as well as their practical applications in DFAFCs is provided with a focus on discussing studies significantly contributing to these areas in the past five years.
Abstract: Formic acid as a natural biomass and a CO2 reduction product has attracted considerable interest in renewable energy exploitation, serving as both a promising candidate for chemical hydrogen storage material and a direct fuel for low temperature liquid fed fuel cells In addition to its chemical dehydrogenation, formic acid oxidation (FAO) is a model reaction in the study of electrocatalysis of C1 molecules and the anode reaction in direct formic acid fuel cells (DFAFCs) Thanks to a deeper mechanistic understanding of FAO on Pt and Pd surfaces brought about by recent advances in the fundamental investigations, the “synthesis-by-design” concept has become a mainstream idea to attain high-performance Pt- and Pd-based nanocatalysts As a result, a large number of efficient nanocatalysts have been obtained through different synthesis strategies by tailoring geometric and electronic structures of the two primary catalytic metals In this paper, we provide a brief overview of recent progress in the mechanistic studies of FAO, the synthesis of novel Pd- and Pt-based nanocatalysts as well as their practical applications in DFAFCs with a focus on discussing studies significantly contributing to these areas in the past five years
TL;DR: Efficient deep-blue-emitting tetradentate platinum complexes with a narrow spectral bandwidth are presented, which demonstrate CIEx ≈ 0.15 and CIEy < 0.1.
Abstract: Efficient deep-blue-emitting tetradentate platinum complexes with a narrow spectral bandwidth are presented, which demonstrate CIEx ≈ 0.15 and CIEy < 0.1. Ultimately, an organic light-emitting diode (OLED) with 24.8% peak external quantum efficiency and CIE coordinates of (0.147, 0.079) is fabricated using PtON7-dtb.
TL;DR: IR and X-ray absorption spectra and electron micrographs determine the structures and locations of the platinum complexes in the zeolite pores, demonstrate the platinum-support bonding, and show that the platinum remained site isolated after oxidation and catalysis.
Abstract: A stable site-isolated mononuclear platinum catalyst with a well-defined structure is presented. Platinum complexes supported in zeolite KLTL were synthesized from [Pt(NH3)4](NO3)2, oxidized at 633 K, and used to catalyze CO oxidation. IR and X-ray absorption spectra and electron micrographs determine the structures and locations of the platinum complexes in the zeolite pores, demonstrate the platinum-support bonding, and show that the platinum remained site isolated after oxidation and catalysis.
TL;DR: A novel catalyst material for the selective dehydrogenation of propane is presented and a bifunctional active phase is proposed, in which coordinately unsaturated Ga3+ species are the active species and where Pt functions as a promoter.
Abstract: A novel catalyst material for the selective dehydrogenation of propane is presented. The catalyst consists of 1000 ppm Pt, 3 wt % Ga, and 0.25 wt % K supported on alumina. We observed a synergy between Ga and Pt, resulting in a highly active and stable catalyst. Additionally, we propose a bifunctional active phase, in which coordinately unsaturated Ga3+ species are the active species and where Pt functions as a promoter.
TL;DR: In this article, the authors investigated the dissolution of gold and platinum in 0.1 M HClO4 and 0.05 M NaOH in acid and base electrolytes.
Abstract: Electrochemical dissolution of gold and platinum in 0.1 M HClO4, 0.1 M H2SO4, and 0.05 M NaOH is investigated. The qualitative picture of both metals' dissolution is pH-independent. Oxidation/reduction of the metal's surface leads to the transient dissolution peaks which we label A1 and C1 on the dissolution profiles. Commencement of the oxygen evolution reaction (OER) results in the additional dissolution peak A2. Quantitatively, there are important differences. The amount of gold transiently dissolved in alkaline medium is more than an order of magnitude higher in comparison to that in acidic medium. Oppositely, steady-state gold dissolution in base in the potential region of OER is hindered. The transient dissolution of platinum is by a factor of two higher in base. It is suggested that variation of the pH does not change the mechanism of the OER on platinum. Consequently, the dissolution rate of platinum is equal in acidic and alkaline electrolytes. As an explanation of the observed difference in gold dissolution, a difference in the thickness of compact oxide formed in acid and base is suggested. Growth of a thicker compact oxide in the alkaline medium explains the increased transient and the decreased steady-state dissolution of gold.
TL;DR: A method is presented for the production of metal-terminated TMC nanoparticles in the 1-4 nm range with tunable size, composition, and crystal phase that opens an attractive avenue to replace PGMs in high energy density applications such as fuel cells and electrolyzers.
Abstract: Transition-metal carbides (TMCs) exhibit catalytic activities similar to platinum group metals (PGMs), yet TMCs are orders of magnitude more abundant and less expensive. However, current TMC synthesis methods lead to sintering, support degradation, and surface impurity deposition, ultimately precluding their wide-scale use as catalysts. A method is presented for the production of metal-terminated TMC nanoparticles in the 1–4 nm range with tunable size, composition, and crystal phase. Carbon-supported tungsten carbide (WC) and molybdenum tungsten carbide (MoxW1−xC) nanoparticles are highly active and stable electrocatalysts. Specifically, activities and capacitances about 100-fold higher than commercial WC and within an order of magnitude of platinum-based catalysts are achieved for the hydrogen evolution and methanol electrooxidation reactions. This method opens an attractive avenue to replace PGMs in high energy density applications such as fuel cells and electrolyzers.
TL;DR: In this article, the performance of metal-free nitrogen-doped porous carbon nanosheets (NPCN) with hierarchical porous structure and a high surface area of 1436.02m 2 ǫg −1 for catalyzing ORR was reported.
TL;DR: In this article, the rate-determining role of the bond strength of adsorbed intermediates was verified for the HOR/HER reaction on catalytically most active platinum-based materials relevant to proton exchange membrane fuel cells and electrolyzers.
Abstract: The electrochemical oxidation and evolution of molecular hydrogen are the key reactions at play in the anodes and cathodes of fuel cells and electrolyzers, respectively, which are likely energy conversion and storage devices for renewable energy concepts based on the use of H2 as energy carrier Beyond this practical interest, the hydrogen oxidation and evolution reactions (HOR and HER, respectively) have also played a pivotal role in the historical development of fundamental electrocatalysis theories Indeed, the exponential relation between current and overpotential that describes the kinetics of many electrochemical reactions, viz, the Butler-Volmer equation, was originally validated for the HER, 1 which also became the first electrochemical process for which the rate-determining role of the bond strength of adsorbed intermediates (following Sabatier’s principle) was verified 2 Thus, the HOR/HER has become one of the most extensively studied electrochemical reactions, particularly at low pH values and on the catalytically most active platinum-based materials relevant to proton exchange membrane fuel cells (PEMFCs) and electrolyzers In acid electrolytes, the HOR/HER kinetics on platinum electrodes are extremely fast, so that experimental methods which afford very high mass-transport rates are required in order to unambiguously differentiate kinetic- and diffusion-overpotentials (eg, hydrogen pump experiments in PEMFC 3 or the recently developed floating porous gas diffusion electrode method 4 ) Using the hydrogen-pump approach, the very high exchange current densities (i0 )o f≈200 mA · cmPt2 obtained at 313 K 5 (or ≈600 mA · cmPt2 at 353 K) 3 are consistent with the fact that ultra-low Pt loadings of ≤005 mgPt · cm −2 can be used at the anode of PEMFCs, 3,6 while much higher Pt loadings are required for the cathode electrode due to the much more sluggish oxygen reduction
TL;DR: In this article, a roll-like carbon nitride (C3N4) photocatalyst was synthesized using a supramolecular complex composed of cyanuric acid, melamine, and barbituric acids as the starting monomers.
Abstract: Herein, we report the facile synthesis of an efficient roll-like carbon nitride (C3N4) photocatalyst for hydrogen production using a supramolecular complex composed of cyanuric acid, melamine, and barbituric acid as the starting monomers. Optical and photocatalytic investigations show, along with the known red shift of absorption into the visible region, that the insertion of barbituric acid results in the in situ formation of in-plane heterojuctions, which enhance the charge separation process under illumination. Moreover, platinum as the standard cocatalyst in photocatalysis could be successfully replaced with first row transition metal salts and complexes under retention of 50% of the catalytic activity. Their mode of deposition and interaction with the semiconductor was studied in detail. Utilization of the supramolecular approach opens new opportunities to manipulate the charge transfer process within carbon nitride with respect to the design of a more efficient carbon nitride photocatalyst with cont...
TL;DR: It is found that composition and crystalline structure of the tin element played important roles in the CO2 generation: non-alloyed Pt46-(SnO2)54 core-shell particles demonstrated a strong capability for C-C bond breaking of ethanol than pure Pt and intermetallic Pt/Sn, showing 4.1 times higher CO2 peak partial pressure generated from EOR than commercial Pt/C.
Abstract: Platinum-tin (Pt/Sn) binary nanoparticles are active electrocatalysts for the ethanol oxidation reaction (EOR), but inactive for splitting the C-C bond of ethanol to CO2. Here we studied detailed structure properties of Pt/Sn catalysts for the EOR, especially CO2 generation in situ using a CO2 microelectrode. We found that composition and crystalline structure of the tin element played important roles in the CO2 generation: non-alloyed Pt46-(SnO2)54 core-shell particles demonstrated a strong capability for C-C bond breaking of ethanol than pure Pt and intermetallic Pt/Sn, showing 4.1 times higher CO2 peak partial pressure generated from EOR than commercial Pt/C.
TL;DR: In this article, the one-pot conversion of glycerol to lactic acid using monometallic Au and Pt as well as bimetallic catalysts supported on nanocrystalline CeO2 (n-CeO2) in aqueous solution in the presence of a base and oxygen was investigated.
Abstract: The one pot conversion of glycerol to lactic acid using monometallic Au and Pt as well as bimetallic (Au-Pt) catalysts supported on nanocrystalline CeO2 (n-CeO2) in aqueous solution in the presence of a base and oxygen was investigated. Catalytic performance of the bimetallic catalysts is considerably better than the monometallic ones and is indicative for synergistic effects. The bimetallic system shows excellent activity (TOF=1170h-1 for a batchtime of 20min) with a high selectivity (80%) to lactic acid at 99% glycerol conversion (373K, NaOH to glycerol ratio of 4mol/mol 5bar oxygen). The Au-Pt/nCeO2 catalyst was recycled 5 times in a batch set-up without a significant drop in activity and lactic acid selectivity, indicative for good catalyst stability.
TL;DR: Platinum encapsulated in a dense aluminosilicate matrix with controlled diffusional properties and surface hydroxyl concentrations is used to elucidate the catalytic functions of hydrogen spillover to show distinct chemoselectivity in industrially important hydroconversions.
Abstract: The hydrogen spillover mechanism has been studied for several decades, although its exact elucidation has been hampered by the lack of suitable model catalyst systems. Here, the authors combine experimental and computational techniques to probe the role of surface hydroxyls in the mechanism.
TL;DR: A systematic study on the Pt NP-catalyzed decomposition of hydrogen peroxide and scavenging of superoxide and singlet oxygen over a physiologically relevant pH range of 1.12-10.96 shows that Pt NPs possess peroxidase-like activity of decomposing H2O2 into ˙OH under acidic conditions, but catalase- like activity of producing H2 O and O2 under neutral and alkaline conditions.
Abstract: Recently, platinum (Pt) nanoparticles (NPs) have received increasing attention in the field of catalysis and medicine due to their excellent catalytic activity. To rationally design Pt NPs for these applications, it is crucial to understand the mechanisms underlying their catalytic and biological activities. This article describes a systematic study on the Pt NP-catalyzed decomposition of hydrogen peroxide (H2O2) and scavenging of superoxide (O2˙−) and singlet oxygen (1O2) over a physiologically relevant pH range of 1.12–10.96. We demonstrated that the catalytic activities of Pt NPs can be modulated by the pH value of the environment. Our results suggest that Pt NPs possess peroxidase-like activity of decomposing H2O2 into ˙OH under acidic conditions, but catalase-like activity of producing H2O and O2 under neutral and alkaline conditions. In addition, Pt NPs exhibit significant superoxide dismutase-like activity of scavenging O2˙− under neutral conditions, but not under acidic conditions. The 1O2 scavenging ability of Pt NPs increases with the increase in the pH of the environment. The study will provide useful guidance for designing Pt NPs with desired catalytic and biological properties.