EtOH Oxidation Research Articles

Activating bulk nickel foam for the electrochemical oxidization of ethanol by anchoring MnO2@Au nanorods

Preparation of MnO2@Au nanorods, which can efficiently activate nickel foam for the electrocatalytic oxidation of ETOH, showing 31% increase in the oxidation current, 28% decrease in Tafel slope, and 40% more reactive sites, is realized.

Detailed mechanism of organic pollutant oxidation via the heterogeneous Fenton reaction requires using at least two substrates, e.g.: DMSO and EtOH

Heterogeneous catalysts hold immense potential applicability in batch-advanced oxidation technologies. The present study examined LaFeO3 Fenton-like catalyzed oxidation of EtOH and DMSO. LaFeO3 is used to catalyze many processes, including an advanced oxidation process (AOP). Less is known about its role in Fenton-like reactions for AOPs. The results point out that two short-lived oxidizing intermediates are formed. Based on oxidation products analysis, it is tentatively proposed that the two short-lived oxidizing intermediates are [((LaFeIIIO3)n)n((LaFeIIIO2(OH)m-2)(LaFeIV(O)O2)2] and [(LaFeIVO3)2(LaFeIIIO3)n-2]2+. Both substrates are oxidized by [((LaFeIIIO3)n)n((LaFeIIIO2(OH)m-2)(LaFeIV(O)O2)2], the oxidation of DMSO by this intermediate is considerably faster than that of ethanol. [(LaFeIVO3)2(LaFeIIIO3)n-2]2+ oxidizes only EtOH. The yield of [((LaFeIIIO3)n)n((LaFeIIIO2(OH)m-2)(LaFeIV(O)O2)2] is larger than that of [(LaFeIVO3)2(LaFeIIIO3)n-2]2+. The knowledge gained in this study will help elucidate the detailed mechanisms of perovskite catalyzed Fenton-like processes and thus facilitate the development of efficient AOPs. The involvement of two short-lived intermediates was shown only by studying the oxidation of two very different substrates, a novel approach whose groundbreaking results are important for catalytic processes that will advance environmental strategies.

Investigating the role of metals loaded on nitrogen-doped carbon-nanotube electrodes in electroenzymatic alcohol dehydrogenation

A new enzymatic biofuel cell (EBFC) is developed using conductive metal alloy nanoparticles with carbon cloth (CC) as an immobilization support for ethanol dehydrogenase (EtDH) and formolase (FLS). Ethanol (EtOH) dehydrogenation to acetaldehyde via direct electron transfer (DET) is pursued as the first step, followed by the condensation of acetaldehyde to acetoin. Metals are deposited onto novel three-dimensional jellyfish (JF)-shaped nanoparticles (SiO2–NCNT–CoFe2), where NCNT denotes “N-doped carbon nanotube”. The fabricated JF–metal–CC–EtDH bioelectrodes exhibit a variation in power generation with varying metals, with a value 37.6-fold higher than that of previously reported EBFC operations with DET for EtOH oxidation. The highest acetoin content is also found in JF-Os–CC–EtDH–FLS, attributable to faster electron uptake by the bioelectrode. First-principles calculations suggest that the d-state delocalization of metal-loaded JF particles is the cause of the enhanced catalytic activity, and it can be utilized in designing electrocatalysts.

Self‐Supporting Bimetallic Pt‐Ni Aerogel as Electrocatalyst for Ethanol Oxidation Reaction

AbstractThe fuel cell has attracted researchers’ attention owing to its advantages of being adjustable and controllable, wide application, high efficiency, and low energy, etc. However, the main cost of fuel cells still comes from catalysts at present. Platinum‐based catalysts are still the most widely used catalysts in both cathodic ORR reactions and anodic EOR reactions. For the anodic EOR process, combined with in‐situ improved self‐gelling and Galvanic Replacement methods, a kind of Pt−Ni aerogel composite with a three‐dimensional porous network structure was prepared. The obtained Pt−Ni bimetallic aerogel materials were characterized by using scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS) and X‐ray diffraction (XRD). Furthermore, the electrocatalytic activity of the synthesized Pt−Ni aerogels for the oxidation of EtOH in KOH was measured. The prepared Pt−Ni aerogel has the characteristics of high conductivity and catalytic activity of metal itself and high specific surface area and porosity of aerogels. The peak current density of Pt−Ni aerogel was about two times of the Ni aerogel prepared under the same situation, and the ECSA of Pt−Ni aerogel was about twice that of Ni aerogel, indicating that the addition of Pt could increase the active site of Pt−Ni aerogel, which made the Pt−Ni aerogel composite material have excellent catalytic activity.

Bimetallic PtPd nanoparticles relying on CoNiO2 and reduced graphene oxide as a most operative electrocatalyst toward ethanol fuel oxidation

Of late, fuel cells have drawn great attentions owing to high-energy demands, fossil fuel depletion and worldwide environmental pollution. Direct ethanol fuel cell (DEFC) constituted as one of the most promising sources of green energy, howbeit the ethanol oxidation reaction (EOR) sluggish kinetic is one of the essential challenges toward the commercialization of DEFCs. Herein, we introduce bimetallic catalyst on CoNiO2 modified reduced graphene oxide (rGO) to completely exploit the advantages of nano-surface structures as well as the reduction of Pt and Pd loading in fuel cells. With the combined advantages of PtPd, CoNiO2 and rGO, a significant enhancement in electrocatalytic behavior, stability and CO poisoning tolerance of PtPd have been observed. Regarding the implications, PtPd/CoNiO2/rGO is greatly preferable than Pt/CoNiO2/rGO and Pd/CoNiO2/rGO in terms of high electroactive surface area (ECSA), electro-catalytic activity, and lower onset potential (Eons) towards the EtOH oxidation in alkaline media. Furthermore, the chronoamperometry curve (CA) illustrated 77% after 3600 s which is dramatically soared compared with the other electrodes (≤40%), demonstrating the high stability of the PtPd bimetallic nanoparticle electrocatalyst. Ultimately, PtPd/CoNiO2/rGO nanocomposite is found to be an excellent anode electrocatalyst for application in DEFCs.

Plasmonic Au–Pd Bimetallic Nanocatalysts for Hot-Carrier-Enhanced Photocatalytic and Electrochemical Ethanol Oxidation

Gold–palladium (Au–Pd) bimetallic nanostructures with engineered plasmon-enhanced activity sustainably drive energy-intensive chemical reactions at low temperatures with solar simulated light. A series of alloy and core–shell Au–Pd nanoparticles (NPs) were prepared to synergistically couple plasmonic (Au) and catalytic (Pd) metals to tailor their optical and catalytic properties. Metal-based catalysts supporting a localized surface plasmon resonance (SPR) can enhance energy-intensive chemical reactions via augmented carrier generation/separation and photothermal conversion. Titania-supported Au–Pd bimetallic (i) alloys and (ii) core–shell NPs initiated the ethanol (EtOH) oxidation reaction under solar-simulated irradiation, with emphasis toward driving carbon–carbon (C–C) bond cleavage at low temperatures. Plasmon-assisted complete oxidation of EtOH to CO2, as well as intermediary acetaldehyde, was examined by monitoring the yield of gaseous products from suspended particle photocatalysis. Photocatalytic, electrochemical, and photoelectrochemical (PEC) results are correlated with Au–Pd composition and homogeneity to maintain SPR-induced charge separation and mitigate the carbon monoxide poisoning effects on Pd. Photogenerated holes drive the photo-oxidation of EtOH primarily on the Au-Pd bimetallic nanocatalysts and photothermal effects improve intermediate desorption from the catalyst surface, providing a method to selectively cleave C–C bonds.

Gold-Palladium Bimetallic Nanoparticles for Inducing Surface Plasmon Resonance to Catalyze Ethanol Oxidation

Gold-palladium (Au-Pd) bimetallic nanoparticles were prepared as a series of alloy and core-shell nanostructures to synergistically couple plasmonic (Au) and catalytic (Pd) metals to tailor the optical and catalytic properties. Catalysts utilizing plasmonic metals that exhibit a localized surface plasmon resonance (SPR) can be harnessed for light-driven enhancement via augmented carrier generation/separation and photothermal conversion. Titania-supported Au-Pd bimetallic nanoparticles were used as catalysts to study the ethanol (EtOH) oxidation reaction, with an emphasis towards driving carbon-carbon (C-C) bond cleavage at low temperatures. Plasmonically-assisted photocatalytic oxidation of EtOH to CO2 under solar simulated-light irradiation was studied by monitoring the yield of gaseous products via suspended particle photocatalysis and electrochemical methods. Results are correlated with Au-Pd composition and homogeneity to maintain SPR-induced charge separation and mitigate the carbon monoxide poisoning effects on Pd. Under solar simulated conditions, carrier generation/separation and photothermal conversion was achieved, resulting in the photogenerated “hot” holes driving the photo-oxidation of EtOH primarily on the AuPd, providing a method to selectively cleave C-C bonds. Bimetallics provide a pathway for driving desired photocatalytic and photoelectrochemical reactions with superior catalytic activity and selectivity.

Different Effects of Knockouts in ALDH2 and ACSS2 on Embryonic Stem Cell Differentiation.

Ethanol (EtOH) is a teratogen that causes severe birth defects, but the mechanisms by which EtOH affects stem cell differentiation are unclear. Our goal here is to examine the effects of EtOH and its metabolites, acetaldehyde (AcH) and acetate, on embryonic stem cell (ESC) differentiation. We designed ESC lines in which aldehyde dehydrogenase (ALDH2, NCBI#11669) and acyl-CoA synthetase short-chain family member 2 (ACSS2, NCBI#60525) were knocked out by CRISPR-Cas9 technology. We selected these genes because of their key roles in EtOH oxidation in order to dissect the effects of EtOH metabolism on differentiation. By using kinetic assays, we confirmed that AcH is primarily oxidized by ALDH2 rather than ALDH1A2. We found increases in mRNAs of differentiation-associated genes (Hoxa1, Cyp26a1, and RARβ2) upon EtOH treatment of WT and Acss2-/- ESCs, but not Aldh2-/- ESCs. The absence of ALDH2 reduced mRNAs of some pluripotency factors (Nanog, Sox2, and Klf4). Treatment of WT ESCs with AcH or 4-hydroxynonenal (4-HNE), another substrate of ALDH2, increased differentiation-associated transcripts compared to levels in untreated cells. mRNAs of genes involved in retinoic acid (RA) synthesis (Stra6 and Rdh10) were also increased by EtOH, AcH, and 4-HNE treatment. Retinoic acid receptor-γ (RARγ) is required for both EtOH- and AcH-mediated increases in Hoxa1 and Stra6, demonstrating the critical role of RA:RARγ signaling in AcH-induced ESC differentiation. ACSS2 knockouts showed no changes in differentiation phenotype, while pluripotency-related transcripts were decreased in ALDH2 knockout ESCs. We demonstrate that AcH increases differentiation-associated mRNAs in ESCs via RARγ.

Surface Plasmon Resonant Gold-Palladium Bimetallic Nanoparticles for Promoting Catalytic Oxidation

AbstractColloidal gold-palladium (Au-Pd) bimetallic nanoparticles were used as catalysts to study the ethanol (EtOH) photo-oxidation cycle, with an emphasis towards driving carbon-carbon (C-C) bond cleavage at low temperatures. Au-Pd bimetallic alloy and core-shell nanoparticles were prepared to synergistically couple a plasmonic absorber (Au) with a catalytic metal (Pd) with composite optical and catalytic properties tailored towards promoting photocatalytic oxidation. Catalysts utilizing metals that exhibit localized surface plasmon resonance (SPR) can be harnessed for light-driven enhancement for small molecule oxidation via augmented photocarrier generation/separation and photothermal conversion. The coupling of Au to Pd in an alloy or core-shell nanostructure maintains SPR-induced charge separation, mitigates the poisoning effects on Pd, and allows for improved EtOH oxidation. The Au-Pd nanoparticles were coupled to semiconducting titanium dioxide photocatalysts to probe their effects on plasmonically-assisted photocatalytic oxidation of EtOH. Complete oxidation of EtOH to CO2 under solar simulated-light irradiation was confirmed by monitoring the yield of gaseous products. Bimetallics provide a pathway for driving desired photocatalytic and photoelectrochemical reactions with superior catalytic activity and selectivity.

Structure-Property-Performance Relationship of Ultrathin Pd-Au Alloy Catalyst Layers for Low-Temperature Ethanol Oxidation in Alkaline Media.

Pd-containing alloys are promising materials for catalysis. Yet, the relationship of the structure-property performance strongly depends on their chemical composition, which is currently not fully resolved. Herein, we present a physical vapor deposition methodology for developing PdxAu1-x alloys with fine control over the chemical composition. We establish direct correlations between the composition and these materials' structural and electronic properties with its catalytic activity in an ethanol (EtOH) oxidation reaction. By combining X-ray diffraction (XRD) and X-ray photelectron spectroscopy (XPS) measurements, we validate that the Pd content within both bulk and surface compositions can be finely controlled in an ultrathin-film regime. Catalytic oxidation of EtOH on the PdxAu1-x electrodes presents the largest forward-sweeping current density for x = 0.73 at ∼135 mA cm-2, with the lowest onset potential and largest peak activity of 639 A gPd-1 observed for x = 0.58. Density functional theory (DFT) calculations and XPS measurements demonstrate that the valence band of the alloys is completely dominated by Pd particularly near the Fermi level, regardless of its chemical composition. Moreover, DFT provides key insights into the PdxAu1-x ligand effect, with relevant chemisorption activity descriptors probed for a large number of surface arrangements. These results demonstrate that alloys can outperform pure metals in catalytic processes, with fine control of the chemical composition being a powerful tuning knob for the electronic properties and, therefore, the catalytic activity of ultrathin PdxAu1-x catalysts. Our high-throughput experimental methodology, in connection with DFT calculations, provides a unique foundation for further materials' discovery, including machine-learning predictions for novel alloys, the development of Pd-alloyed membranes for the purification of reformate gases, binder-free ultrathin electrocatalysts for fuel cells, and room temperature lithography-based development of nanostructures for optically driven processes.

Visible Light-Promoted Plasmon Resonance to Induce “Hot” Hole Transfer and Photothermal Conversion for Catalytic Oxidation

Titanium dioxide (TiO2) semiconductor photocatalysts were photosensitized to the visible spectrum with gold nanospheres (AuNSs) and gold nanorods (AuNRs) to study the ethanol photo-oxidation cycle, with an emphasis toward driving carbon–carbon (C–C) bond cleavage at low temperatures. The photocatalysts exhibited a localized surface plasmon resonance (SPR) that was harnessed to drive the complete photo-oxidation of formic acid (FA) and ethanol (EtOH) via augmented carrier generation/separation and photothermal conversion. Contributions of transverse and longitudinal localized SPR modes were decoupled by irradiating AuNSs–TiO2 and AuNRs–TiO2 with targeted wavelength ranges to probe their effects on plasmonically assisted photocatalytic oxidation of FA and EtOH. Photocatalytic performance was assessed by monitoring the yield of gaseous products during photo-oxidation experiments using a gas chromatography–mass spectrometry–multiple headspace extraction (GC–MS–MHE) analysis method. The complete oxidation of E...

Remarkable enhancement of the selective catalytic reduction of NO at low temperature by collaborative effect of ethanol and NH3 over silver supported catalyst

The NOx selective catalytic reduction (SCR) is extensively studied as an effective process for air pollutants abatement from lean burn and Diesel vehicles. In the implemented Urea-SCR technology, the NO2/NOx ratio is a key parameter that limits the deNOx efficiency at low temperature (175–250°C). We demonstrate that co-feeding of ammonia and ethanol on a Ag/Al2O3 catalyst enables a drastic enhancement of the NOx conversion at temperatures below 200°C using only NO as NOx (standard SCR condition). Even if NO2 is provided at low temperature by the NO oxidation over Ag/Al2O3 in presence of EtOH, the NOx conversion improvement is not only due to a direct reaction between NH3 and NOx, but mainly attributed to the availability of hydrogen H* species resulting from EtOH oxidation (similar to a H2 assisted NH3-SCR process). Due to the presence of remaining NH3 and NO2 (formed over Ag/Al2O3 catalyst), further deNOx efficiency improvement was obtained at low temperature by addition of a NH3-SCR catalyst (WO3/Ce-Zr). The critical dependence of the SCR process on the Diesel Oxidation Catalyst (DOC) efficiency at low temperature is thus avoided.

Facile Route for the Preparation of Ordered Intermetallic Pt3pb-Ptpb Core-Shell Nanoparticles and Its Enhanced Activity for Alkaline Methanol and Ethanol Oxidation

Recently, a new approach that avoids the problems inherent in disordered alloy catalysts has been proposed for highly active electrocatalysts for fuel cell applications [1]. In contrast with disordered alloys, intermetallic compounds with definite compositions and structures, such as PtPb and PtBi, exhibit excellent electrocatalytic performance towards FA oxidation in acidic solutions in terms of onset potential and current density [2]. Abruña et al. have examined the FA, MeOH, and EtOH oxidation activities with a wide range of intermetallic compounds (PtPb, PtBi, and Pt3Ti) in acidic media and found that the intermetallic compounds exhibit enhanced catalytic activity when compared with pure Pt [3]. In our previous study, we reported that PtPb and PtBi ordered intermetallic compounds exhibited higher electrocatalytic activity towards MeOH and EtOH oxidation in alkaline aqueous solutions than Pt, Pt-Ru alloy, and other Pt-based ordered intermetallic compounds [4]. In this paper, we report on the enhancement of the electrocatalytic activity of PtPb ordered intermetallic compounds towards MeOH and EtOH oxidation in alkaline aqueous solutions. To achieve this, carbon black (CB)-supported Pt3Pb(core)-PtPb(shell) intermetallic NPs (Pt3Pb-PtPb NPs/CB) were synthesized via a method (hereafter referred to as the “converting reaction method”) in which the CB-supported Pt NPs react with a Pb precursor in the presence of a reducing agent under microwave irradiation. In the converting reaction method, the Pb atoms were only observed in the PtPb NPs and not on the CB surfaces. In other words, Pb NPs were not formed on CB in the reaction with microwaves, indicating the selective reaction of Pb atoms with Pt NPs on the CB surfaces, as previously reported by Bauer and our group [5]. By controlling the amount of Pb atoms, the core-shell structure with Pt3Pb and PtPb intermetallic phases can be formed in a NP. The activities of Pt3Pb-PtPb NPs/CB were compared with those of the reference samples consisting of pure PtPb NPs/CB and Pt3Pb NPs/CB, which were prepared on the CB through the co-reduction reaction of the Pt and Pb precursors in the presence of a reducing agent and CB (hereafter referred to as the “co-reduction reaction method”). As mentioned above, previously, we have reported that PtPb and PtBi ordered intermetallic phases are the most promising electrocatalysts for MeOH and EtOH oxidations via the exhaustive screening of the ordered intermetallic phases for alkaline MeOH and EtOH oxidations [4]. In this research, our current results obtained with Pt3Pb-PtPb NPs/CB were compared with that of works mentioned above.[1] E.D. Casado-Rivera, J. Volpe, L. Alden, C. Lind, C. Downie, T. Vázquez-Alvarez, A.C.D. Angelo, F.J. DiSalvo, H.D. Abruña, J. Am. Chem. Soc. 126 (2004) 4043-4049.[2] D. Volpe, E.D. Casado-Rivera, L. Alden, C. Lind, K. Hagerdon, C. Downie, C. Korzeniewski, F.J. DiSalvo, H.D. Abruña, J. Electrochem. Soc. 151 (2004) A971-A977[3] F. Matsumoto, C. Roychowdhury, F.J. DiSalvo, H.D. Abruña, J. Electrochem. Soc. 155(2008) B148-B154.[4] F. Matsumoto, Electrochemistry 80 (2012) 132-138.[5] J.C. Bauer, X. Chen, Q. Liu, T.-H. Phan, R.E. Schaak, J. Mater. Chem. 18 (2008) 275-282.

The Enhanced Electrocatalytic Activity over Carbon-Supported Pd-Based Ordered Intermetallic Compounds

In recent years, the direct fuel cells (DFCs) have attracted increasing interest as next energy device in the area of polymer electrolyte membrane fuel cells due to its high efficiency and high power density. Formic acid (FA) has been receiving paramount attention as fuel for DFCs because of its high energy density (1740 Wh kg-1, 2086 Wh L-1) and fuel crossover of FA is smaller than that MeOH [1]. In addition, the electrooxidation current density (and mass activity) of FA over Palladium (Pd) nanoparticles (NPs) is higher than that Platinum (Pt) electrocatalyst [2]. Therefore, the DFCs, which FA is used as fuel, can be operated without Pt electrocatalyst. However, electrocatalytic activity towards electrooxidation of FA is still in need of improvements. In order to enhance electrocatalytic activity towards electrooxidation of FA, Pb was used as secondary material for alloying with Pt because of CO-poisoning tolerance of electrocatalysts. Recently, we have previously reported that ordered intermetallic PtPb efficiently electrochemically catalzed for electrooxidation of FA, MeOH and EtOH [3]. In particular, core shell structure of bimetallic Pt3Pb exhibited efficient electrocatalytic activity for the electrochemical oxidation of FA, MeOH and EtOH. These indicate that Pb atom in ordered intermetallic PtPb (and/or bimetallic Pt3Pb) facilitates more efficiency of FA electrooxidation not only enhancement of electrocatalytic activity but also CO-poisoning tolerance. This study demonstrates the new approach in preparation of carbon supported ordered intermetallic Pd3Pb NPs (Pd3Pb NPs/CB), which has a Cu3Au type structure, via polyol method under air atmospheric air without anneal treatment. In addition, Pb atom in ordered intermetallic Pd3Pb NPs were dissolved under acidic environment by cyclic voltammetry up to 1.1 V, resulting in formed surface-dealloyed Pd-shell ordered intermetallic Pd3Pb core structure (Pd@Pd3Pb NPs/CB). The surface of prepared Pd@Pd3Pb NPs/CB was characterized by using XPS and HR-TEM. The electrochemical activity of prepared Pd@Pd3Pb NPs/CB is compared to commercially available Pt NPs/CB, PtRu NPs/CB and Pd NPs/CB. In addition, electrochemically surface-dealloyed Pd@Pd3Pb NPs/CB has better catalytic activity towards the electrooxidation of FA than other electrocatalysts. [1] Rice, C.; Ha, S.; Masel, R. I.; Wieckowski, A. J. Power Sources 2003, 115, 229. [2] Capon, A.; Parsons, R. J. Electroanal. Chem. 1973, 44, 239. [3] Gunji, T.; Tanabe, T.; Jeevagan, A. J.; Usui, S.; Tsuda, T.; Kaneko, S.; Saravanan, G.; Abe, H.; Matsumoto, F. J. Power Sources 2015, 273, 990.

Redox Potentials of Colloidal n-Type ZnO Nanocrystals: Effects of Confinement, Electron Density, and Fermi-Level Pinning by Aldehyde Hydrogenation.

Electronically doped colloidal semiconductor nanocrystals offer valuable opportunities to probe the new physical and chemical properties imparted by their excess charge carriers. Photodoping is a powerful approach to introducing and controlling free carrier densities within free-standing colloidal semiconductor nanocrystals. Photoreduced (n-type) colloidal ZnO nanocrystals possessing delocalized conduction-band (CB) electrons can be formed by photochemical oxidation of EtOH. Previous studies of this chemistry have demonstrated photochemical electron accumulation, in some cases reaching as many as >100 electrons per ZnO nanocrystal, but in every case examined to date this chemistry maximizes at a well-defined average electron density of ⟨Nmax⟩ ≈ (1.4 ± 0.4) × 10(20) cm(-3). The origins of this maximum have never been identified. Here, we use a solvated redox indicator for in situ determination of reduced ZnO nanocrystal redox potentials. The Fermi levels of various photodoped ZnO nanocrystals possessing on average just one excess CB electron show quantum-confinement effects, as expected, but are >600 meV lower than those of the same ZnO nanocrystals reduced chemically using Cp*2Co, reflecting important differences between their charge-compensating cations. Upon photochemical electron accumulation, the Fermi levels become independent of nanocrystal volume at ⟨N⟩ above ∼2 × 10(19) cm(-3), and maximize at ⟨Nmax⟩ ≈ (1.6 ± 0.3) × 10(20) cm(-3). This maximum is proposed to arise from Fermi-level pinning by the two-electron/two-proton hydrogenation of acetaldehyde, which reverses the EtOH photooxidation reaction.

Pt "Monolayer" Electrocatalysts Revisited: Structure, Lattice Geometry Effects, and Ethanol Oxidation Activity of Pt on Au

Effective utilization of the high energy density of ethanol as a fuel for polymer electrolyte fuel cells is contingent upon complete oxidation of ethanol to carbon dioxide. Major problems associated with the development of electrocatalysts for ethanol oxidation are the high content of Pt and partial oxidation of ethanol to acetaldehyde and acetic acid instead of complete oxidation to carbon dioxide via the 12 electron process. Monolayers of Pt on Au have been proposed and reported1 to be beneficial for EtOH oxidation and possibly for C-C bond splitting. We address this issue with atomic scale microscopy and spectroscopy. In this report, Pt atomic layers supported on both well-defined, extended Au(111) and Au NPs were studied as electrocatalysts for ethanol oxidation reaction (EOR)2. The catalyst were prepared using galvanic displacement methods using Pt(II) and Pt(IV) precursors. Electrochemical testing of these electrocatalysts showed that Au@Pt(II) had substantially higher activity towards EOR than Au@Pt(IV). The atomic scale structure of the resulting Pt layers on Au will be studied using HAADF-STEM-EDX elemental mapping as well as depth resolved XPS. Evidence is provided that the so-called Pt “monolayer” catalysts actually consist of 2-4 atom layers of Pt, often aggregated in small clusters. The effect of Pt cluster sizes on the Au surface and the tensile strain on Pt due to the underlying Au and their effect on EOR will be discussed. Using in-situ FTIR we also studied the catalytic EtOH activity of the catalysts and their ability to perform C-C bond splitting.1. Li, M.; Liu, P.; Adzic, R. R., Platinum Monolayer Electrocatalysts for Anodic Oxidation of Alcohols. J. Phys. Chem. Lett. 2012, 3, 3480-3485.2. Loukrakpam, R.; Yuan, Q. Y.; Petkov, V.; Gan, L.; Rudi, S.; Yang, R. Z.; Huang, Y. H.; Brankovic, S. R.; Strasser, P., Efficient C-C bond splitting on Pt monolayer and sub-monolayer catalysts during ethanol electro-oxidation: Pt layer strain and morphology effects. Phys. Chem. Chem. Phys. 2014, 16, 18866-18876.

Enhancing Alkaline Ethanol Oxidation on Ordered Intermetallic Pt3pb-Ptpb Core-Shell Nanoparticles Prepared by Converting Nanocrystalline Metals to Ordered Intermetallic Compounds

1. Introduction Recently, interest in direct fuel cells (DFCs) has increased in the field of polymer electrolyte membrane (PEM) fuel cells in which small organic molecule (SOM) liquid fuels, such as methanol (MeOH), ethanol (EtOH), and formic acid (FA), were used as fuels.1 Ethanol is a particularly attractive fuel because it has a lower toxicity, it is biogenerated, and it does not release carbon that was previously sequestered underground as coal, petroleum, or natural gas into the atmosphere.2 However, the full potential of DFCs has not been realised due to the slow kinetics in the anode reactions.3 Literature reports have described much faster oxidation kinetics for organic fuels in alkaline media than in acidic media.4 One of the research and development challenges for alkaline-type polymer electrolyte fuel cells (PEFCs) using SOMs is the design of better alternatives to the Pt, Pd, and Pt-Ru alloys currently used as the anode catalysts.5 To improve the electrocatalytic activity, Pt- and Pd-based alloy electrocatalysts have been investigated in alkaline media.6 Although the aforementioned alloys are promising materials, problems are associated with the use of disordered alloys (and alloys in general) as catalysts for fuel cell applications, including the low utilisation of the surface for electrocatalysis, the surface segregation of metal atoms, and the partial poisoning by CO due to insufficient quantities of the bimetallic elements on the surface. A new approach that prevents the problems inherent in disordered alloy catalysts has been proposed for highly active electrocatalysts for fuel cell applications.7 In contrast with a disordered alloy, intermetallic compounds with definite compositions and structures, such as PtPb and PtBi, exhibit excellent electrocatalytic performance for oxidising FA in acidic solutions in their onset potential for oxidation and current density.8,9 Abruña and co-workers have examined the FA, MeOH and EtOH oxidation activities for a wide range of intermetallic compounds in acidic media and found a significant number of the compounds, such as PtPb, PtBi and Pt3Ti, exhibit enhanced catalytic activities compared with pure Pt.8, 9 Our previous study indicated that the PtPb and PtBi ordered intermetallic compounds exhibited higher electrocatalytic activity for MeOH and EtOH oxidation in alkaline aqueous solutions than other Pt, Pt-Ru alloy and Pt-based ordered intermetallic compounds.10 In this paper, to enhance the electrocatalytic activity of PtPb ordered intermetallic compounds toward MeOH and EtOH in alkaline aqueous solutions, carbon black (CB)-supported Pt3Pb-PtPb intermetallic compound core-shell NPs were prepared via a two-step synthesis in which Pt3Pb-PtPb intermetallic compound core-shell NPs were formed on the CB through the reaction of the CB-supported Pt NPs and a Pb precursor in the presence of a reducing agent under microwave irradiation (Fig.1). The possibility of developing high-performance DFCs using Pt3Pb-PtPb intermetallic compound core-shell NPs as anode catalysts for alkaline EtOH oxidation is demonstrated. 2 . Results and Discussion We have successfully synthesised Pt3Pb-PtPb intermetallic compound core-shell NPs through a two-step synthesis in ethylene glycol under microwave irradiation. The pXRD, HX-PES and TEM/STEM characterisations demonstrated that pure PtPb NPs and Pt3Pb-PtPb intermetallic compound core-shell NPs could be prepared using one- and two-step syntheses, respectively, without requiring annealing. The Pt3Pb-PtPb intermetallic compound core-shell NPs exhibited higher catalytic activity for ethanol oxidation in alkaline aqueous solutions, enhanced tolerance for CO-poisoning and improved stability compared with commercial Pt NPs or pure PtPb NPs. 3 .

Controlling Carrier Densities in Photochemically Reduced Colloidal ZnO Nanocrystals: Size Dependence and Role of the Hole Quencher

Photodoped colloidal ZnO nanocrystals are model systems for understanding the generation and physical or chemical properties of excess delocalized charge carriers in semiconductor nanocrystals. Typically, ZnO photodoping is achieved photochemically using ethanol (EtOH) as a sacrificial reductant. Curiously, different studies have reported over an order of magnitude spread in the maximum number of conduction-band electrons that can be accumulated by photochemical oxidation of EtOH. Here, we demonstrate that this apparent discrepancy results from a strong size dependence of the average maximum number of excess electrons per nanocrystal, <nmax>. We demonstrate that <nmax> increases in proportion to nanocrystal volume, such that the maximum carrier density remains constant for all nanocrystal sizes. <nmax> is found to be largely insensitive to precise experimental conditions such as solvent, ligands, protons or other cations, photolysis conditions, and nanocrystal or EtOH concentrations. These results reconcile the broad range of literature results obtained with EtOH as the hole quencher. Furthermore, we demonstrate that <nmax> depends on the identity of the hole quencher, and is thus not an intrinsic property of the multiply reduced ZnO nanocrystals themselves. Using a series of substituted borohydride hole quenchers, we show that it is possible to increase the nanocrystal carrier densities over 4-fold relative to previous photodoping reports. When excess lithium and potassium triethylborohydrides are used in the photodoping, formation of Zn(0) is observed. The relationship between metallic Zn(0) formation and ZnO surface electron traps is discussed.

ChemInform Abstract: Synergistic Catalysis over Bimetallic Alloy Nanoparticles

AbstractReview: 215 refs.

Synergistic Catalysis over Bimetallic Alloy Nanoparticles

AbstractBimetallic nanoparticles (NPs) have emerged as an important class of catalysts. In many cases, bimetallic alloy NPs have higher catalytic efficiencies than their monometallic counterparts, owing to strong synergy between the metals. In this Review, we survey the research progress on the synergistic effect of bimetallic alloy NPs for catalytic reactions related to fuel cells, such as the electrochemical oxidation of MeOH, EtOH, and formic acid, CO oxidation, the oxygen‐reduction reaction, and the dehydrogenation of ammonia borane, formic acid, hydrous hydrazine, hydrazine borane, etc. In addition, the use of synergistic catalysis in some other important reactions has also been reviewed. Recent developments in synergistic catalysis over bimetallic alloy NPs will provide access to a variety of low‐cost and high‐performance catalysts for laboratory and industrial applications within the next few years.