Monolayer Electrocatalysts Research Articles

A novel arrangement of active and ultra-stable electrocatalyst based on iron/nickel/cobalt oxy/hydroxides for continuous oxygen evolution from alkaline seawater splitting

This research offers novel ideas for development a new class of materials with enhanced OER kinetics utilizing an easy electrochemical deposition technique. Here, the Ti/CoNiyOx/FeOOH electrocatalyst was prepared in two steps. First, CoNiyOx thin film was anodically electrodeposited on an activated titanium substrate. Then iron oxyhydroxide (FeOOH) nanosheets were cathodically electrodeposited on the first layer. The properties of this electrocatalyst was evaluated and compared with some monolayer electrocatalysts using field emission scanning electron microscopy (FE-SEM), Raman, energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and electrochemical methods. The Ti/CoNiyOx/FeOOH electrode requires an overpotential less than 330 mV at 100 mA/cm2 with Tafel constant of only 23.7 mV/dec for OER. The Ti/CoNiyOx/FeOOH electrode delivered long-term electrochemical stability in a solution containing corrosive chloride ions for more than 90 h at a constant current density of 100 mA/cm2 (with less than 9 % potential increase). Overall seawater splitting using the synthesized Ti/CoNiyOx/FeOOH electrode was performed at a current density of 100 mA/cm2 by a voltage as low as 1.58 V. The exceptional activity was ascribed to the synergistic effects of high electrochemical active sites and appropriate charge transfer ability found in CoNiyOx/FeOOH junction.

Ionic-liquid-induced phthalocyanine monolayer electrocatalyst for efficient nitrogen reduction reaction

The electrochemical NRR, which can be driven by renewable energy sources, is an emerging strategy for addressing the high energy consumption and CO2 emission issues caused by the traditional Haber–Bosch ammonia synthesis technique. FePc catalyzes the electrochemical ammonia synthesis reaction well, but intermolecular π-stacking and multi-layer overlapping lead to low NH3 yields. Here, [Bmim][Cl] and [Bmim][NTF2] ILs were used to induce monolayer dispersion of FePc. Ionic-liquid-induced FePc electrocatalyst, namely FePc/C-700, which was constructed with ILs as the carbon source, gave an excellent NH3 yield (24.25 μg mgcat−1 h−1) and Faradaic efficiency (30.59%) at − 0.1 V. The formation of a monolayer FePc structure was confirmed by HAADF-STEM and XANES. The results of DFT calculations and NRR experiments showed that the monolayer FePc structure promoted N2 adsorption and inhibited the competitive HER. These results will be useful in the design of active sites of layered macromolecules to achieve efficient electrochemical NRR.

Defect engineered Janus MoXTe (X=S, Se) monolayers for hydrogen evolution reaction: A first principles study

Given the elevated expense and constrained accessibility of platinum, the primary catalyst employed in electrocatalytic hydrogen evolution, it becomes essential to pinpoint an alternative catalyst demonstrating exceptional catalytic efficacy and broader scalability potential. In this study, we undertook an exhaustive inquiry into the electrocatalytic activity concerning hydrogen evolution of the monolayer Janus MoXTe (where X represents S and Se) utilizing first-principle calculation. Furthermore, an evaluation of the performance of defective MoXTe structures was conducted. Our findings illuminate that the incorporation of non-metallic elements like B, C, N, and P into MoXTe can be employed to finely adjust the Gibbs free energy (ΔGH) to approximately 0 eV. Particularly, the doping of B and P into the 1T phase of MoSTe (1T-MoSTe-B@ represents 1T phase of MoSTe-B@ and 1T-MoSTe-P@ represents 1T phase of MoSTe-P@), the doping of P into the 1T′ phase of MoSTe (1T′ phase of MoSTe-P@), and the doping of P into the 1T′ phase of MoSeTe (1T′ phase of MoSeTe-P@) exhibit ΔGH values that are in close proximity to zero (ΔGH = 0.02, −0.03, 0.06, and −0.14 eV, respectively). Through further analysis, we found that the pristine and defective structures all exhibit metallic properties. And the doping of P improved HER performance more effectively among four nonmetallic dopants. In details, H get 0.21, 0.29, 0.43 and 0.28 e on doping of B and P into 1T phase MoSTe (1T phase of MoSTe-B@ and 1T phase of MoSTe-P@) and the doping of P into 1T′ phase MoSeTe (1T’ phase of MoSeTe-P@). This study provides strategies for the design of MoXTe monolayer electrocatalysts, and it is expected to be applied to HER catalysts in affordable and efficient manner.

Catalytic activity for hydrogen evolution reaction of Janus monolayer MoXTe (X=S, Se)

At present, the precious metal Pt is a common catalyst for large-scale hydrogen evolution reaction (HER) production of hydrogen, but due to its high price and scarcity, finding an innovative catalyst has become the key to electrocatalytic hydrogen evolution. Here, the HER electrocatalytic activity of Janus MoXTe (X = S, Se) monolayers was investigated through first-principles calculations. Mo vacancy, X vacancy and Te vacancy were introduced into 2H, 1T, and 1T’ phase respectively and their stability was studied. The results show that the introduction of vacancy can improve the electrocatalytic hydrogen evolution performance. Particularly, the Gibbs free energies (ΔGH) of Te vacancy of 2H phase MoSTe and MoSeTe are close to zero (ΔGH = 0.03, −0.05 eV, respectively), and has the highest exchange current density. We further find that the conductivity of 2H phase MoSTe and MoSeTe is enhanced after introducing Te vacancy. In details, H get 1.86 and 1.43 e on VTe in 2H phase MoSTe and MoSeTe. The bond between S and H is more stable, H is better adsorbed on the catalyst, and the performance is improved. Our research provides a strategy for designing MoXTe monolayer electrocatalysts, which are predicted to be employed in HER catalysts with low cost and high performance.

Dual‐Site Functionalization on Supported Metal Monolayer Electrocatalysts for Selective CO2 Reduction (Adv. Energy Mater. 3/2023)

CO2 Electroreduction In article number 2203138, Zhonglong Zhao and Gang Lu predict that noble metal monolayers supported by transition metal carbides (TMCs) and nitrides (TMNs) could be selective catalysts for the carbon dioxide reduction reaction with suppressed hydrogen evolution reaction. Dual-site functionalization induced by antibonding interactions between hydrogen and the TMC/TMN substrates is identified, which can circumvent energy scaling relations and enable active, selective, and robust CO2 electroreduction.

Dual‐Site Functionalization on Supported Metal Monolayer Electrocatalysts for Selective CO2 Reduction

AbstractDevelopment of efficient catalysts for electrochemical carbon dioxide reduction reaction (CO2RR) represents a great challenge in renewable energy research. Although noble metals have long been explored as catalysts for CO2RR, their reactivity and selectivity remain rather low owing to the competing hydrogen evolution reaction (HER). Here, this work proposes that noble metal monolayers (MLs) supported by transition metal carbides (TMCs) and nitrides (TMNs) can become exceptional CO2RR catalysts with much suppressed HER. This work shows that there is a direct, antibonding interaction between the hydrogen adsorbate and the TMC/TMN substrates, while such interactions between CO2RR intermediates and the substrates are absent. This difference enables dual‐site functionalization of the ML catalysts, which circumvents the energy scaling relations dictating the competition between CO2RR and HER. Consequently, it is possible to reduce the binding of the H adsorbate to suppress HER and simultaneously increase the binding of CO2RR intermediates to boost the CO2RR. This work identifies several Ag and Au‐based catalysts that are thermodynamically and electrochemically stable and exhibit high activity and selectivity toward the production of formic acid. In addition, this work predicts that higher order CO2RR products including methanol and ethylene can also be produced on selected catalysts.

Activation of MoS2 monolayer electrocatalysts via reduction and phase control in molten sodium for selective hydrogenation of nitrogen to ammonia

Electrochemical nitrogen fixation under ambient conditions is promising for sustainable ammonia production but is hampered by high reaction barrier and strong competition from hydrogen evolution, leading to low specificity and faradaic efficiency with existing catalysts. Here we describe the activation of MoS2 in molten sodium that leads to simultaneous formation of a sulfur vacancy-rich heterostructured 1T/2H-MoSx monolayer via reduction and phase transformation. The resultant catalyst exhibits intrinsic activities for electrocatalytic N2-to-NH3 conversion, delivering a faradaic efficiency of 20.5% and an average NH3 rate of 93.2 μg h−1 mgcat−1. The interfacial heterojunctions with sulfur vacancies function synergistically to increase electron localization for locking up nitrogen and suppressing proton recombination. The 1T phase facilitates H–OH dissociation, with S serving as H-shuttling sites and to stabilize . The subsequently couple with nearby N2 and NHx intermediates bound at Mo sites, thus greatly promoting the activity of the catalyst. First-principles calculations revealed that the heterojunction with sulfur vacancies effectively lowered the energy barrier in the potential-determining step for nitrogen reduction, and, in combination with operando spectroscopic analysis, validated the associative electrochemical nitrogen reduction pathway. This work provides new insights on manipulating chalcogenide vacancies and phase junctions for preparing monolayered MoS2 with unique catalytic properties.

Circumventing the scaling relationship on bimetallic monolayer electrocatalysts for selective CO2 reduction.

Electrochemical conversion of CO2 into value-added chemicals continues to draw interest in renewable energy applications. Although many metal catalysts are active in the CO2 reduction reaction (CO2RR), their reactivity and selectivity are nonetheless hindered by the competing hydrogen evolution reaction (HER). The competition of the HER and CO2RR stems from the energy scaling relationship between their reaction intermediates. Herein, we predict that bimetallic monolayer electrocatalysts (BMEs) – a monolayer of transition metals on top of extended metal substrates – could produce dual-functional active sites that circumvent the scaling relationship between the adsorption energies of HER and CO2RR intermediates. The antibonding interaction between the adsorbed H and the metal substrate is revealed to be responsible for circumventing the scaling relationship. Based on extensive density functional theory (DFT) calculations, we identify 11 BMEs which are highly active and selective toward the formation of formic acid with a much suppressed HER. The H–substrate antibonding interaction also leads to superior CO2RR performance on monolayer-coated penta-twinned nanowires.

Platinum Monolayer Electrocatalysts

Platinum Monolayer Electrocatalysts

Platinum Monolayer Electrocatalysts

Explained here is the new approach of designing electrocatalysts with dramatically reduced Pt content while enhancing catalytic performance that entails a nanoparticle of another metal covered by a monolayer of platinum. A monolayer of Cu is formed by underpotential deposition (UPD) on a metal core, followed by galvanic displacement of Cu atoms by Pt ions. Pt monolayer on Pd substrate can be formed by controlled reduction of Pt2+ by ethanol, and by controlled surface-mediated growth by cycling potential between Cu and Pt bulk deposition. Besides the ultimately low Pt content and complete utilization of Pt atoms in the reaction, this method allows tunable activity induced by substrate electronic and geometric structure. The morphology of nanoparticles and their performance were characterized by X-ray absorption spectroscopy, infrared spectroelectrochemistry, and rotating disk electrode, and the principles of operation were summarized.

Platinum and Palladium Monolayer Electrocatalysts for Formic Acid Oxidation

The direct formic acid fuel cell holds great promise as a next generation portable power source. Here we report an experimental study on Pt and Pd monolayer (Pt* and Pd*) atop the close-packed facet of transition metal substrates (denoted Pt*/M or Pd*/M, where M = Pt, Pd, Ir, Au, Rh and Ru) model catalysts for formic acid oxidation (FAO) and demonstrate a promotional effect on Pt*/Au(111) and Pd*/Pt(111) surfaces. Contrary to findings on monometallic surfaces, in situ infrared reflection adsorption spectroscopy collected during formic acid oxidation at potentials anodic of 375 mV reveal that the poisoning reaction intermediate CO is not formed on the monolayer surfaces, suggesting a promotion of the direct mechanisms of FAO at the expense of the indirect mechanism through CO. Our density functional theory calculations on model surfaces with 1:1 stoichiometry for overlayer to support metal atoms for the thermochemistry of the elementary steps defined by adsorbed CO, OH, COOH, and HCOO on the (111) facet of Pt, PtML/Au, Pd, and PdML/Pt largely attribute the promotional effect observed for the monolayer catalysts to easier removal of CO brought about by easier activation of water, relative to the monometallic catalysts. This synergy between experiments and theory brings us closer to a fundamental understanding of FAO electrocatalysts under reaction conditions, paving the way to achieving more active electrocatalysts possibly with less Pt or Pd; a pre-requisite for the mass commercialization of this technology.

Single-Metal Atom Anchored on Boron Monolayer (β12) as an Electrocatalyst for Nitrogen Reduction into Ammonia at Ambient Conditions: A First-Principles Study

On the basis of the first-principles calculation, single transition-metal (TM) atoms of first and second transition series are anchored on the β12 phase of the boron monolayer (BM) electrocatalyst ...

(Keynote) Theoretical Inspirations from Radoslav Adzic’s Electrocatalysis Work

When combined with controlled synthesis of well-defined facets and shapes, density functional theory (DFT) could give especially accurate descriptions of electrocatalytic reactions on surfaces. Dr. Adzic’s group has pioneered the controlled and uniform deposition of a monolayer (or overlayers) of Pt on a single crystal or nanoparticles of another transition metal or transition metal alloys.1-6 Not only does this morphology achieve better utilization of the overlying Pt atoms, but the resulting structures also possess remarkable stability as electrocatalysts. Here, we review our long-standing collaboration with Dr. Adzic on the oxygen reduction reaction (ORR) over Pt monolayer or overlayers atop a variety of transition metals5,7-12, as well as the electrooxidation of formic acid on Pt monolayers on single-crystals of transition metals. A logical extension of this methodology is to support Pt overlayers atop shape-selected nanoparticles, which selectively expose well-defined facets. Time-permitting, we will also be discussing insights from studying ORR of Pt overlayers on Pd icosahedra13, octahedra14, and nanocubes15. In several cases, the induced compressive strain and ligand effects that the Pt monolayer or overlayers experience on various substrates weaken the adsorption of oxygenated species (e.g.: OH) compared to pure Pt, thereby enhancing the ORR activity. Zhang J, Mo Y, Vukmirovic MB, Klie R, Sasaki K, Adzic RR. Platinum monolayer electrocatalysts for O-2 reduction: Pt monolayer on Pd(111) and on carbon-supported Pd nanoparticles. J. Phys. Chem. B. Jul 29 2004;108(30):10955-10964. Sasaki K, Naohara H, Cai Y, et al. Core-Protected Platinum Monolayer Shell High-Stability Electrocatalysts for Fuel-Cell Cathodes. Angew. Chem. Int. Ed. 2010;49(46):8602-8607. Adzic R. Platinum Monolayer Electrocatalysts: Tunable Activity, Stability, and Self-Healing Properties. Electrocatalysis. Dec 2012;3(3-4):163-169. Bliznakov ST, Vukmirovic MB, Yang L, Sutter EA, Adzic RR. Pt Monolayer on Electrodeposited Pd Nanostructures: Advanced Cathode Catalysts for PEM Fuel Cells. Journal of the Electrochemical Society. 2012;159(9):F501-F506. Knupp SL, Vukmirovic MB, Haldar P, Herron JA, Mavrikakis M, Adzic RR. Platinum Monolayer Electrocatalysts for O-2 Reduction: Pt Monolayer on Carbon-Supported PdIr Nanoparticles. Electrocatalysis. Dec 2010;1(4):213-223. Sasaki K, Wang JX, Naohara H, et al. Recent advances in platinum monolayer electrocatalysts for oxygen reduction reaction: Scale-up synthesis, structure and activity of Pt shells on Pd cores. Electrochimica Acta. Mar 2010;55(8):2645-2652. Yang L, Vukmirovic MB, Su D, et al. Tuning the Catalytic Activity of Ru@Pt Core-Shell Nanoparticles for the Oxygen Reduction Reaction by Varying the Shell Thickness. J. Phys. Chem. C. Jan 31 2013;117(4):1748-1753. Herron JA, Jiao J, Hahn K, Peng G, Adzic RR, Mavrikakis M. Oxygen Reduction Reaction on Platinum-Terminated "Onion-structured" Alloy Catalysts. Electrocatal. Dec 2012;3(3-4):192-202. Zhou W-P, Yang X, Vukmirovic MB, et al. Improving Electrocatalysts for O-2 Reduction by Fine-Tuning the Pt-Support Interaction: Pt Monolayer on the Surfaces of a Pd3Fe(111) Single-Crystal Alloy. J. Am. Chem. Soc. Sep 9 2009;131(35):12755-12762. Vukmirovic MB, Zhang J, Sasaki K, et al. Platinum monolayer electrocatalysts for oxygen reduction. Electrochim. Acta. Jan 20 2007;52(6):2257-2263. Adzic RR, Zhang J, Sasaki K, et al. Platinum monolayer fuel cell electrocatalysts. Topics in Catalysis. Dec 2007;46(3-4):249-262. Zhang JL, Vukmirovic MB, Xu Y, Mavrikakis M, Adzic RR. Controlling the catalytic activity of platinum-monolayer electrocatalysts for oxygen reduction with different substrates. Angewandte Chemie-International Edition. 2005;44(14):2132-2135. Wang X, Choi S-I, Roling LT, et al. Palladium-platinum core-shell icosahedra with substantially enhanced activity and durability towards oxygen reduction. Nature Commun. Jul 2015;6. Park J, Zhang L, Choi S-I, et al. Atomic Layer-by-Layer Deposition of Platinum on Palladium Octahedra for Enhanced Catalysts toward the Oxygen Reduction Reaction. Acs Nano. Mar 2015;9(3):2635-2647. Xie S, Choi S-I, Lu N, et al. Atomic Layer-by-Layer Deposition of Pt on Pd Nanocubes for Catalysts with Enhanced Activity and Durability toward Oxygen Reduction. Nano Lett. Jun 2014;14(6):3570-3576.

(Invited) Retrospective on Oxygen Reduction Electrocatalyst R&D Supported By the U.S. Department of Energy

Fuel cells are highly efficient energy conversion devices; they can operate on fuels such as natural gas, methane, and methanol as well as hydrogen generated using diverse domestic resources. Fuel cells are efficient, scalable, and can be used in a variety of applications - from the transportation sector to the generation of primary and secondary power. The U.S. Department of Energy’s (DOE's) Hydrogen and Fuel Cell Program supports early-stage research and development leading to energy security and resiliency, paving the way to a strong domestic economy. Because reducing cost and increasing durability remain as the major challenges in the advancement of fuel cell technology, early-stage R&D includes improvements in performance and durability and lower cost catalysts as well as membrane electrode assemblies for fuel cells and electrolyzers. This presentation will describe the development of oxygen reduction catalysts for fuel cells focusing on the tremendous achievements from Dr. Adzic of Brookhaven National Laboratory. His association with DOE's Office of Energy Efficiency and Renewable Energy began in 2003 with the introduction of Platinum Monolayer Electrocatalysts and was extended to the broader concept of core-shell catalysts. As just a single recent example of the promise of the catalysts, Dr. Adzic and his team recently found that nitriding core components, such as NiPd alloy, in core-shell electrocatalysts resulted in a 50% reduction in Pd content compared to extant Pt/Pd/C catalysts and enhanced overall stability and activity. As a whole, the core shell catalysts have captured the attention of the industry and beyond resulting in U.S. patents, some of which have been licensed to catalyst producers. Other research groups have adopted BNL's concept of core-shell catalysts as well as the use of gold for increasing durability in catalysts. Not surprisingly, R&D 100 and many other awards have followed.

New Nitride-Stabilized Cores for Platinum Monolayer Electrocatalysts for the Oxygen Reduction Reaction

Pt monolayer (ML) electrocatalysts offer a dramatically reduced Pt content while providing considerable possibilities for enhancing their catalytic activity and stability for the oxygen reduction reaction (ORR) at fuel cell (FC) cathodes. The achievements in highly active, stable Pt ML on Pd-based nanoparticle catalysts for the ORR have been described elsewhere1-3. Various spectroscopic and microscopic studies coupled with theoretical calculations have revealed that their high advantageous characteristics resulted from the geometric and electronic interactions between the cores and the Pt MLs, together with the self-healing effect induced by the supporting cores. In order to further improve the electrochemical performance and reduce total costs toward commercialization, the composition, shape, and size of cores need to be optimized. Recently we have developed several novel nanostructured cores, such as Ir-based core-shell and alloy cores4, nitride-stabilized core components5-7, and structurally ordered intermetallic cores8to enhance the properties of the Pt ML shells. In the present paper, we will focus on the results of newly-developed nitride cores for the Pt ML electrocatalysts and discuss potentials of the approach. We believe that the results from the Pt ML electrocatalysts significantly impact the research of electrocatalysis and FC technology, as they demonstrate an exceptionally effective way of using Pt that can resolve problems encountered in other approaches. Acknowledgements: This manuscript has been authored by employees/guest of Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. The publisher by accepting the manuscript for publication acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes.

Tuning electrocatalytic activity of Pt monolayer shell by bimetallic Ir-M (M=Fe, Co, Ni or Cu) cores for the oxygen reduction reaction

Platinum monolayer electrocatalyst are known to exhibit excellent oxygen reduction reaction (ORR) activity depending on the type of substrate used. Here we demonstrate a relationship between the ORR electrocatalytic activity and the surface electronic structure of Pt monolayer shell induced by various IrM bimetallic cores (M=Fe, Co, Ni or Cu). The relationship is rationalized by comparing density functional theory calculations and experimental results. For an efficient Pt monolayer electrocatalyst, the core should induce sufficient contraction to the Pt shell leading to a downshift of the d-band center with respect to the Fermi level. Depending on the structure of the IrM, relative to that of pure Ir, this interaction not only alters the electronic and geometric structure but also induces segregation effects. Combined these effects significantly enhance the ORR activities of the Pt monolayer shell on bimetallic Ir cores electrocatalysts.

Pt Sub-Monolayer on Au: System Stability and Insights into Platinum Electrochemical Dissolution

Platinum is the best single element oxygen reduction reaction electrocatalyst. In recent years, several advanced catalysts have been suggested. One of them is the so-called “platinum monolayer electrocatalyst”. In this work we demonstrate the potential- and time-resolved dissolution characteristics of such sub-monolayer platinum supported on gold in potentiodynamic and potentiostatic regimes. It is shown that the as-prepared Pt@Au is not stable, but rather shows significant dissolution of both Pt and Au similar to the pure elements. Potential-resolved dissolution profiles reveal that anodic dissolution scales with Pt coverage, while cathodic dissolution and quasi-steady-state dissolution are Pt coverage independent. This implies a significantly higher Pt coverage normalized dissolution of Pt@Au, viz. a factor of four higher dissolution amounts for Pt coverage of 0.25. The onsets of Pt and Au dissolution are also comparable to the pure elements. Only after intermixing during potential cycling does the system become somewhat stabilized. The onset of Pt transient anodic dissolution shifts to more positive values. The data obtained in the current work provide new insights into the mechanism of platinum dissolution. It also aids the understanding of the previously observed effect of stabilization of Pt catalysts by addition of Au, and will therefore guide future developments for improving catalyst performance.

Synchrotron-Based In Situ Characterization of Carbon-Supported Platinum and Platinum Monolayer Electrocatalysts

A detailed understanding of oxidation/dissolution mechanisms of Pt is critical in designing durable catalysts for the oxygen reduction reaction (ORR), but exact mechanisms remain unclear. The present work explores the oxidation/dissolution of Pt and Pt monolayer (ML) electrocatalysts over a wide range of applied potentials using cells that facilitate in situ measurements by combining X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) measurements. The X-ray absorption near edge structure (XANES) measurement demonstrated that Pt nanoparticle surfaces were oxidized from metallic Pt to α-PtO2-type oxide during the potential sweep from 0.41 to 1.5 V, and the transition state of O or OH adsorption on Pt and the onset of the place exchange process were revealed by the delta mu (Δμ) method. Only the top layers of Pt nanoparticles were oxidized, while the inner Pt atoms remained intact. At a higher potential over 1.9 V, α-PtO2-type surface oxides dissolve due to local acidification caused by the oxyg...

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.

Pt Monolayer Electrocatalyst for Oxygen Reduction Reaction on Pd-Cu Alloy: First-Principles Investigation

First principles approach is used to examine geometric and electronic structure of the catalyst concept aimed to improve activity and utilization of precious Pt metal for oxygen reduction reaction in fuel cells. The Pt monolayers on Pd skin and Pd1-xCux inner core for various compositions x were examined by building the appropriate models starting from Pd-Cu solid solution. We provided a detailed description of changes in the descriptors of catalytic behavior, d-band energy and binding energies of reaction intermediates, giving an insight into the underlying mechanism of catalytic activity enhancement based on the first principles density functional theory (DFT) calculations. Structural properties of the Pd-Cu bimetallic were determined for bulk and surfaces, including the segregation profile of Cu under different environment on the surface.