Surface Atomic Composition Research Articles

Atomic-Level Observation of Potential-Dependent Variations at the Surface of an Oxide Catalyst during Oxygen Evolution Reaction.

Understanding the intricate details of the surface atomic structure and composition of catalysts during the oxygen evolution reaction (OER) is crucial for developing catalysts with high stability in water electrolyzers. While many notable studies highlight surface amorphization and reconstruction, systematic analytical tracing of the catalyst surface as a function of overpotential remains elusive. Heteroepitaxial (001) films of chemically stable and lattice-oxygen-inactive LaCoO3 are thus utilized as a model catalyst to demonstrate a series of atomic-resolution observations of the film surface at different anodic potentials. The first key finding is that atoms at the surface are fairly dynamic even at lower overpotentials. Angstrom-scale atomic displacements within the perovskite framework are identified below a certain potential level. Another noteworthy feature is that amorphization (or paracrystallization) with no long-range order is finally induced at higher overpotentials. In particular, surface analyses consistently support that the oxidation of lattice oxygen is coupled with amorphous phase formation at the high potentials. Theoretical calculations also reveal an upward shift of oxygen 2p states toward the Fermi level, indicating enhanced lattice oxygen activation when atom displacement occurs more extensively. This study emphasizes that the degradation behavior of OER catalysts can distinctively vary depending on the overpotential level.

Probing water adsorption characteristics of Pt step-edge decorated Cu(211) surface

The surface structure and atomic composition can affect the adsorption characteristics of water on metal surfaces. In this study, we investigated the adsorption of water on Cu(211) stepped surfaces decorated with Pt by a combination of infrared reflection absorption spectroscopy (IRRAS) and temperature-programmed desorption (TPD) studies. We have observed that step sites of Cu can increase the strength of the binding of water molecules to the surface and facilitate water partial dissociation and the formation of OH groups on the surface. Step decoration by Pt can change the water adsorption characteristics and eliminate the water dissociation. Water adsorbs molecularly on the fully Pt-decorated steps of the Cu(211) surface. Molecular water and OH adsorbed on Cu(211), which can make a chain structure, are disrupted with Pt atoms.

Bifunctional TiCo electrocatalysts based on N-doped graphene cryogels for the oxygen evolution and reduction reactions

Three-dimensional N-doped graphene cryogels (NGC) modified with Ti and Co nanoparticles are investigated as bifunctional oxygen electrocatalysts for potential application in unitized regenerative fuel cells (URFCs). These composites have been successfully produced via a combined solvothermal, freeze-drying, and thermal treatment procedure. Crystallographic structure, surface properties, and morphology are analyzed to study the influence of each metal and the bimetallic combination in forming active sites for oxygen reduction (ORR) and oxygen evolution (OER) reactions. The intrinsic catalytic activity of the composites was determined by rotating disk electrode and further assessed in a gas diffusion electrode to test them in more realistic conditions for URFCs in 6 M KOH. Results revealed the remarkable bifunctional activity of Co/NGC and bimetallic TiCo/NGC composites. The synergistic effect of the metallic cobalt and surface atomic composition of Co3O4 distributed on the N-doped graphene cryogel in Co/NGC is responsible for the high bifunctional performance. Moreover, the partial substitution of cobalt for a less critical raw material, such as titanium, allows the electrocatalyst to maintain great bifunctional activity and stability. The nitrogen doping of the graphene cryogel structure can influence the anatase/rutile titania ratio that forms during pyrolysis. As a result, defects, oxygen vacancies, and Ti3+ species are formed, which, when combined with Co nanoparticles, contribute to the outstanding performance and stability of the TiCo/NGC composite. The excellent performance of N-doped graphene cryogel-based electrocatalysts in GDE conditions indicates their potential use in electrochemical processes, which involve gas-phase reactions.

Influence of titanium nanoscale surface roughness on fibrinogen and albumin protein adsorption kinetics and platelet responses.

Biomaterials with nanoscale topography have been increasingly investigated for medical device applications to improve tissue-material interactions. This study assessed the impact of nanoengineered titanium surface domain sizes on early biological responses that can significantly affect tissue interactions. Nanostructured titanium coatings with distinct nanoscale surface roughness were deposited on quartz crystal microbalance with dissipation (QCM-D) sensors by physical vapor deposition. Physico-chemical characterization was conducted to assess nanoscale surface roughness, nano-topographical morphology, wettability, and atomic composition. The results demonstrated increased projected surface area and hydrophilicity with increasing nanoscale surface roughness. The adsorption properties of albumin and fibrinogen, two major plasma proteins that readily encounter implanted surfaces, on the nanostructured surfaces were measured using QCM-D. Significant differences in the amounts and viscoelastic properties of adsorbed proteins were observed, dependent on the surface roughness, protein type, protein concentration, and protein binding affinity. The impact of protein adsorption on subsequent biological responses was also examined using qualitative and quantitative in vitro evaluation of human platelet adhesion, aggregation, and activation. Qualitative platelet morphology assessment indicated increased platelet activation/aggregation on titanium surfaces with increased roughness. These data suggest that nanoscale differences in titanium surface roughness influence biological responses that may affect implant integration.

Feasibility of nitrate adsorption from aqueous solution by nitrogen and oxygen-modified pine bark biochar: experimental and computational approach

Efficient and economical wastewater treatment has presented itself as a global challenge. In this context, adsorption is one of the most effective methods to remove contaminants from wastewater. The present study evaluated the feasibility of chemically modified pine bark biochar’s nitrate adsorption ability. Pine bark biochar was modified with urea and sulfuric acid to remove nitrate from an aqueous solution. The physicochemical properties of the biochar samples, such as pH, pH at point of zero charges, surface atomic composition, surface morphology, and surface area, were evaluated. The equilibrium adsorption data were fitted to the Langmuir and Freundlich isotherm models. The kinetic data were fitted to different kinetic models (pseudo-first order, pseudo-second order, intraparticle diffusion, and Elovich). The adsorption data fitted well with the Langmuir and pseudo-first order models. The maximum nitrate adsorption capacity was found to be 1.548 mg g−1. Mass transfer studies were conducted to identify the rate-limiting step, values of the external mass transfer coefficient, and diffusion coefficient in the nitrate adsorption process by the modified biochar. The external mass transfer coefficients were in the range of 2.2 × 10–11–2.86 × 10–10 m s−1. The intraparticle diffusion coefficient ranged from 6.53 × 10–10 to 1.78 × 10–9 m2 s−1. The Biot number value less than 100 indicated that the adsorption was controlled by film diffusion. Interaction energies between nitrate ions and model biochar structures were calculated DFT-based quantum chemical software (Gaussian). The positive interaction energy values (2.3485–2.485 eV) suggested nitrate adsorption on model biochar structures was thermodynamically not feasible.Graphical

Hydrogen Evolution Reaction on AuNi Surface Alloy Formed on Single Crystal Au Electrodes

AbstractThe hydrogen evolution reaction (HER) on Au with high chemical stability is activated by alloying it with Ni. We evaluated the HER activity of the AuNi surface alloy prepared at different alloying temperatures on single‐crystal Au electrodes in 0.05 M H2SO4. The potential cycle, including the region of Ni oxidative dissolution, further enhanced the HER activity by dealloying Ni, and the activity depended on the surface structure of the Au substrate in the following order: AuNi/Au(100)<AuNi/Au(111)<AuNi/Au(110). The surface structure and atomic composition were investigated using X‐ray photoelectron spectroscopy and surface X‐ray diffraction. Surface structural analysis revealed that the dissolution of Ni from the AuNi surface‐alloy layer resulted in a decrease in the atomic occupancy of the topmost surface layer. Ni dealloying creates low‐coordination Au sites on the AuNi surface alloy, which activates the HER.

Boosting Catalytic Oxidative Desulfurization Performance over Yolk-Shell Nickel Molybdate Fabricated by Defect Engineering.

Developing catalysts with optimized surface properties is significant for advanced catalysis. Herein, a rational architectural design is proposed to successfully synthesize yolk-shell nickel molybdate with abundant oxygen vacancies (YS-VO-NMO) via an acid-assisted defect engineering strategy. Notably, YS-VO-NMO with the yolk-shell structure shows complex nanoconfined interior space, which is beneficial to the mass transfer and active sites exposure. Moreover, the defect engineering strategy is of great importance to modulate the surface electronic structure and atomic composition, which contributes to the enrichment of oxygen vacancies. Benefiting from these features, the higher hydrogen peroxide activation is achieved by YS-VO-NMO to produce more hydroxyl radicals compared with untreated nickel molybdate. Consequently, the defect-engineered YS-VO-NMO not only features superior catalytic activity (99.5%) but also retains high desulfurization efficiency after recycling eight times. This manuscript provides new inspiration for designing more promising defective materials via defect engineering and architecture for different applications besides oxidative desulfurization.

A Perfluorocarbon-Coated ZrP Cation Exchanger with Excellent Ammonium Selectivity and Chemical Stability: An Oral Sorbent for End-Stage Kidney Disease (ESKD).

An oral sorbent to remove NH4+ within the small intestine of end-stage kidney disease (ESKD) patients could reduce blood urea levels and diminish their dialysis treatment burden. But current sorbent materials like amorphous zirconium phosphate particles Zr(HPO4)2·H2O (ZrP) lack the selectivity to remove NH4+ in water solution with other competing ions. Our previous work found that a gas-permeable, hydrophobic polydimethylsiloxane (PDMS) coating on ZrP improved the material's selectivity for NH4+. However, a competing ion Ca2+ was still removed by PDMS-coated ZrP sorbent, and the permeability of the PDMS coating to Ca2+ was increased after low-pH stomach-like condition exposure. An alternative hydrophobic and gas permeable coating has been investigated─perfluorooctyltriethoxysilane (FOTS). The coating was attached in place of PDMS to a tetraethyl orthosilicate-coated ZrP surface. Surface atomic composition analysis and scanning electron microscopy observation verified the successful application of the FOTS coating. Water contact angle analysis validated the FOTS coating was hydrophobic (145.0 ± 3.2°). In vitro competing ion studies indicated the FOTS coating attached to ZrP increased NH4+ removal by 53% versus uncoated ZrP. FOTS offers complete selectivity for NH4+ over Ca2+ with similar NH4+ capacity as the previous PDMS coating. Moreover, FOTS-coated ZrP maintained NH4+ removal capacity and selectivity after the acid exposure study, indicating excellent acid resistance while NH4+ selectivity of ZrP-PDMS decreased by 72%. The results suggested that FOTS-coated ZrP is promising as an oral sorbent for ESKD patients.

Ethanol Dry Reforming over Bimetallic Ni‐Containing Catalysts Based on Ceria‐Zirconia for Hydrogen Production

AbstractMixed Ce−Zr oxides with a fluorite structure were synthesized by the solvothermal method in a supercritical medium of isopropanol. The prepared mixed oxides Ce0.5Zr0.5O2 and Ce0.75Zr0.25O2 were used as supports for 5 wt%Ni and bimetallic 2.5 wt%Ni+2.5 wt%Co catalysts. The catalysts were fully characterized (specific surface area, morphology, particle size, phase composition, surface atomic composition) and tested in ethanol dry reforming.The dependences of the conversion of C2H5OH and CO2, the yield of CO and H2, and the H2/CO ratio were estimated. The effect of the supported metals interaction and the effect of Ce/Zr ratio in the support on the catalytic activity were shown. The presence of nickel in the composition of the catalyst is necessary for high catalytic activity. It has been shown that the addition of cobalt cannot contribute to increase the catalytic activity and stability, but helps to decrease the deposition of carbon and significantly reduces the rate of carbon formation during ethanol dry reforming comparing to the monometallic nickel material.

Design of grain boundaries enriched nickel molybdate for enhanced catalytic oxidative desulfurization

Grain boundaries (GB), a favorable atomic configuration, can provide highly active surfaces by modulating electronic structures in the catalysts. Whereas, it is usually be ignored owing to the large structural variations and the difficulty in its precise design. Herein, a novel strategy is proposed to prepare nickel molybdate with rich GB (RGB-NMO) via a facile one-step growth assisted by cetyltrimethylammonium bromide. Experimental results reveal that the optimized morphology can increase the exposure of active sites and facilitate the mass transfer during the oxidative desulfurization (ODS) reaction. Moreover, the engineered GB can modulate the surface atomic composition and electronic structure, leading to the increase of hydrogen peroxide activation capacity. Benefiting from these features, the synthesized RGB-NMO not only exhibits attractive desulfurization efficiency, but also shows a satisfactory cycling stability. Overall, this manuscript provides new inspirations for design of functional materials rich in GB towards excellent ODS treatment.

Depth profiling of AlN and AlxGa1−xN crystals by XPS using Al Kα and Ag Lα line excitation and Ar ion gas cluster ion source

AlGaN-based heterostructures are promising candidates for the fabrication of ultraviolet light-emitting diodes. The analysis of the atomic composition of the grown epitaxial films is important from a technological point of view, allowing precise control over the wavelength and intensity of the emitted light. In this work, the depth profiling of AlN(0001), AlGaN(0001), and AlGaN quantum dot surfaces grown by molecular beam epitaxy was carried out by using angle-resolved x-ray photoelectron spectroscopy (XPS) combined with Ar gas cluster ion source (GCIS) sputtering. Core level shifts in XPS spectra measured by Al Kα and Ag Lα photon sources were determined. We found that sputtering by Ar1000+ ion clusters with an energy of 10 keV creates disorder on the surface and induces changes in surface atomic composition. As a result, depth profiling with a typical surface-sensitive Al Kα photon source is affected by the damaged layer. The application of a less surface-sensitive Ag Lα photon source with high photon energy could suppress the contribution from the damaged surface layer. Combining GCIS sputtering with Ag Lα line XPS measurements is, therefore, very promising for the quantification of atomic composition in the buried epitaxial layers or heterostructures with thicknesses of several tens of nm.

Modulating Electronic Characteristics of Nickel Molybdate via an Effective Manganese-Doping Strategy to Enhance Oxidative Desulfurization Performance

Modulating the electronic characteristics of catalysts plays a significant role in optimizing their catalytic activity. Herein, Mn-doped nickel molybdate (MNMO) nanorods are synthesized via replacing the partial Ni sites by the Mn element, engineering a bimetallic synergistic effect to enhance the activation of oxygen (O2). Compared with the extremely low catalytic activity of pristine nickel molybdate (NiMoO4), complete desulfurization can be achieved by MNMO under the same reaction conditions. Characterization results show that the electronic structure and surface atomic composition of pure NiMoO4 will be modulated owing to the introduction of Mn atoms, leading to the enhancement of the oxygen vacancy content and stronger O2 activation capacity. Besides, the optimized catalyst MNMO-20 also displays satisfactory cycle performance, and the sulfur removal of dibenzothiophene still maintains 96.1% after six times of recycling. The distinctive engineering strategy and simple synthesis method provide a new insight in designing and developing oxidative desulfurization catalysts with high stability and effectivity.

Precipitation of Ferrous Oxalate from Ferrous Ammonium Sulfate in Oxalic Acid Solution

A kinetic study was conducted experimentally for the precipitation of ferrous oxalate. The ferrous oxalate, in the form of dihydrate (FeC2O4·2H2O), was produced by the acidic dissolution of ferrous ammonium sulfate (Fe(NH4)2(SO4)2) in an aqueous solution of oxalic acid, and then precipitated by nucleation and particle growth from supersaturated solution. The effect of the concentration of ferrous ammonium sulfate and oxalic acid as raw materials was investigated on the kinetics of the ferrous oxalate precipitation. Temperature was kept constant at 25 °C. The surface morphology, atomic compositions, and crystal phase were characterized for the ferrous oxalate precipitate collected. As the initial concentration of ferrous ammonium sulfate increased, the initial precipitation of ferrous oxalate occurred faster. The concentration of oxalic acid did not significantly affect the rate of precipitation of ferrous oxalate. The experimental behavior of ferrous oxalate precipitation was modeled with first-order models of reaction kinetics.

Unraveling the structure and composition sensitivity of transition metal phosphide toward catalytic performance of C2H2 semi-hydrogenation

To unravel the structure and composition sensitivity of transition metal phosphides (MxPy) to C2H2 semi-hydrogenation catalytic performance, a series of MxPy (M = Mo, W, Fe, Co, Ni and Pd) with different crystal facet, exposed termination, and M: P ratio are fully examined. DFT calculations and microkinetic modeling show that C2H4 selectivity and activity over MxPy catalysts are sensitive to surface atomic structure and composition, attributing to different electronic properties. C2H2 adsorption energy is verified as good descriptor to evaluate C2H4 formation rate. FeP(101)-I catalyst is screened out to present Pd-like performance with higher C2H4 formation rate, higher C2H4 selectivity and greater stability against green oil formation than the Pd and other MxPy catalysts, which is still superior to the previously reported catalysts, such as the metal oxide, metal alloy and MxSy, as well as comparable to intermetallic compound. The results could supply a valuable clue for designing and optimizing MxPy catalysts in C2H2 semi-hydrogenation.

Immobilization of Fe2O3 on perlite for photo-Fenton degradation of methylene blue

Photo-Fenton catalysts with floating features based on the immobilization of Fe2O3 particles on the surface of perlite granules were synthesized by a simple precipitation-annealing method. The effects of annealing temperature on the crystal structure, phase composition, morphology, surface area, surface functional groups, and surface atomic composition of the prepared catalysts were investigated by powder X-ray diffraction, field emission scanning electron microscope, nitrogen adsorption-desorption, Fourier transform infrared spectroscopy, and low voltage energy-dispersive X-ray spectroscopy. The catalytic activity was evaluated via the degradation of methylene blue in the presence of oxalic acid under UVA light and visible light. Immobilization of Fe2O3 on the perlite surface resulted in photo-Fenton catalytic activity for all samples, attributable to the formation of the hematite phase and the presence of surface Fe species. Owing to the low density of perlite, all catalysts float on the surface of the solution, which allows them to be easily separated.

Enhanced oxalate-induced degradation of organic dyes using magnetic photo-Fenton catalysts based on CuFe2O4-Fe2O3 composites

ABSTRACT The aim of this study was to synthesise magnetic CuFe2O4-Fe2O3 composite materials with enhanced photo-Fenton catalytic activity for the degradation of organic dyes in the presence of oxalic acid as radical-producing source. The composite catalysts were prepared by a simple hydroxide precipitation process followed by an annealing at 300°C with different annealing times. Their phase composition, morphology, surface atomic composition, surface functional groups and magnetic properties were characterised by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and vibrating sample magnetometry. The catalytic tests were carried out using methylene blue as a cationic dye and methyl orange as an anionic dye. According to the results, all CuFe2O4-Fe2O3 composite catalysts exhibited significantly higher photo-Fenton activities than CuFe2O4 sample under UVA light and visible light, which can be attributed to the enhanced content of Fe species and the high roughness observed on composite surface. These composite catalysts were found effective in degrading both cationic and anionic dyes although the decomposition of methyl orange was more difficult than that of methylene blue. Moreover, oxalic acid was also experimentally proved to be an excellent radical-producing source, which is superior to H2O2, in our photo-Fenton catalytic system. When the annealing time used in the synthetic procedure was extended, the catalytic performance of composite samples tended to increase but their magnetic properties were reduced, revealing that the annealing time is an important factor to be considered for the preparation of magnetic photo-Fenton composite catalysts.

In vitro evaluation of surface characteristics comparing WaterLase (Biolase®) with tungsten carbide burs for composite removal: a pilot study

Abstract Introduction The present ex-vivo study was designed to evaluate the surface roughness and analyse potential adhesive remnants on the enamel surface after composite removal using either an Er:YSGG WaterLase (WL) (Biolase®, Irvine, CA, USA) or a tungsten carbide (TC) bur (Alston, England, UK). Methods An in vitro study was designed using 21 extracted lower premolars. Pre-coated stainless steel brackets (3M Unitek, Monrovia, CA, USA) were bonded on all of the teeth except one, which served as a control. The teeth were allocated into two groups: Group 1 (n = 5), removal of composite with a TC bur. Group 2 (n = 15), removal of composite using the WL. Scanning electron microscope (SEM) imaging and Energy Dispersive X-ray Spectroscopy (EDS) were used to determine the surface roughness and atomic composition of the surfaces. Results Group 1 had a median damage depth of 17.6 µm with a range between 11.5 µ m and 28.7 µ m. Group 2 had a median damage depth of 166.3 µ m, with a range between 86.6 to 263.1 µ m. The depth differences between the two groups were statistically significant (p < 0.001, Mann–Whitney test). The atomic composition of the WL group was similar to sound enamel. The TC group showed a quantitative increase in carbon and silicone by 38.2% and 11.5%, respectively, a decrease in oxygen by 44.1% and an absence of phosphorous and calcium. Conclusion WL is efficient at removing composite from the enamel surface but could result in increased enamel surface roughness in comparison with conventional TC burs.

The effect of CO treatment on the surface structure of bimetallic Pd-Au/HOPG and Pd-In/HOPG nanoparticles: A comparative study

Bimetallic nanoparticles have been attracting more and more attention as catalysts in recent years since they often provide improved catalytic performance when compared to their monometallic analogues. Trying to design the optimum configuration of active sites in such catalytic systems, researchers resort to different strategies, one of which consists of a specific pretreatment of pre-synthesized nanoparticles in a particular gaseous environment prior to the catalytic reaction, resulting in adsorption-induced segregation. However, such a strategy does not always lead to any significant changes in the surface structure, so the identification of all factors responsible for the segregation process is of high fundamental and applied interest for the targeted design of bimetallic catalytically active nanoparticles. Here we show that for two types of bimetallic nanosystems, a stoichiometric intermetallic compound of Pd and In, and a substitutional solid solution of Pd and Au, the exposure to a CO atmosphere leads to completely different results, i.e., a noticeable surface segregation of Pd atoms being observed exclusively for the latter system. Driven by adsorption of CO molecules, the process of segregation is enhanced in the studied Pd-Au/HOPG catalyst (initial Pd/Au ratio of 1.48) when the temperature of the CO treatment is increased to 150 °C. In contrast, the Pd-In/HOPG nanoparticles (initial Pd/In ratio of 1.35) show no considerable change in the apparent surface atomic composition under a CO atmosphere, irrespective of temperature. Our results, alongside previous findings, demonstrate that CO adsorption-induced segregation as a tool for target-oriented modification of active sites in bimetallic nanoparticles for catalytic applications is appropriate only for substitutional solid solutions having a reasonable number of contacts between atoms of one type prone to segregation.

Highly branched gold-copper nanostructures for non-enzymatic specific detection of glucose and hydrogen peroxide.

The development of highly sensitive and highly selective sensors for non-enzymatic glucose and hydrogen peroxide (H2O2) detection using gold-copper alloy nanoparticles (AuCu alloy NPs) is reported. The AuCu NPs are nanostructures with branches and can be used as an electrochemical catalyst. Series of AuCu alloy NPs with various metal ratios are synthesized through acoreduction reaction. The morphology of AuCu alloy NPs is altered from highly branched structures (nanourchin, nanobramble, nanostar, nanocrystal) to a spherical shape by increasing Au content in the synthesis reaction. Cu-rich AuCu nanobramble and Au-rich AuCu nanostar exhibit selective electrocatalysis behaviors toward electro-oxidation of glucose and electroreduction of H2O2, respectively. The AuCu nanobramble-based sensor holds great potential in glucose detection with a linear working range of 0.25 to 10mM. The sensor possesses a sensitivity of 339.35μAmM-1cm-2, a limit of detection (LOD) of 16.62μM, which is an acceptable selectivity and good stability. In addition, the AuCu nanostar-based sensor shows excellent electrochemical responses toward H2O2 reduction with good selectivity, reproducibility, and a short response time of about 2-3s. The linear range for H2O2 determination is 0.05 to 10mM, with LOD and sensitivity of 10.93μM and 133.74μAmM-1cm-2, respectively. The good sensing performance is a result of the synergistic surface structure and atomic composition effects, which leads AuCu alloys to be a promising nanocatalyst for sensing both glucose and H2O2. Graphical abstract Schematic illustration presents the construction of gold-copper alloy nanoparticles (AuCu alloy NPs) on the surface of screen-printed carbon electrode (SPCE). The highly branched nanostructures of AuCu alloys with different surface structure and metal ratios give selective electrocatalysis behaviors. Cu-rich AuCu nanobramble-based sensor reveals prominent electrocatalytic activity for glucose detection. Au-rich AuCu nanostar-based sensor provides good electrochemical response for H2O2 detection.

Correlation between surface chemistry and morphology of PtCu and Pt nanoparticles during oxidation-reduction cycle

Process conditions during catalytic reactions induce significant changes in surface chemistry and structure of bi- (mono) metallic nanoparticles leading to their deactivation, and this can ultimately affect the reactions long-term performance. Here PtCu and Pt model nanoparticles are prepared by microwave synthesis and characterized by X-ray diffraction (XRD). Surface chemical and morphological changes of the nanoparticles during high-temperature oxidation and reduction treatments cycle are correlated by near in situ X-ray photoelectron spectroscopy (XPS) and ex situ transmission electron microscopy (TEM) - energy-dispersive X-ray spectroscopy (EDS) studies. At 300 °C the surface atomic composition of the PtCu nanoparticles switches reversibly upon the cycle and at the same time their morphology and composition are maintained. At 400 °C, the surface atomic composition does not fully restore and, while the shape is maintained, the size and composition are not. This occurs by a mechanism of Cu leaching out from the nanoparticles. These data delineate potential operating conditions for stable PtCu nanocatalysts.