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For achieving a sustainable energy future, energy consumption through renewable sources needs to be maximized and greenhouse emissions should be radically reduced. Automotive exhausts sharing the largest global NOX emissions must meet regulated standards by after-treatment systems (ATS) equipped with smart electronic feedback loops through on-board NOX monitoring. Herein, we demonstrate an efficient (Dy, W) co-doped Bi2O3-based electrochemical sensing architecture equipped with Ln2NiMnO6 double perovskite oxides (DPOs) as electrode materials for selective nitric oxides (NO) detection. The sensor configuration facilitates operation in a wide temperature range (325 °C–500 °C) with high sensitivity of 50 mV/decade, a response time below 60 sec. and detection abilities as low as 200 ppb. While investigating the impact of rare-Earth cations, a predominant Ni3+–O–Mn3+ interaction and acquisition of optimal eg 1 electron configuration of transition metal atoms in La2NiMnO6 was found responsible for improved electrocatalytic and redox chemical activity that substantiates the sensing behavior. The study carefully scrutinizes the sensing mechanism to abide by the mixed-potential model. Moreover, the durability assessed over a month of operation supported the applicability of presented sensing elements in on-board NOX monitoring systems.

This paper reports a systematic investigation of the radical scavenging behaviour of ceria with different morphological shapes inside Nafion membrane. All the ceria nanostructure is synthesized using a template-free hydrothermal route. Distinct crystal planes of CeO2 have different numbers of broken bonds and reaction sites having different surface energies. So, the preparation of CeO2 with various uncovered planes may enhance its scavenging activity. The crystal structure, morphology, and lattice structure are investigated using transmission electron microscopy (TEM), and x-ray diffraction (XRD). The results show that the radical scavenging efficiency of ceria strongly depends on the active surface plane, and decreases in the following order: nanorods > nanocube > nanosphere. Furthermore, the concentrations of surface oxygen vacancies and lattice cerium (III) are correlated with the morphology of the nanoparticles. This relationship clarifies the vital scavenging mechanism of CeO2 that mitigates degradation inside the polymer electrolyte membrane. This is because the inherent lattice strain on the active planes of nanosized ceria with different shapes affects their surficial reactions. The existence of prominent concentration of oxygen vacancy in the nanometric dimension of ceria leading to greater Ce3+ generation by exposed active phase CeO2 nanoparticles is key to achieve a durable hybrid Nafion membrane.

This work systematically investigates the oxygen nonstoichiometry, defect structure and mass/charge transport properties of Ba0.95La0.05FeO3−δ (BLF). Thermogravimetric measurement and coulometric titration were performed to determine change in oxygen nonstoichiometry (δ) with oxygen partial pressure ( P O 2 ) in 10−17 ≤ ( P O 2 /atm) ≤ 0.21 and 850 ≤ (T/°C)≤900 range. The δ− P O 2 −T plot showed “S-type” shape with a crossover plateau around δ ≈ 0.475. Defect modelling was used to explain the nonstoichiometry data and partial molar thermodynamic quantities for oxygen were determined. The DC 4-probe conductivity measurement was performed which showed a typical semiconductor-to-metal transition with temperature around the conductivity maxima at 450 °C. Electrical conductivity relaxation (ECR) measurement was performed to extract partial ionic conductivity, chemical diffusivity and surface exchange kinetics of oxygen ion by using Nernst-Einstein equation and Fick’s law. Isothermal chemical expansion was measured by dilatometry measurement in the range of 10−2 ≤ ( P O 2 /atm) ≤ 0.21 and 850 ≤ (T/°C) ≤ 950.

High temperature co-electrolysis of steam and CO2 based on solid oxide electrolysis cell (SOEC) to produce syngas as a feedstock for the well-known Fischer-Tropsch process is the main aim of the present research. Here Ni-8YSZ/8YSZ/LSCF6428-GDC button cells have been fabricated and the effect of the different microstructural parameters like air electrode thicknesses, fuel electrode porosities, adhesion layer and thermodynamic parameters like gas composition, temperature, on the performance of SOEC has been investigated systematically. The SOEC with 10 μm air electrode thickness, functional layer, fuel electrode having 20 vol% PMMA content, addition of YSZ-GDC adhesion layer gives the better performance in overall results and the voltage obtained for this SOEC at current density of 0.8 A.cm−2 is ~1.25 V at 800°C in 49% N2, 5% H2, 23% CO2 and 23% H2O gas mixture at fuel electrode side. To identify the electrochemical processes occurring at the electrodes of SOEC, distribution function of relaxation time (DRT) analysis of the electrochemical impedance (EIS) data is carried out.

The impedance of Ni-YSZ cermet electrodes was investigated as a function of different partial pressure of hydrogen and water. The impedance spectra for the hydrogen/water reaction show two reactions by DRT analysis. Reaction at high-frequency region was assigned to transport of electrode – oxidation reaction within the electrode structure and the electrode / electrolyte interface. Whereas low frequency response is the adsorption of a gaseous H2O molecule from the gas phase onto the active electrode site. The data are analyzed using an equivalent circuit representing two parallel RC. The values of activation overpotential are separated under the fixed current load, which are well-fitted to the Butler-Volmer equation. Under the current load, the variation of exchange current density ( ) with pO2 indicated that the total reaction-rate is determined by charge transfer reaction at the high temperature.

In recent years, the environmental friendly solid oxide fuel cell (SOFC) has been considered as one of the most efficient power generation systems. During the SOFC operation, the over potential is mainly given by the cathodic oxygen reduction reaction. In this respect, the mechanism of oxygen reduction on the Electrode is important to reveal. Specially, employing ac-impedance spectroscopy which provides an exceptionally is powerful tool for separating the dynamics of several electrode processes with different relaxation times. The present work considers the oxygen reduction reaction on the porous mixed conducting La0.1Sr0.9Co0.8Fe0.2O3-δ (LSCF1982) electrode by using ac-impedance spectroscopy. Firstly, to attain a mixed conducting state of LSCF1982, the ac-impedance spectra measured at various temperatures and oxygen partial pressures were quantitatively analyses by employing the theoretical impedance model developed for oxygen reduction on the mixed conducting electrode. All the measured impedance spectra simply consisted of two depressed arcs which overlapped slightly over the whole T and pO2 ranges. The analysis of the ac-impedance spectra by employing discrete Fourier relaxation transformation (DFRT) allowed us to successfully differentiate the individual reaction steps. This indicates that the overall cathode reaction proceeds by the following two processes: charge transfer reaction and subsequent migration of oxygen vacancy. It is also shown, that the magnitude of the high frequency arc decreased significantly with increasing T, but it remained nearly constant regardless of pO2: In contrast, the low-frequency arc remained almost unchanged in magnitude irrespective of the value of T, while it was highly dependent on the value of pO2. From the experimental results that it is thus deduced that the high frequency arc is attributed to the charge transfer reaction at the TPBs, and the low-frequency arc is associated with diffusion of adsorbed oxygen atom along the electrode/gas interface. Figure 1 shows the steady-state current of the oxide anodes as a function of the electrode potential and aO,int. According to Wang and Nowick [1], the rate determining step determined to exchange current density value as a function of both temperature and oxygen partial pressure. i0 ∝pO2 n The n - value in a relation gives information about the type of species involved in the electrode reaction. The n values have 1 if the rate limiting step is diffusional process of molecular oxygen, 1/2 for dissociative adsorption and 1/4 for charge transfer process depending on the conditions for Langmuir adsorption isotherm. In this study for LSCF1982, the slopes of current exchange density were turned out to be 1/4 at 550 to 650oC. This indicated that the rate limiting step for the electrochemical oxygen reduction in this temperature range is the charge transfer process. In the present work, the oxygen reduction reaction on the porous LSCF1982 electrode was examined by means of analysis of the ac-impedance spectra and DC polarization. In addition, we’ll discuss the other technic like cathodic potentiostatic current transients and Gerisher impedance modeling. Reference [1] Da. Yu. Wang and A. S. Nowick, J. Electochem. Soc., 126, 1155 (1979) Acknowledgement This work was supported by Solid Oxide Fuel Cell of New & Renewable Energy R&D Program (20123010030010) under the Korea Ministry of Knowledge Economy (MIKE)

Neodymium-doped ceria (Nd0.2Ce0.8O1.9, NDC)-based composite electrolytes with (Li/0.5Na)2CO3 have a higher conductivity than pure NDC in the intermediate temperature range (500-700°C). This may be attributed to protons that contributes to an improvement in the ionic conductivity across grain boundaries or phase interfaces, thereby providing conduction pathways between NDC and the carbonate material (interfacial super ionic conduction mechanism). In this research, the fundamental properties of the composite materials are characterized by a variety of experimental methods such as XRD, SEM, TEM, and TG-DSC. First, it is confirmed by XRD that the fluorite structure of ceria is maintained in the composite materials. Carbonates, which exist in form of an amorphous phase, as well as NDC particles, which have a cubic fluorite structure, are identified by SEM and TEM. A thermal analysis by TG-DSC is performed to determine the temperature at which the binary eutectic of (Li/Na)-carbonate is formed. Electrical conductivities of composite electrolytes are also analyzed by EIS at 250-650 °C in air atmosphere.

The proton conducting electrolyte cerium pyrophosphate was synthesized by digesting cerium oxide with 85% H3PO4. The crystal structure and phase stability of the material were analyzed by X-ray diffraction and thermogravimetric analysis/differential thermal analysis (TGA/DTA), and the microstructure was analyzed by scanning electron microscopy (SEM). The electric conductivity behavior of CeP2O7 sintered pellets was analyzed by electrochemical impedance spectroscopy (EIS) and modulus spectroscopy. The activation energies for migration (Eω) and dc conduction (Eσ) calculations indicates that the charge carriers responsible for conductivity and relaxation are same and the concentration of charge carries is independent of temperature. The variation of conductivity with temperature was studied in dry and humid atmosphere for the possible application as electrolyte in proton conducting ceramic electrolyte fuel cells (PCFCs) in the temperature range of 100–220 ◦ C, which showed that the conductivity of CeP2O7 was mainly due to the incorporation of water and the maximum conductivity was found to be 2.1 × 10 −4 Sc m −1 at 175 ◦ C and PH2O = 0.06 atm. The presence of water in CeP2O7 matrix increases the number of jump sites and facilitates the hopping of protons, leading to an increase in the conductivity.

Partial electronic conductivity and total conductivity of Zr0.84Y0.16O1.92 and Ce0.9Gd0.1O1.95 have been measured by Hebb-Wagner polarization method and D.C. 4-probe conductivity measurements, respectively as a function of temperature and oxygen partial pressure. (600 ≤ temp/˚C ≤ 900, 10-18 ≤ PO 2/atm ≤ 0.21) Theoretical current-voltage characteristics and power density were calculated by integrating partial conductivities of charge carriers under various DC bias condition at fixed oxygen chemical potential gradient at both sides of the electrolyte (YSZ side: PO 2=10-22 GDC side: PO 2=0.21). The spatial distribution of oxygen partial pressure across the bilayer electrolyte with various thickness ratio was calculated based on Choudhury and Patterson’s model by considering zero electrode polarization. From the spatial distribution, oxygen partial pressures of interface were calculated with various operating condition. Interfacial oxygen chemical potential with various thickness ratio (YSZ/GDC) shows strong dependence upon cell operating potential.

Impregnation or infiltration are terms used to describe the process of depositing nano particles into electrode structure. Using infiltration of nano particles, cell performance can be improved due to increased three phase boundary (TPB) where electrochemical reactions occur. So, by infiltration of dispersed particles, we can expect more performance due to increased surface area. But, many literatures related to infiltration for improving performance deal with almost air electrode infiltration. Commonly, Ni and electrolyte materials are used as fuel electrode. To infiltrate nano particles, fuel electrode needs appropriate porosity and maintains porous structure. But, it is hard for fuel side electrode to maintain its structure because Ni can be oxidized to NiO easily during heat treatments. So, not to be reoxidized, reduction of fuel electrode was done at the last process. And, one side reduction is necessary because air electrode can be decomposed in low pO2 condition. To infiltrate dispersed nano particles, we used urea precipitation method because it gives the solution precipitating ligands to whole solution so that precipitations occur homogeneously. Because urea needs decomposition time, urea concentration should be higher than cation concentration so as to precipitate whole cations. Thus, urea/cation concentration ratio and aging time were chosen as variables. Infiltration was conducted to Ni-YSZ support whose air electrode side was blocked by epoxy. After infiltration, epoxy was burned out at 600oC with fuel electrode flowed by H2. Finally, electrochemical properties were investigated by I-V curve, EIS and DRT.

Mixed oxide-ion and electron conducting ceramic material La2NiO4+ d (LNO) have been reported to exhibit impressive oxide ion and p-type electronic conductivity, and high catalytic activity which makes them an excellent component of some electrochemical devices such as fuel cell cathode, oxygen permeation membrane and sensors. The structure of hyper-stoichiometric LNO is consists of alternating LaNiO3 perovskite and LaO rock salt layers. The oxygen excess in LNO is associated with the incorporation of interstitial oxygen into the rock salt layers and holes are simultaneously created in the perovskite layers to maintain the charge neutrality of the system. Given the oxygen activity difference across an oxide, its electrochemistry is determined by its ambipolar conductivity or the product of its oxide ionic conductivity and electronic transference number or vice versa. The partial ionic and electronic conductivities which govern the mass transport in an electric field are thus the most important properties of an electrochemical device material to characterize and understand. However, there are very few reports on the study of transport properties of mixed conducting oxide material. In this work we have analyzed the partial conductivity of La2Ni0.95Al0.05O4.025+ d in relation with the thermoelectric power and calculate diffusion coefficient and surface exchange coefficient in order to analyze the oxygen exchange kinetics of La2Ni0.95Al0.05O4.025+ d.

The most widely studied anode for oxidation of hydrogen in solid oxide fuel cells (SOFCs) is the Ni/YSZ cermet. A detailed understanding of the rate-limiting steps in Ni-YSZ anodes is highly desirable from an optimization point of view. One of the most promising way of complex system is to define the reaction by impedance spectroscopy. In principal, impedance measurement is comprised of electrolyte response, electrode response, and transport limitations for supply of reactants and removal of products. The electrolyte response is readily separated out as a series resistance, in simple geometries it can even be used to indicate the magnitude of the microscopic electrode contact area. For high temperature impedance model, transport restriction are believed to be negligible in typical setups. But anode with low resistance transport restrictions may contributes significantly. The electrode reactions like charge-transfer reaction are suggested to occur in the vicinity of the active triple-phase boundary (TPB) line. The active TPB is defined as the line where the Ni network, the YSZ network, and open pores meet to form percolation paths for transport of electrons, oxide ions, and gas respectively. The reaction resistance related to any process occurring across the active TPB is coupled in parallel between Ni and YSZ. This paper (i) brings forth a method of rationalizing impedance data and (ii) presents relevant data for the oxidation of hydrogen on Ni/YSZ cermet anodes produced by tape casting. In the analysis of the obtained impedance spectra, the distribution of relaxation times (DRT) was calculated in order to perform a pre-identification of the physico-chemical processes occurring in the cell. The impedance data are rationalized by fitting to a representative equivalent circuit, thus allowing the dependency of three processes on typical parameters to be derived.

Some perovskite-type oxides have shown high proton conductivity in wet hydrogen atmosphere. In these perovskite oxides the partial substitution of an acceptor dopant for B-site results in formation of oxygen vacancies, which lead to the formation of protonic defects by the absorption of water in wet atmosphere. Among various proton conducting perovskite-type oxides, Y-doped Barium cerate and barium zirconate are nearly isomorphic. Therefore, the basic phases of a binary solid solution where B-sites are randomly occupied by either Zr4+ or Ce4+. This is because the chemical instability of Y-doped BaCeO3- δ in the presence of CO2-, H2O- or SO2-containing atmosphere below 973K was substantially improved by replacing Ce with Zr to form a solid solution, and the mechanical strength was also enhanced when the proton conductivity and thermal stability remained adequate over a wide range of operation conditions for the fuel cell. To elucidate the transport properties and defect structure of a Ce/Zr-coexisting preovskite structure, BZCY(BaZrxCe1-xY0.15O3- δ, x=0, 0.2, 0.4, 0.6) was chosen as the model system. First, we study the electrical properties of BZCY in various oxygen and water vapor atmospheres by four-probe DC measurements as a function of temperature. And then, these properties are analyzed analytically, based on the defect structure of the material. Furthermore, we use the conductivity relaxation measurement technique to monitor the monotonic/non-monotonic(two-fold) relaxation for the BZCY under various themodynamic conditions and extract the chemical diffusivities by solving Fick’s second law for each case on the basis of hydrogen- and oxygen- decoupled diffusion as proposed by Professor Yoo1-3. Fig. 1 shows the typical relaxation profiles of the mean total conductivity upon oxidation and reduction across an identical oxygen activity window. During the redox reaction driven by the oxygen chemical potential gradient at a fixed water vapor activity, oxygen may be incorporated into the BZCY by ambipolar diffusion of V•• o and 2h• in the p-type oxidizing regime. In Fig. 2, conductivity relaxation profiles upon hydration and dehydration at a fixed pO2(≈0.21 atm) are shown as a function of water vapor activities at 1023K. The figures clearly reveal the violation of monotonic relaxation governed by the chemical diffusion of water, according to the ambipolar diffusion of oxygen vacancies and proton. As shown in the fig. 2, non-monotonic twofold relaxation behavior was clearly observed for the BCZY system. 1. H.I. Yoo et al., Phys Chem Chem Phys, 10, 974 (2008) 2. H.I. Yoo et al., Solid State Ionics, 180, 1443 (2009) 3. J.I. Yeon et al., Solid State Ionics, 181, 1323 (2010) 4. S. Hamakawa et al., Solid State Ionics, 148, 71 (2002) 5. S.-J. Song et al., Solid State Ionics, 167, 99 (2004) 6. S.M. Haile et al., Nature, 125, 271 (1999) 7. D. Pergolesi et al., Nature Materials, 9, 846 (2010) 8. H. Iwahara et al., Solid State Ionics, 125, 271 (1999) 9. Y.C. Yang et al., Sensors and Actuators B, 140, 273 (2009) 10. C. Zuo et al., Advanced Materials, 18, 3318 (2006).

Mixed oxide-ion and electron conducting ceramic material La2NiO4+ d(LNO) have been reported to exhibit impressive oxide ion and p-type electronic conductivity, and high catalytic activity which make them an excellent component of some electrochemical devices such as fuel cell cathode, oxygen permeation membrane. The hyperstoichiometric LNO oxides show high oxygen diffusion coefficient and high oxygen ion conductivity, which are attributes of their crystal structure. The extent of oxygen nonstoichiometry significantly affects the electrochemical properties of LNO systems. The nonstoichiometric oxygen content may be varied by aliovalent doping or by substituting the host cation with smaller size cations[1,2]. The conduction mechanism in LNO-based system has been explained on the basis of both, the band conduction by delocalized electrons and polaron-hopping by localized electrons[3,4]. The objective of this work is to study the effect of a donor cation (Al3+) on oxygen nonstoichiometry and resultant thermodynamic properties of LNO system. In this work we have prepared a non-transition metal cation Al3+-doped LNO system, La2Ni0.95Al0.05O4.025+ d, and presented an equilibrium defect model for this system. The variation of oxygen nonstoichiometry was measured by coulometric titration and the absolute value of oxygen nonstoichiometry was calculated from thermogravimetric analysis. Various thermodynamic quantities for LNAO were calculated from the experimental data and were compared with those for LNO in our previous work. Fig.1 shows pO2 dependence of oxygen nonstoichiometry at different temperature. As can be seen, the values of δ increased with decreasing temperature and with increasing pO2. The inset of Fig. 1 shows the relationship of log δ vs. log pO2, as can be seen, at isothermal condition the dependence of δ on the pO2exponent (m) is slightly less than 1/6. It is clear from the above observation that the oxygen exponent decreases with increasing oxygen activity, suggesting a positive deviation of the LNAO system from the ideal solution behavior[4]. The best estimated values of Nv obtained from fitting the Eq. (1) with fitting parameters Kox, Kf, and Nv to the δ vs. log(pO2) data in Fig.(1). The density of states of the valence band varies from 1.87x1020 to 2.55x1020 in 800-1000 oC range. And , the effective mass mh *of holes is 1.02 - 1.21 times the rest mass mo. This indicates the occurrence of band-like conduction and allows the effect of conduction by a small degree of polaron hopping to be ignored. The behavior of holes starts deviates from that of ideal solution at a very low δ value and rh • increases with the increasing δ and reaches to ~7 at rh •≈0.08 and T=900°C. The calculation of excess partial molar quantities showed that incorporation of interstitial oxygen is less favorable in La2Ni0.95Al0.05O4.025 + δ in comparison to La2NiO4 + δ. Reference Nakamura T, Yashiro K, Sato K, Mizusaki, J. Solid State Ionics, 180, 368 (2009). Naumovich EN, Patrakeev MV, Kharton VV, Yaremchenko AA, Logvinovich DI, Marques FMB. Solid State Sciences, 7,1353 (2005). H. S. Kim, and H. I. Yoo, Solid State Ionics, 232, 129 (2013). H. S. Kim, and H. I. Yoo, Phys. Chem. Chem. Phys., 12, 4704 (2010).

Cerium pyrophosphate based solid state proton conducting materials with ionic conductivity >10-2 S cm-1 in 100-250 oC range have immense importance in fuel cells.1-5 In this work, Ce1-xMnxP2O7 (CMP) (x=0.05, 0.075, 0.1, 0.125 and 0.15) composite electrolytes are synthesized by two-step slow digestion method with different P/(Ce+Mn) molar ratio.4 The CMP samples with high phosphate content become denser on sintering. The variation of ionic conductivity with temperature is studied in dry and humidified air for the potential application of CMPs as electrolytes in proton-conducting ceramic electrolyte fuel cells. Among various CMP samples, CMP-100-2.7P (i.e. Ce0.9Mn0.1P2O7 with P/(Ce+Mn)=2.7) shows maximum conductivity of 6.54X10-6 S cm-1 at 450 oC in dry air and 1.78X10-2 S cm-1 at 170 oC in humidified air (pH2O= 0.12 atm). The ionic conductivity of CMPs increases with the increasing pH2O and CMP-100-2.7P shows maximum conductivity of 2.24X10-2 S cm-1 at 170 oC in pH2O=0.16 atm. Figure. (a) SEM images of fractured section of 400 oC sintered pellets of Ce0.9Mn0.1P2O7 samples with different initial P/(Ce+Mn) ratio; Temperature dependence of ionic conductivity of various CMP samples with different dopant concentration in (b) dry air and (c) humidified air (pH2O =0.12 atm) condition. References B. Singh, H. N. Im, J. Y. Park, and S. J. Song, J. Electrochem. Soc., 159, F819 (2012). B. Singh, H. N. Im, J. Y. Park, and S. J. Song, J. Phys. Chem. C, 117,2653 (2013). B. Singh, H. N. Im, J. Y. Park, and S. J. Song, J. Alloys Compd., 578, 279 (2013). B. Singh, S. Y. Jeon, J. H. Kim, J. Y. Park, and S. J. Song, (Submitted in J. Electrochem. Soc.). C. Chatzichristodoulou, J. Hallinder, A. Lapina, P. Holtappels, and M. Mogensen, J. Electrochem. Soc., 160, F798 (2013).

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The electrical conductivity, Seebeck coefficient, and thermal chemical expansion properties of La 2 NiO 4+δ were measured as a function of temperature and oxygen partial pressure (pO 2 ). The electronic conductivity was analyzed in relation to the thermoelectric power (thermopower) data to elucidate the positive deviation of the activity coefficient of hole on the basis of the delocalized electron model by using the Joyce-Dixon approximation of the Fermi-Dirac integral from the partition function in the quasi-free-particle approximation with the regular solution model. The electrical conductivity and thermopower vs oxygen activity were all explained consistently in the logical frame of the degenerate p-type conductor across the entire experimental range investigated. Like other K 2 NiF 4 -type oxides, the chemical diffusion coefficient was slightly higher than the surface exchange coefficient, suggesting the need for further work to enhance the sluggish surface exchange kinetics of oxygen. The best-estimated mobility values were in reasonable agreement with the reported values and the very weak temperature dependence of hole mobility suggested a band conduction.

The thermal and chemical expansion properties of BaCo 0.7 Fe 0.22 Nb 0.08 O 3-δ , a potential candidate for oxygen permeable membranes and cathodes in solid oxide fuel cells, are reported here. The average thermal expansion coefficient is about 14 × 10- 6 K -1 below 500°C, about 19 × 10- 6 K -1 between 600 and 900°C, and about 29 × 10- 6 K -1 between 900 and 1000°C, which consists of the previous weight change in a thermal gravimetric analysis experiment. The transient behavior in the thermochemical expansion can be best fitted with Fick's second law for a small displacement from the equilibrium. The chemical diffusivity of oxygen and the surface exchange kinetics are successfully extracted.

A solid solution of Pd-Ag nanoparticles was synthesized by the conventional polyol process. Silver nitrate (AgNO 3 , Aldrich), palladium(II) nitrate hydrate [Pd(NO 3 ) 2 ·xH 2 O, Aldrich], and ethylene glycol were used as the starting materials. Ethylene glycol was used as the surfactant for the solvent and reductant. Water was used to ensure that the reduction potentials of the two metals remained very similar in the aqueous solution. The obtained alloy nanopowder sample was characterized by X-ray diffraction (XRD). The obtained XRD pattern was refined using the Full-Prof program according to the Rietveld method and the mean crystallite sizes were estimated using the Scherrer equation. The quantitative atomic percentage across the nanoparticles was determined by using scanning transmission electron microscopy images to confirm the formation of the Pd/Ag alloy nanopowder.

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