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Abstract: Ag nanocubes that are 45nm in size are synthesized and successfully used as catalysts in oxygen electroreduction. Electrochemical surface areas (ESAs) are considered to determine the effect on HO2 − production, which is found to be in the following order: nanocubes

Abstract: Palladium nanocubes (27, 48, and 63 nm) composed of (100) planes were successfully synthesized for use in oxygen electroreduction in 1-M NaOH electrolyte. The results (at −0.1 V vs. Ag/AgCl) of a rotating ring-disk electrode measurement showed that the specific activities of the 27-, 48-, and 63-nm Pd nanocubes were 3.05 × 10−2, 3.41 × 10−2, and 2.44 × 10−2 mA cm−2, respectively. 48 nm Pd nanocubes exhibited the higher activity than larger nanocubes and 9 nm Pd nanoparticles, where the specific activity of nanoparticles was 2.16 × 10−2 mA cm−2. [Copyright &y& Elsevier]

Abstract: A facile synthesis method has been developed for preparing porous hexadecyltrimethylammonium-coated Pt–Ag nanosponges using ascorbic acid. As determined via electron diffraction and mapping element measurements, the nanosponges feature fcc and mixed-alloy structures. The nanosponges were successfully deposited on the sidewalls of sodium dodecyl sulfate-micelle-functionalized herringbone graphite nanofibers (Pt–Ag/GN) using an electrostatic attraction. Further, as supported by in situ analyses, the mass activity and electrochemical kinetics of the Pt–Ag/GN nanocomposite toward the electrocatalysis of the oxygen reduction reaction (ORR) were studied. The results demonstrate that the mass activity of Pt–Ag/GN is 5.59 × 10−3 mA μgpt −1 and greater than 3.91 × 10−3 mA μgpt −1, the commercial Pt/C (at −0.15 V vs. Ag/AgCl). The numbers of ORR transfer electrons on the new composites reached 3.44 (at −0.15 V vs. Ag/AgCl), which shows that the ORR occurred quickly. [Copyright &y& Elsevier]

Abstract: Porous triangular Ag/Pd nanoplates with different alloy ratios, including Ag18Pd1, Ag18Pd1.5, and Ag18Pd2, were successfully prepared by a galvanic displacement reaction. These alloy nanoplates were then used as methanol-tolerant electrocatalysts in an alkaline oxygen reduction reaction (ORR). Electrochemical measurements were conducted using an ultrathin film rotating ring-disk electrode. The mass activity was found to decrease in the order Ag18Pd1 > Ag18Pd2 > Ag18Pd1.5 > Pt nanoparticles > Pd nanoparticles, similar to an observation made in a past analysis of the nanoplates in an electrolyte of free methanol; this indicates that these nanoplate catalysts are more economical than Pd nanoparticles, and even Pt nanoparticles. Additionally, compared to the reactive direction in the case of Pt and Pd nanoparticles toward methanol oxidation in an ORR electrolyte with methanol, all Ag/Pd nanoplate catalysts experienced cathodic currents, which indicate that ORRs occurred even in the presence of methanol. Despite working in a methanol-tolerant solution, the prepared alloy nanoplates still exhibited high electroactivity. [Copyright &y& Elsevier]

Abstract: A novel method for the synthesis of as-prepared Ag nanoplates in high yield and the control of their dimensions has been developed. In this method, hexadecyltrimethyl ammonium ions (CTA+) are used as a trace additive in a seed solution for blocking the seed surface to govern the growth direction on nanoplate in the growth pathway, leading to a high-yield production of the Ag nanoplates with mixed morphologies, mainly triangular nanoplates and nanodisks. The spectra of the obtained nanoplate solution showed a high-intensity peak attributed to the in-plane dipole resonance and a low-intensity peak at 400 nm. By decreasing the amount of CTA+, the mean edge length of triangular nanoplates could be changed from ∼78.7 nm–∼124.8 nm. The in-plane dipole resonance peak corresponding to change in the mean edge length shifted from 630 nm to 785 nm, respectively. The mean edge length of triangular nanoplates could also be controlled from 70 nm to 148 nm by decreasing the CTA+-adsorbed seed amount. To investigate the practical feasibility of application of the proposed method, the prepared nanoplates were used as a methanol-tolerant electrocatalyst in an oxygen reduction reaction (ORR). An analysis conducted using a rotating ring-disk electrode showed that these nanoplates have high activity towards the ORR and that the electron transfer numbers (n) were 3.85, 3.83, 3.81, and 2.94 for 70 nm, 124 nm, 148 nm nanoplates, and macroscopic Ag electrode, respectively. If the present of methanol, the corresponding n values of 3.82, 3.81, 3.78, and 2.30 were detected. Despite working in the methanol-tolerant solution, the prepared Ag nanoplates still exhibited high electroactivity and their ORR proceeded via an approaching 4-electron pathway. [Copyright &y& Elsevier]

Abstract: Mesoporous Pt nanosponges of high activity were successfully synthesized for the oxygen reduction reaction (ORR). These porous nanosponges of 48.7, 53.7, 62.8, and 77 nm in size were synthesized by changing the concentration of polyvinylpyrrolidone electrolyte in the electrochemical synthesis. The electrochemically active surface areas (EASs) of the 48.7-, 53.7-, 62.8-, and 77-nm Pt nanosponges used toward H-adsorption and H-desorption were 162.84, 137.76, 116.71, and 103.83 m2/g, respectively. These measured EASs of these nanosponges were larger than the EAS contributed by the Pt nanoparticles of 76.69 m2/g. As for the ORR, electrochemical measurement and Koutecky–Levich plots showed that the kinetic current densities catalyzed by the 48.7-, 53.7-, 62.8-, and 77-nm Pt nanosponges at 0.7 V (vs. Ag/AgCl) were 0.488, 0.483, 0.450, and 0.370 mA cm−2, respectively; and the 48.7-nm Pt nanosponges had high reducing activity in the ORR. A size-dependent activity was found. As a reveal of the results of a rotating ring-disk electrode experiment, the catalysis of the ORR by the 48.7-nm Pt nanosponges occurred through the 4-electron pathway, and the efficiency of H2O production was approximately 99.4%. [Copyright &y& Elsevier]

Abstract: Ag–Pd nanoparticles with compositional ratios of 1:1 (Ag1Pd1), 2:1 (Ag2Pd1), and 4:1 (Ag4Pd1) and supported on multiwall carbon nanotubes (CNTs) were prepared by the self-regulated reduction of sodium dodecyl sulfate, and then, they were used as catalysts for oxygen reduction reactions (ORRs) in 1 M NaOH solution. Polarization curves showed that, among the prepared nanocatalysts, Ag4Pd1/CNT nanocatalysts showed higher activity. During the ORRs, two types of oxygen coverages given by the Temkin isotherm and Langmuir isotherm were observed for low and high overpotentials, respectively. Koutecky–Levich plots showed that the number of electrons involved in the ORRs catalyzed by Ag1Pd1/CNT, Ag2Pd1/CNT, and Ag4Pd1/CNT were 2.11, 1.88, and 2.25, respectively. These ORRs proceeded through a two-electron pathway. Polarization curve in the electrolyte with methanol revealed that Ag4Pd1/CNT has high methanol tolerance during ORRs. [Copyright &y& Elsevier]

Abstract: Triangular Ag nanoplates with large and small sizes were successfully synthesized for oxygen electroreduction. From the results of the x-ray diffraction analysis, it was concluded that Ag nanoplates of small size are the crystals that are essentially composed of (111) planes. The data provided by electrochemical measurement and the Koutecky–Levich equation showed that the electron numbers involved in the oxygen reduction reaction of small and large Ag nanoplates are 3.27 and 3.16, respectively. Small Ag nanoplates exhibit maximum activity towards the oxygen reduction reaction. [ABSTRACT FROM AUTHOR]

• Syntheses of dGNs with vacancy defects, dGN ht , and N-, B-, S-, and Fe-doped dGNs are demonstrated. • Sequential and transient catalysis of HPRR by these dGNs are studied. • dGN with N and O atom as electron donnor had greater specific activity than dGN with B, Fe, and S. • Physical adsorption of H 2 O 2 on the dGNs in the mechanism limits HPRR. The activities in the sequential and transient electrocatalysis of hydrogen peroxide reduction reaction (HPRR) of defective graphene nanosheet (dGN) were studied along with dGN without dopant obtained by hydrothermal reaction (dGN ht), and N-, B-, S-, and Fe-doped dGNs. dGNs with 5−7-7−5 vacancy, 5–9, and point defects were successfully prepared by a green and sonoelectrochemical system, two graphite electrodes, and phosphate buffer electrolyte. The results showed that the specific activities in terms of electrochemical surface areas for dGN with N and O atom as the electron acceptor for C atom were greater than those of dGN B, S, and Fe atom as the electron donor. The weak activity by S-doped dGN could be attributed to the low bond polarity between C and S atom. The physical adsorption of hydrogen peroxide on the carbon catalysts limited the reaction kinetics. The amperometric curves of transient catalysis at −0.4 V vs. Ag/AgCl revealed that the reductive currents of the tested catalysts for sensing H 2 O 2 follow the order: N-doped dGN > Fe-doped dGN > B-doped dGN > dGN ht > S-doped dGN > dGN. [ABSTRACT FROM AUTHOR]

Palladium octahedrons (Octs), nanocubes (NCs), and rhombic dodecahedrons (Rds) bounded by (111), (100), and (110) planes, respectively, were synthesized and used as catalysts for the D-glucose oxidation reaction (GOR) in alkaline media. The specific activities of these catalysts were systematically studied to assess their performance under sequential and transient conditions. For sequential oxidation (supposedly leading to gluconolactone formation) driven by cyclic voltammetry, the activity followed the order NCs >> Octs > Rds, attributable to the preferential binding of OH − to the (100) plane. Furthermore, cyclic voltammetry tests indicated high D-glucose tolerance of the catalysts and the dependence of their stability on the bounding crystalline planes. For catalysis under transient conditions at an applied fixed potential (−0.05 V vs. Ag/AgCl (3 M KCl)), Octs showed a higher current density response upon the addition of D-glucose than did NCs. However, the above response for Octs decreased upon the addition of uric acid. Comparative electrochemical analysis showed that NCs show better activity, sensitivity, and a lower D-glucose detection limit than the other nanocatalysts, and are thus the most suitable for the GOR. [ABSTRACT FROM AUTHOR]

Pd nanocubes enclosed by (1 0 0) planes are successfully used as stable catalysts for d -glucose sensors. In this study, a comparison of the specific activities in terms of electrochemical real surface area (ESA) between the Pd nanocubes enclosed by (1 0 0) planes and Pd nanoparticles dominated by (1 1 1) planes is performed to assess their ability to electrocatalyse glucose oxidation. By measuring activity per ESA, the nanocubes (6.3 × 10 −5 C cm −2 ) are found to perform 1.45 times better than the nanoparticles (4.32 × 10 −5 C cm −2 ). The higher specific activity of the nanocubes can be attributed to the higher oxidation power of the anodic glucose oxidation process catalysed by the (1 0 0) planes of the nanocubes. Furthermore, the prepared nanocubes show great potential and stability for use as a glucose sensor system as they have a sensitivity of 34 μA mM −1 cm −2 and a linear range of 1–10 mM. [ABSTRACT FROM AUTHOR]

• Syntheses of Pd@Pt Oct , Pd@Pt RD , and Pd@Pt NC are successfully demonstrated. • Sequential and transient catalysis of GORs by three Pd@Pt particles are studied. • GORs on the Pd@Pt Oct and Pd@Pt NC proceed via a one-electron pathway. • GOR on Pd@Pt RD occurs via a two-electron mechanism. • Pd@Pt Oct and Pd@Pt RD had slightly higher activity than Pd@Pt NC. Sequential and transient electrocatalysis of d- glucose oxidation reactions (GORs) were studied using core-shell Pd@Pt particles with octahedral (Pd@Pt Oct , 76.2 nm), rhombic dodecahedral (Pd@Pt RD , 79.3 nm), and nanocubic (Pd@Pt NC , 62.7 nm) geometries to determine the reaction mechanism. The resulting currents and in situ frequency changes, measured using an electrochemical quartz crystal microbalance, clearly revealed that the molar ratios of electron to d- glucose mass were 1.24 and 1.22 for the sequential catalysis of the glucose oxidation by Pd@Pt Oct and Pd@Pt NC , respectively; however, a higher ratio of 2.22 was observed for Pd@Pt RD. The GORs catalyzed by Pd@Pt Oct and Pd@Pt NC occurred via a one-electron pathway to produce gluconate, whereas the GOR catalyzed by Pd@Pt RD occurred via a two-electron mechanism to generate δ-gluconolactone. A comparison based on the same electrochemical surface areas suggested that Pd@Pt Oct and Pd@Pt RD have slightly higher activities than that of Pd@Pt NC. The amperometric curves of transient catalysis at −0.05 V vs. Ag/AgCl revealed that the oxidative current density of the tested catalysts after 200 s follow the order of Pd@Pt Oct > Pd@Pt NC > Pd@Pt RD. [ABSTRACT FROM AUTHOR]