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Summary: Catalyst support alters the electronic structure of metal catalysts, resulting in an enhanced activity. In this study, nitrogen‐doped defective graphene nanosheet‐supported Pt nanoparticles (2.8 nm) (Pt/N‐dGN) were prepared and successfully used as electrocatalysts in the sequential and transient catalysis of the neutral d‐glucose oxidation reaction (GOR). The Pt nanoparticles were determined to be single crystals enclosed with the (110) plane. The spherical‐aberration‐corrected field transmission electron microscopy image revealed a Pt/N‐dGN bearing with point vacancies, 5‐8‐5, 5‐9, and 5‐7‐7‐5 defects. N‐dGN was prepared by fast exfoliation and sequential nitrogen doping with urea using a sonoelectrochemical and hydrothermal method. The Pt/N‐dGN with a Pt binding energy of 71.4 eV showed significant mass activity (7.83 × 1019 molecules g−1Pt) toward the sequential catalysis of neutral GOR. The electron transfer number was 2.71 and approximately two‐electron transfer mechanisms occurred. The repeated currents of GORs were observed in the catalysis from the 2nd cycle to the 25th cycle. [ABSTRACT FROM AUTHOR]

Abstract: Tetradecyltrimethyl ammonium ions (C14TA+) were used as trace additives in a seed solution to block the (111) seed surface so as to govern the growth direction and pathway, leading to the formation of Ag nanoplates. 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 400nm. By decreasing the amount of C14TA+-adsorbed seed amount from 20μL to 15μL and 5μL the mean height of triangular nanoplates was altered from ∼96nm to ∼130nm and ∼177nm. The in-plane dipole resonance peak, which corresponds to the change in the mean height, shifted from 655nm to 740nm and 807nm, respectively. To investigate the feasibility of practical application of the proposed method, the prepared nanoplates were used as an electrocatalyst to sense a glucose oxidation reaction (GOR). A cyclic voltammogram of the nanoplates showed two significant peaks during the cathodic sweep, indicating that the anodic oxides provide active sites and have high GOR activity. Simultaneously, the results measured by potential deposition of Pb show the nanoplates have electrochemical surface areas (ESAs) of 96nm>130nm>177nm. The higher activity on the 96nm sized nanoplates is attributed to the fact they have the largest ESA. Remarkably, the prepared nanoplates show high potential as glucose sensors, in that the 96nm nanoplates showed 0.527mAmM−1 cm−2 sensitivity for glucose. [Copyright &y& Elsevier]

• Specific activities of RD, OCT, and NC Cu 2 O catalysts upon GORs are studied. • RD shows greater specific activity than OCT and NC. • RD catalyst shows an early rest potential of −0.228 V. • GOR on RD has lower activation energy than those on OCT and NC. • GORs on the three catalysts proceed via a two-electron pathway. The specific properties, in terms of real surface area (RSA), of (1 1 0)-faceted rhombic dodecahedral (RD), (1 1 1)-faceted octahedral (OCT), and (1 0 0)-faceted nanocube (NC) Cu 2 O crystals as D-glucose oxidation catalysts were studied. Tafel measurements showed the activation energy of the RD catalyst (65.4 KJ mol−1) was lower than the energies of the OCT and NC catalysts (91.8 and 97.4 KJ mol−1, respectively). Due to the facile surface oxidation of CuO, the RD catalyst showed an early rest potential of −0.228 V (vs. Ag/AgCl, 3 M KCl), and had a much higher specific activity (0.253 mA cm−2) at 0.6 V compared to the OCT and NC catalysts (0.11 and 0.09 mA cm−2, respectively). The glucose oxidation reaction (GOR) catalyzed by the RD crystals occurred via a two-electron mechanism, in which δ-gluconolactone was formed. Amperometric measurements provided a fixed 0.6 V value, showing high sensitivity (87.97 μA mM−1· c m RSA - 2 ) within a linear analysis range of 0.1–8.4 mM. The high activity of the RD catalyst may originate from the coexistence of oxygen and cuprous ions on its outer plane, and its facile surface oxidation to CuO. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Pd@Pt CINPs are successfully synthesised through a seed-growth method. • Pd@Pt CINPs are successfully as electrocatalysts for GOR in PB solutions. • The mechanism and kinetics of GOR are monitored and studied using EQCM. • 12.9 nm Pd@Pt CINPs provide greater activity than 9 nm Pt nanoparticles. Abstract Concave Pd core/ island Pt shell nanoparticles (Pd@Pt CINPs) were successfully synthesised and used as catalysts for the glucose oxidation reaction (GOR) and to directly sense D-glucose in phosphate-buffered solutions. The results measured by an electrochemical quartz crystal microbalance (EQCM) indicate that the GOR accelerates from -0.3 V (vs. Ag/AgCl) to 0.2 V and at least 1.0067 μg of glucose reacted with the Pd@Pt CINPs for each catalysis. A favourable comparison shows that 12.9 nm Pd@Pt CINPs have high sensitivity (15.14 μAmM−1 cm-2), which is four times greater than the 3.7 μAmM−1 cm-2 of 9 nm Pt NPs. The greater sensitivity within a linear range of 1–8.5 mM and high stability during repeated GORs indicate that Pd@Pt CINPs are potential non-enzymatic glucose sensors. [ABSTRACT FROM AUTHOR]

[Display omitted] • Core-shell PdAu Oct, t -Oct, and NC are successfully prepared. • Specific activities of these PdAu nanocrystals as glucose sensors are studied. • The GOR kinetics on these PdAu nanocrystals are studied using EQCM. • PdAu t -Oct with (2 1 1) planes is the best catalyst for bonding with glucose. • Facile electron transfer of GOR occurs on the PdAu Oct. Core-shell PdAu octahedrons (Oct), PdAu truncated octahedrons (t -Oct), and PdAu nanocubes (NC) were successfully synthesised, and their specific activities, in terms of electrochemical surface area (ECSA), in the glucose oxidation reaction (GOR) and glucose sensors were systematically studied. Kinetic studies using electrochemical quartz crystal microbalance show that the specific activities (S A 1) of the nanocrystals were in the order of t -Oct > Oct > NC, in which the number of moles of glucose per ECSA for PdAu t -Oct was 2.56 × 10-8 mol·cm−2, indicating that glucose was easily bonded to t -Oct with the (2 1 1) facet. By contrast, the results of specific activity (S A 2), estimated by the moles of electrons over ECSA, showed the order of Oct > t -Oct > NC. The S A 2 of PdAu Oct was 6.25 × 10-7 mol·cm−2. The facile electron transfer of GORs occurred via PdAu Oct with an electron-rich Au shell. Additionally, PdAu Oct demonstrated high recoveries when used as a glucose sensor for energy drinks. [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]

[Display omitted] • Various Pt shell structures were synthesised on the surface of Pd NCs. • Pt surface facets impact significantly on the mechanism of neutral GOR. • GOR on the stellated Pd@Pt NCs with (2 1 1) facets occurs via a 12-electron patwahy. • Stellated Pd@Pt NCs are the best catalyst for sequential GOR. • Pd NCs with Pt corners having (2 1 0) and (9 5 0) facets enhance transient catalysis. Nanocrystals with high-indexed facets and low-coordinated atoms exhibit promising electrocatalytic activities. Herein, different Pt shell structures on the surface of Pd nanocubes (Pd@Pt NCs) were synthesised by varying the concentration of Pt precursors. The concave Pd@Pt NCs were used as electrocatalysts for neutral glucose oxidation reactions (GORs); the effect of Pt structure on the catalytic performance was studied. In sequential catalysis, stellated Pd@Pt NCs (Pd@Pt SNC) with (2 1 1) facets had an electron transfer number (N e) of 12.69 and a specific activity of 4.69 × 10−9 mol·g·m−2, markedly higher than that of the other concave Pd@Pt NCs. In transient catalysis, Pd NCs with Pt-coated corners (Pd@Pt CNCC) containing (2 1 0) and (9 5 0) facets demonstrated a sensitivity of 11.06 μA·mM−1·cm−2 and a linear analysis range (2.4–10.6 mM). The high recoveries (98.80%–99.85%) and low relative standards (≤1.06%) in the serum sample corroborate the potential of Pd@Pt CNCC as an enzyme-free glucose sensor. [ABSTRACT FROM AUTHOR]

• Syntheses of CF-NiCo LDHN and with heat treatment at 200 and 400° are demonstrated. • Sequential and transient catalysis of GOR by these NiCo nanomaterials are studied. • CF-NiCo LDHN ([(Ni2+ 0.5 Co3+ 0.5)(OH−) 2 ][Br- 0.5 ·0.5H 2 O]) has remarkable j 0 for GOR. • Glucose dehydrogenation and one-electron release occurred first on the NiCo LDHN. • CF-NiCo LDHN shows high recovery and low RSD (<5%) for sensing glucose. We report a systematic study of carbon fibre (CF)-supported NiCo layered double hydroxide nanosheets (LDHNs) with and without heat treatment at 200 and 400 °C (CF-NiCo LDHN 200 and CF-NiCo oxide nanoparticles (NPs), respectively) as catalysts and sensors for glucose oxidation reactions (GORs). Tafel measurements for the GORs showed that the exchange current density of CF-NiCo LDHN was 1.91 × 10−3 mA·cm−2 at an early rest potential of −0.422 V. This was markedly higher than those of CF-NiCo LDHN 200 (1.22 × 10−3 mA·cm−2 at − 0.352 V) and CF-NiCo oxide NP (1.18 × 10−3 mA·cm−2 at −0.327 V). The electron transfer number and Tafel slopes suggested that the glucose dehydrogenation step and one-electron release occurred first in the GORs. Amperometric measurements revealed high recoveries (101.92% and 98.92%) and low relative standard deviations (1.98% and 2.34%) for the determination of glucose using the CF-NiCo LDHN in sports drink samples and human serum. [ABSTRACT FROM AUTHOR]

[Display omitted] • dGN-supported Pt NPs are prepared and successfully catalyse neutral GOR. • Pt/dGN 600 with point vacancy, 5–8-5, and 5–9 vacancy defect exhibit a remarkable activity. • In-situ GOR kinetics by Pt/dGNs and their activities are studied by EQCM. • Electron transfer numbers for the catalysis of GORs on the various Pt/dGNs were determined. • Pt/dGN 600 showed its potential for being a non-enzymatic glucose sensor. Significantly improving the dispersion of platinum nanoparticles (NPs) over the support is critical to boosting their performance in electrocatalysis. Herein, an effective method is reported to synthesise well-dispersed Pt NPs (∼3 nm) on defective graphene nanosheets (Pt/dGNs) through a self-regulation reduction method of sodium n-dodecyl sulphate (SDS). The dGNs (dGN 600 , dGN 400 , and dGN 200) were rapidly exfoliated and prepared using a sonoelectrochemical method with sonication powers of 600, 400, and 200 W. Consequently, highly dispersed and dense Pt NPs formed on dGN 600 (Pt/dGN 600) with point vacancy, 5–8-5 defect, and 5–9 vacancy defect were obtained. The Pt/dGN 600 exhibited a significant mass activity (5.80 × 1020 molecules· g-1 Pt) for the sequential catalysis of neutral D-glucose oxidation reaction (GOR), where the electron transfer number was 1.13, suggesting that the element step to form gluconolactone. Additionally, amperometric sensor studies for transient catalysis clearly showed the potential of Pt/dGN 600 for use as a non-enzymatic glucose sensor. [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]