Negative Onset Potential Research Articles

Titanium vanadium nitride supported Pt nanoparticles as high-performance catalysts for methanol oxidation reaction

In the present study, Pt nanoparticles (20 wt%) were successfully anchored on vanadium (V)-doped titanium nitride hybrid support, which controllable prepared by adjusting the ratio of precursors. Electrochemical performance of the novel Pt/Ti0.8V0.2N electrocatalyst exhibits well stability and better electrocatalytic activity than the conventional Pt/C electrocatalyst under direct methanol fuel cells (DMFCs) conditions. Notable, Pt/Ti0.8V0.2N exhibits negative onset potential (ca. 0.1 V) and higher current density than Pt/TiN (1.7-fold) and Pt/C (2.5-fold), clearly demonstrating that methanol can be oxidized more easily on Pt/Ti0.8V0.2N catalyst. These results indicate that the V doping has co-catalytic and electronic effects, and the hybrid material is indeed a promising support to improve Pt catalytic activity and durability for practical DMFCs.

Facile synthesis of Pd-Ru-P ternary nanoparticle networks with enhanced electrocatalytic performance for methanol oxidation

Liquid fuel cells have attracted broad research interests for past several decades, especially for direct methanol fuel cells (DMFCs) because of their compact volume, environmentally benign and easy storage. Exploring cost-effective electrocatalysts toward methanol electrooxidation is meaningful for the development of (DMFCs). Herein, a series of PdRu/P network catalysts have been fabricated and modified via a facile and reproducible method taking benzyl alcohol, hydrazine hydrate as solvent and reducing agents, respectively. Profiting from the 3D network structure, the synergistic effect together with the increased electron mobility induced by the addition of nonmetal phosphorous (P). The PdRu/P catalysts display markedly improved efficient electrocatalytic activity with excellent current peak, more negative onset potential, as well as superior long-term stability compared to commercial Pd/C, PdRu and Pd/P prepared under the same condition. In this work, we highlight the effect of the incorporation of nonmetals P on the electrocatalytic performance of PdRu binary catalysts, which will contribute to broadening the application of nonmetal P or even for other nonmetals for electrooxidation. Our efforts will dedicate to accelerating the commercialization of efficient and stable anode catalysts in fuel cells by means of doping transition metals or nonmetals into Pd.

Influence of carbon microstructure on the Li-O2 battery first-discharge kinetics

Defects in the carbon microstructure have been reported to enhance the discharge performance of Li–O2 battery. However, systematic studies correlating the presence of defects with the discharge kinetics have not addressed the variation of carbon electrode surface areas. In this work, carbon blacks and carbon nanofibers with different defect densities were investigated for their discharge properties. The electrolyte-accessible areas of the carbon electrodes were obtained from Cyclic voltammetry measurements. The microstructure and surface areas of the carbons were characterized by Raman spectroscopy, electron microscopy, and N2 isotherm. Linear sweep voltammetry and galvanostatic discharge experiments consistently demonstrated that graphitic carbons have more negative onset potentials and more negative discharge potentials at the same current density than defective carbons. The linear sweep voltammetry data were normalized to the carbon masses, Brunauer–Emmet–Teller surface areas, and double layer capacitance-derived areas for comparison. Plot of inverse charge transfer resistance and double layer capacitance from electrochemical impedance spectroscopy measurements were used to extract current density values without knowledge of electrode areas. The current densities from impedance measurements exhibited good agreement with the data from linear sweep experiments. The electrochemical experiments conclusively showed that defects on the graphitic microstructure increase the discharge kinetics of the Li–O2 battery.

Phosphomolybdate@Carbon‐Based Nanocomposites as Electrocatalysts for Oxygen Reduction Reaction

AbstractFunctional materials as electrocatalysts for the oxygen reduction reaction (ORR) are crucial for several renewable energy applications. Herein, we report the application of several nanocomposites, prepared by the incorporation of a vanadium‐substituted phosphomolybdate [PMo11VO40]4− (PMo11V) into some carbon‐based materials (carbon black (CBV), single‐walled carbon nanotubes (SWCNT) and graphene (GF)), as ORR electrocatalysts. All nanocomposites, denominated as PMo11V@CBV, PMo11V@SWCNT and PMo11V@GF, show electrocatalytic activity for the ORR in acidic medium (pH 2.5 H2SO4/Li2SO4 buffer solution), with a strong dependency between the electrocatalytic ORR performance and the carbon‐based material employed. Among the materials studied, the PMo11V@GF nanocomposite exhibits the most promising performance, having the less negative onset potential (Eonset=‐0.16 V vs. Ag/AgCl (0.18 V vs. RHE)), which is explained by the excellent electronic properties of GF. An ORR process based in a 2‐electron mechanism is assumed for all modified electrodes. The PMo11V‐ and the nanocomposite‐modified electrodes are also effective for the reduction of hydrogen peroxide, with PMo11V@GF displaying the most promising electrocatalytic performance. The successful preparation of the nanocomposites is confirmed by X‐ray photoelectron spectroscopy and Fourier transformed infrared spectroscopy techniques. The electrochemical characterization of all modified electrodes is also reported.

Pt–Ag/C catalyst for methanol oxidation and alcohol tolerant cathode in different electrolytes

Pt–Ag/C catalyst was prepared by sonication to evaluate its catalytic activity for the oxygen reduction (ORR) and methanol oxidation reactions (MOR). The synthesized material was characterized by X-ray diffraction (XRD), elemental disperse spectroscopy (EDS), scanning (SEM) and transmission electron microscopy (TEM) techniques. Cyclic voltammetry, linear voltammetry and chronoamperometry studies were also carried out in acid and alkaline electrolytes with different methanol concentrations (0.0, 0.3 and 0.5 M). Structural properties and elemental composition of bimetallic samples were analyzed by XRD and EDS. According to TEM results, Pt–Ag nanoparticles exhibited a form of spherical agglomerates with poor distribution on carbon. Methanol oxidation reaction (MOR) on Pt–Ag/C in alkaline electrolyte revealed five folds greater activity than in acid medium. Moreover, Pt–Ag/C has exhibited excellent properties as tolerance cathode in acid medium, showing that the activity was not affected with the presence of methanol. However, in alkaline medium the Pt–Ag/C kinetics, as cathode catalyst, was drastically affected by the presence of methanol, presenting a negative onset potential shift, which increased with methanol concentration. The Ag presence and formed Ag-oxide modified the tolerance of methanol for ORR in acid electrolyte and promoted the catalytic activity of Pt for MOR in alkaline electrolyte. Pt/C sample was synthesized and tested at the same conditions for comparison purposes.

Effect of Silver Modification on Glycerol Oxidation Reaction Activity of Palladium Electrode in Alkaline Medium

Introduction Biodiesel fuel (BDF) attracts attention as a carbon-neutral fuel as well as bioethanol. As the production of BDF increases, the production of the glycerol byproduct is also increasing. It is important to develop new uses for glycerol to cope with the mass production of BDF. The use of glycerol as a fuel for direct alcohol fuel cells is promising, because anodic oxidation of glycerol produced by bioprocesses occurs in carbon-neutral cycles and direct glycerol fuel cells are expected to produce electricity with a low environmental load and to be energy efficient. It is well-known that Pd is cheaper than Pt and Au, and Pd-based alloy electrodes are highly active for the oxidation of alcohols in alkaline media. We also have reported the PdAg alloys-loaded carbon exhibited higher glycerol oxidation reaction (GOR) activity and tolerance to poisoning species than Pd.1 The mechanism for GOR, however, is not so clear. In this study we prepared an Ag atomic layer-modified Pd model electrode, and investigated the potential dependence of GOR products by in situ infrared reflectance-absorption spectroscopy (IRAS). In addition, we discussed the GOR mechanism based on these data. Experimental The Ag atomic layer-loaded Pd (Ag/Pd) electrode was prepared by underpotential deposition of Cu (Cu-upd) on a Pt polycrystalline substrate and the following galvanic replacement with Ag. The coverage of Ag (θ Ag) on the Pd substrate was evaluated to be 0.5 from the charges for Cu-upd before and after the Ag modification. 1 M KOH and (1 M KOH + 0.5 M glycerol) solution were used for electrochemical measurements. In situ infrared reflection-absorption spectroscopy (IRAS) was used to qualitatively analyze the products of GOR on the Pd and Ag/Pd electrodes in alkaline solution. All electrochemical measurements were performed at room temperature. Results and Discussion The cyclic voltammograms of the Pd and Ag/Pd electrodes in a (1 M KOH + 0.5 M glycerol) solution is shown in Fig. 1. The Ag/Pd electrode had higher oxidation current and more negative onset potential of the oxidation current than the Pd electrode, clearly indicating that the GOR activity was enhanced by the modification of the Ag atomic layer. In addition, the peak potential of the oxidation current for the Ag/Pd electrode was more positive than that for the Pd electrode, suggesting that the former was superior in tolerance to poisoning species to the latter. IRAS spectra for the Pt electrode exhibited that the absorption peak at 1335 cm-1 assigned to the formation of dihydroxyacetone was mainly increased at lower potentials, but the absorption peak at 1310 cm-1 assigned to the formation of glycerate was increased at higher potentials. This suggests that the secondary OH group in a glycerol molecule is preferentially oxidized at smaller overpotentials, and the primary OH group is greatly oxidized at larger overpotentials. For the Ag/Pd electrode, the oxidation of the primary OH group occurred even at smaller overpotentials, and hydroxypyruvate was also formed at larger overpotentials. Acknowledgement This work was partially supported by JSPS KAKENHI Grant Number 15H04162. Reference 1 B. T. X. Lam, M. Chiku, E. Higuchi, H. Inoue, J. Power Sources, 297, 149 (2015). Figure 1

Nitrogen and sulfur co-doped graphene/carbon nanotube as metal-free electrocatalyst for oxygen evolution reaction: the enhanced performance by sulfur doping

Highly active metal-free electrocatalysts consisting of earth-abundant elements for oxygen evolution reaction (OER) are extremely desired for renewable energy technologies. Here we prepare the nitrogen and sulfur co-doped graphene/carbon nanotube (NS-GR/CNT) with 3D architecture by one-step hydrothermal method, which presents good performance for OER. The as-prepared NS-GR/CNT exhibits more negative onset potential and lower Tafel slope (0.56V, 103mVdecade−1 vs. S.C.E. in 0.1M KOH) compared to single N doped graphene/carbon nanotube (0.65V, 285mVdecade−1), which indicates S doping can significantly enhance the OER performance. The X-ray photoelectron spectroscopy reveals that the thiophene-like S (C-S-C) is the dominant S species in all the S doped samples. NS-GR/CNT with C-S-C content of 0.26% has the Tafel slope of 151mVdecade−1 while the value for NS-GR/CNT with C-S-C content of 1.09% is 103mVdecade−1. The decreased Tafel slope demonstrates the catalytic kinetics are highly correlated with the content of C-S-C. Density functional theory calculations suggest that C-S-C may improve the catalytic kinetics by facilitating the adsorption of the OH− intermediate. Besides, the 3D architecture composed of graphene and CNTs also contributes to the good performance and chronoamperometric measurement demonstrates the good durability of NS-GR/CNTs.

Ni-doped CoFe2O4 Hollow Nanospheres as Efficient Bi-functional Catalysts

Ni-doped spinel oxides NixCo1-xFe2O4 (x=0, 0.25, 0.5, 0.75) hollow nanospheres electrocatalysts are synthesized with a simple hydrothermal approach. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) results reveal that the morphology, hollow and spinel structures of the cobalt ferrites remain unchanged with doping. The electrocatalytic activity of the Ni-doped CoFe2O4 with different doping contents has been studied and compared with the pure CoFe2O4 hollow nanospheres in alkaline solution by using rotating ring-disk electrode (RRDE) technique. For ORR, the Ni0.5Co0.5Fe2O4 (x=0.5) exhibits as the most active catalyst with the highest diffusion limited current density and more positive onset potential. Whereas, the Ni0.75Co0.25Fe2O4 (x=0.75) shows the best catalytic activity for OER with more negative onset potential (0.27V vs. Ag/AgCl) and maximum current density (36.0mA/cm2 at 1.0V). X-ray photoelectron spectra (XPS) measurements reveal that the oxygen vacancy on the oxide surfaces increases, while the cations occupied ratio on octahedral/tetrahedral sites in spinel structures decreases along with the increasing of the Ni doping content. Combining with the charge transfer resistance measured by electrochemical impedance spectroscopy (EIS), these three factors work synergistically on the catalytic activities of the Ni-doped CoFe2O4 hollow nanospheres.

Free-Standing 3D Hierarchical Carbon Foam-Supported PtCo Nanowires with “Pt Skin” as Advanced Electrocatalysts

A two-step method was used for fabricating PtCo alloy nanowires supported on free-standing carbon foam network (PtCo-NWs/CF). First, Co nanowires (Co-NWs) were successfully in situ formed on CF (Co-NWs/CF) through a hydrothermal procedure with a subsequent post annealing treatment. Second, PtCo-NWs/CF composite was prepared via the displacement reaction between PtCl42- and the as-synthesized Co-NWs in the presence of ascorbic acid. Moreover, by a simple electrochemical process, a “Pt-skin” can be formed on the PtCo nanowires. Due to the 3D hierarchical micron-grade porous carbon support and the PtCo alloy nanowires with a synergy effect between Pt and Co, the PtCo-NWs/CF shows excellent electrocatalytic activity toward ethanol oxidation reaction (EOR) and oxygen reduction reaction (ORR, undergoes a 4e− pathway). The prepared PtCo-NWs/CF displayed a more negative onset potential and higher current density for the ethanol oxidation compared to commercial Pt/C and the Pt/CF. For ORR, at −0.6V, the PtCo-NW/CF shows a mass activity of 2.03AmgPt−1, which is almost 6.34 and 3.44 times higher than those of the commercial Pt/C (0.32AmgPt−1) and Pt/CF (0.59AmgPt−1). Such high electrocatalytic performances of the PtCo-NWs/CF for both ethanol oxidation and oxygen reduction render it a promising catalyst for fuel cells.

A ternary nanocatalyst of Ni/Cr/Co oxides with high activity and stability for alkaline glucose electrooxidation

A novel ternary nanocatalyst of Ni-Cr-Co oxides is synthesized as anode electro-catalysts for glucose oxidation. The nanostructure is characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM), which indicates that the catalyst particles are well dispersed with average size of 30nm when the calcination temperature is 500°C. The electrochemical performance is evaluated via cyclic voltammetry (CV). Compared with the bimetallic Ni-Cr and Ni-Co nanocatalysts, Ni-Cr-Co electrocatalysts exhibites more negative onset potential (0.4V) and high oxidation peak current density (23.8mAcm−2) in alkaline media towards glucose oxidation. Meanwhile, the results also show that the Ni-Cr-Co nanomaterial possesses good performance of anti-poisoning capability, reproducibility and long-time stability, which make it an excellent candidate for fuel cell electrocatalyst.

Mg-Zr Cosubstituted Ta3N5 Photoanode for Lower-Onset-Potential Solar-Driven Photoelectrochemical Water Splitting.

In p/n photoelectrochemical (PEC) cell systems, a low onset potential for the photoanode, as well as a high photocurrent, are critical for efficient water splitting. Here, we report a Mg-Zr cosubstituted Ta3N5 (Ta3N5:Mg+Zr) photoanode, designed to provide a more negative onset potential for PEC water splitting. The anodic photocurrent onset on Ta3N5:Mg+Zr was 0.55 V(RHE) under AM 1.5G-simulated sunlight, which represented a negative shift from the ca. 0.8 V(RHE) for pure Ta3N5. This negative shift in the onset potential of PEC water splitting was attributed to the change in the bandgap potential due to partial substitution by the foreign ions Mg(2+) and/or Zr(4+).

Nano-engineered ZnO/CeO2 dots@CNFs for fuel cell application

Well-dispersed ZnO(x)CeO2(1−x) nanodots@carbon nanofibers as anode catalysts for the electrooxidation of methanol were synthesized by an easy-controlled template-free method. Their structure and morphology were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), field-emission scanning electron microscopy (FESEM) equipped with rapid EDX (energy dispersive analysis of X-ray). The appealed characterization techniques specified that the obtained material is carbon nanofibers decorated by ZnO and CeO2 nanodots. The electrochemical oxidation of methanol on ZnO(x)CeO2(1−x) nanodots@CNFs modified glassy carbon electrode in alkaline solutions was systematically evaluated by cyclic voltammetry (CV) method. A detailed investigation is made for the electrocatalytic oxidation of methanol by varying methanol concentration. The corresponding current densities of ZnO(60%)CeO2(40%) nanodots@CNFs and ZnO(40%)CeO2(60%) nanodots@CNFs were 5.3 and 16.3mA/cm2, respectively. Moreover, negative onset potential (−50mV vs. Ag/AgCl) was observed when ZnO(40%)CeO2(60%) nanodots@CNFs were utilized, which is a superior value among the reported non-precious electrocatalysts. These results suggested cheap and effective nanomaterials as non-precious catalyst for DMFCs application and pave the way to further improve the performance in energy and environmental applications.

Ba0.95La0.05FeO3−δ–multi-layer graphene as a low-cost and synergistic catalyst for oxygen evolution reaction

Oxygen evolution reaction (OER) is critical to many important energy conversion and storage processes. However, the kinetics of OER is typically sluggish, and conventional OER catalysts are scarce and expensive. Hence, inexpensive and effective catalysts that accelerate the OER kinetics and reduce the overpotential are urgently needed. In this paper, we reported multi-layer graphene-supported perovskite Ba0.95La0.05FeO3−δ (BLF–MLG) as a highly active OER catalyst. Electrochemical results showed that the BLF–MLG hybrid exhibited a high current density (∼23mA/cm2 at 0.60V vs. mercury/mercury oxide electrode (MMO)) and a more negative onset potential (∼0.43V vs. MMO). Furthermore, the hybrid showed a smaller Tafel slope (77mV/decade) and improved long-term stability. The remarkable OER performance is mainly attributed to the synergistic effect between BLF and graphene.

Tungsten Carbide Synthesized by Polystyrene Sphere Template Method Promoting Pd Electrocatalyst for Alcohol Oxidation in Alkaline Media

Tungsten carbide (WC) particles loading on hollow carbon spheres (HCS) have been synthesized by using ammonium metatungstate as W source, glucose as carbon source, P123 as dispersant and polystyrene sphere as template. The typical WC-HCS composite has the WC particle sizes of 5–20 nm, specific surface area of 445 m2 g−1, pore volume of 0.24 cm3 g−1 and hollow spherical structure. The above structures of WC-HCS favor dispersion of Pd particles and mass transfer. Therefore, the Pd/WC-HCS electrocatalyst has 4.6 times higher peak current density and 130 mV more negative onset potential than that of Pd/C for ethanol oxidation in alkaline solution. The mass transfer property of WC-HCS (due to structure effect) and promotion effect of WC on Pd are believed to be the origins of the excellent performances.

High-Efficiency Palladium Nanoparticles Supported on Hydroxypropyl-β-Cyclodextrin Modified Fullerene [60] for Ethanol Oxidation

In this paper, Palladium nanoparticles with uniform size and high dispersion have been successfully assembled on hydroxypropyl-β-Cyclodextrin (HP-β-CD) modified C60 (abbreviated as HP-β-CD-C60) via a sodium borohydride reduction process. According to the transmission electron microscopy (TEM) measurements, the average particle size of the as-prepared Pd nanoparticles dispersed on HP-β-CD modified C60 is 2.7nm. Electrochemical studies reveal that the Pd/HP-β-CD-C60 modified electrode shows a significantly high electrocatalytic activity, much more negative onset potentials and better stability than electrodes modified by other electrocatalysts for ethanol oxidation, which indicates that it is a better potential candidate for application in a direct ethanol fuel cell (DEFC).

Pd nanoparticles supported on phenanthroline modified carbon as high active electrocatalyst for ethylene glycol oxidation

Modified carbon is fabricated by applying phenanthroline as nitrogen source and used as support (PMC) to immobilize Pd nanoparticles. Because the nitrogen-doping not only changes physicochemical and electronic properties of carbon but also serves as basic or coordination sites to stabilize and produce additional electronic activation for Pd, the Pd/PMC exhibits excellent electrochemcial performance for ethylene glycol oxidation. Compared to conventional Pd/C catalyst, the Pd/PMC catalyst has a larger electrochemically active surface area, 50mV more negative onset potential, 1.77 times oxidation current and superior stability.

Co/CeO2-decorated carbon nanofibers as effective non-precious electro-catalyst for fuel cells application in alkaline medium

In this study, Co/CeO2 decorated carbon nanofibers are introduced as effective electro-catalyst for methanol oxidation. Poly(vinyl alcohol) was used as carbon source due to its high carbon content characteristic as compared to many others polymer precursors for CNFs synthesis. Preparation of the introduced nanofibers could be achieved by calcination of electrospun nanofibers composed of cerium (III) acetate hydrate, cobalt (II) acetate tetra hydrate and poly(vinyl alcohol) in nitrogen environment at 700°C. The produced sintered powder was characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), field-emission scanning electron microscopy (FESEM) equipped with rapid EDX (energy dispersive analysis of X-ray). The invoked characterization techniques indicated that the obtained material is carbon nanofibers decorated by Co/CeO2 nanoparticles. Investigation of the electrocatalytic activity of the introduced decorated nanofibers toward methanol oxidation indicated good performance as the corresponding current density increased with increasing methanol content in the alkaline medium. Interestingly, the introduced catalyst revealed negative onset potential (−50mV vs. Ag/AgCl) which is a superior value among the reported non-precious electrocatalyst. Moreover, methanol oxidation takes place at relatively low applied voltage (180mV vs. Ag/AgCl) which adds additional advantage for the introduced material. Overall, the introduced study opens new avenue for cheap and effective transition and rare earth family-based nanomaterials as non-precious catalyst for fuel cell application.

A cobalt phosphide on carbon decorated Pt catalyst with excellent electrocatalytic performance for direct methanol oxidation

An ion-exchange method has been developed to synthesize Co2P on graphitized carbon and further deposit Pt nanoparticles for the first time. Various methods have been used to characterize the property of the Pt deposited on Co2P/C (Pt–Co2P/C). It shows an improved catalytic activity and stability for methanol electrooxidation. The electrochemical testing proves that the Pt–Co2P/C catalyst has nearly four times the catalytic activity and 120 mV more negative onset potential compared with commercial Pt/C. The reason of the highly enhanced electrocatalytic activity and poisoning resistance of the Pt–Co2P/C catalyst is discussed.

Highly Efficient Membraneless Glucose Bioanode Based on Corynascus thermophilus Cellobiose Dehydrogenase on Aryl Diazonium‐Activated Single‐Walled Carbon Nanotubes

AbstractWe present an approach for electrode modification by using the oxidoreductase cellobiose dehydrogenase from the ascomycete Corynascus thermophilus (CtCDH). CtCDH is a two‐domain enzyme, in which the catalytic dehydrogenase domain (DHCDH) hosts flavin adenine dinucleotide (FAD) as cofactor and is connected through a flexible linker to a small cytochrome domain with a heme b cofactor (CYTCDH). This domain is responsible for the electron transfer from DHCDH to macromolecular electron acceptors, and is capable of direct electron transfer (DET) with electrode surfaces. CtCDH is optimal at pH values between 7 and 9 and exhibits one of the lowest apparent KM values for glucose (2.4×104 μM) in contrast to the majority of other CDHs, which have acidic optimal pH values and have very low or no activity for glucose. Glassy carbon (GC) electrodes were modified by drop‐casting single‐walled carbon nanotubes (SWCTs) and further modifying with aryl diazonium salts (DS). When adsorbed on such GC‐SWCT‐DS electrodes, CYTCDH showed efficient DET in the presence of a substrate. Six different functional groups for the aryl amines were studied and compared to non‐DS modified GC‐SWCT electrodes. The charge of the grafted aryl amines was investigated and it was found that surfaces modified with aniline, 4‐aminophenol, and 4‐aminobenzoic acid (ABA) contain negative charges at pH 7.4. On the other hand, surfaces modified with p‐phenylenediamine (PD), N,N‐dimethyl‐p‐phenylenediamine, and N,N‐diethyl‐p‐phenylenediamine remain uncharged. To date, the highest DET current density (JMAX=32.5 μA cm−2 for lactose and JMAX=16.2 μA cm−2 for glucose) for a CDH‐modified electrode at human physiological pH can be obtained by using a GC‐SWCT‐ABA CtCDH modified electrode. The use of glutaraldehyde (GA) in GC‐SWCT‐PD‐modified electrodes increases the JMAX twofold. The modified electrodes with DS showed a more negative onset potential for the catalytic current. For GC‐SWCT‐ABA modified electrodes and GC‐SWCT‐PD with GA, a change in the onset potential of −62 and −66 mV, respectively, was found compared with non‐DS modified electrodes. The prepared bioanodes show a loss in response current of 15 % after 9 days of continuous measurements from the original signal in 5 mM glucose, using 50 mM phosphate buffer solution at pH 7.40 at 37 °C.

Active and Stable Platinum/Ionic Liquid/Carbon Nanotube Electrocatalysts for Oxidation of Methanol

Platinum (Pt) nanoparticles (NPs) on carbon nanotubes (CNTs) from PtCl62– ions through a facile ionic liquid (IL)-assisted method has been developed and used for methanol oxidation. 1-Butyl-3-methylimidazolium (BMIM) with four different counter ions (PF6–, Cl–, Br–, and I–) have been tested for the preparation of Pt/IL/CNT nanohybrids, showing the counter ions of ILs play an important role in the formation of small sizes of Pt NPs. Only [BMIM][PF6] and [BMIM][Cl] allow reproducible preparation of Pt/IL/CNT nanohybrids. The electroactive surface areas of Pt/[BMIM][PF6]/CNT, Pt/[BMIM][Cl]/CNT, Pt/CNT, and commercial Pt/C electrodes are 62.8, 101.5, 78.3, and 87.4 m2 g-1, respectively. The Pt/[BMIM][Cl]/CNT nanohybrid-modified electrodes provide higher catalytic activity (251.0 A g–1) at a negative onset potential of -0.60 V than commercial Pt/C-modified ones do (133.5 A g–1) at -0.46 V. The Pt/[BMIM][Cl]/CNT electrode provides the highest ratio (4.52) of forward/reverse oxidation current peak, revealing a little accumulation of carbonaceous residues.