Catalytic Activity For Electrochemical Reduction Research Articles

Biocathodes reducing oxygen in BPE-ECL system for rapid screening of E. coli O157:H7

After discovery of electron transfer from bacteria, most bacteria known to be electrochemically active are utilized as a self-regenerable catalyst at the anode of microbial fuel cells (MFCs). However, the reverse phenomenon, cathodic catalysts is not so widely researched. This present study demonstrated that E. coli O157:H7 was electrochemically active, and it was able to catalyze oxygen reduction at the cathode of bipolar electrode (BPE). Applying a constant potential to the BPE, E. coli O157:H7 can catalyze electrochemical reduction of O2, decrease the overpotential of O2 reduction at the cathode, which in turn generates an electrochemiluminescence (ECL) reporting intensity change at the anode. Significantly, a majority of food matrix does not exhibit catalytic activity for electrochemical reduction of O2. Meanwhile, due to the physically separation of two poles of closed BPE, complex food matrix at the cathode does not interfere with the ECL reaction at the anode. Therefore, the effect of food matrix is negligible when measuring E. coli O157:H7 levels in food. A low detection limit of 10 CFU mL−1 E. coli O157:H7 could be identified within 1 h. Thus, biocathodes reducing oxygen in BPE-ECL system has shown excellent characteristics in the field of rapid detection of electroactive bacteria in food.

Design of CuInS2 hollow nanostructures toward CO2 electroreduction

The sharp rise of CO2 in the atmosphere has become a potential threat to global climate, which results from the massive utilization of fossil fuel since the industry revolution. CO2 electroreduction provides us a new possibility of utilizing CO2 as a carbon feedstock for fuel and commercial chemicals generation. In this article, a new method is developed for synthesizing CuInS2 hollow nanostructures through the Kirkendall effect. The CuInS2 hollow nanostructures exhibit excellent catalytic activity for electrochemical reduction of CO2 with particular high selectivity, achieving high faradaic efficiency for HCOOH of 72.8% at −0.7 V. To elucidate the mechanisms, operando electrochemical Raman spectroscopy is employed to examine the CO2 reduction process. This work provides new insights into the design of hollow nanostructures toward electrocatalytic CO2 conversion and offers us an effective and reliable way for real-time investigation of electrochemical CO2 reduction reaction processes.

Ligand-free gold nanoparticles supported on mesoporous carbon as electrocatalysts for CO2 reduction

Gold nanoparticles (AuNPs) have shown good catalytic activity for electrochemical CO2 reduction. However, they are typically stabilized by poorly conductive organic ligands which partially block their activity for electrocatalysis. In this work, we report a one-pot organic ligand-free synthesis of AuNPs on mesoporous carbon (MC). The size of the AuNPs is controlled by the micro- and mesoporosity of the carbon support and the mass ratio employed of the gold precursor/MC. The produced AuNPs-MC hybrid material, with the largest amount of small AuNPs (1–3 nm), shows good catalytic activity for the electrochemical reduction of CO2 to CO in aqueous electrolyte. The optimized selectivity is recorded to be, on average, 80% with a mass activity of 12.8 A g–1 at an overpotential of 550 mV. The catalyst stability of the material is investigated to give insight into the irreversible deactivation mechanism occurring at the surface of AuNPs. Using 6-mercapto-1-hexanol as the ligand on AuNPs shows a dual effect in terms of an improved stability but a lowered activity.

Identification of intrinsic catalytic activity for electrochemical reduction of water molecules to generate hydrogen.

Insufficient hydronium ion activities at near-neutral pH and under unbuffered conditions induce diffusion-limited currents for hydrogen evolution, followed by a reaction with water molecules to generate hydrogen at elevated potentials. The observed constant current behaviors at near neutral pH reflect the intrinsic electrocatalytic reactivity of the metal electrodes for water reduction.

Coaxial electrospinning route to prepare Au-loading SnO2 hollow microtubes for non-enzymatic detection of H2O2

Au-loading SnO2 hollow microtubes (Au-SnO2-MTs) have been successfully prepared by the coaxial electrospinning method, where the sol solution containing poly-vinylpyrrolidone and metal salts were used as outer solution and paraffin was used as inner solution, respectively. The combined characterizations of scanning electron microscopy and X-ray diffraction indicating the successful preparation of Au-SnO2-MTs with the diameter of MTs about 500-600nm, and the thickness of the hollow MTs about 70-80nm. It is also found that the Au-SnO2-MTs exhibit catalytic activity for electrochemical reduction of H2O2, leading to a non-enzymatic H2O2 sensor. The H2O2 sensor thus obtained shows the linear detection range from 10μM to 1mM (r=0.997), and the detection limit about 0.60μM at a signal-to-noise ratio of 3. Furthermore, the H2O2 sensor also exhibits excellent selectivity for H2O2 in comparison to other normally co-existing electroactive species (such as dopamine, ascorbic acid, uric acid and glucose) and inorganic anions.

NAD + hydrogenation on Au electrode deposited on modified glassy carbon

Gold nanoparticles(AuNP) were electrodeposited on a glassy carbon(GC) which was electrochemically modified by potentiodynamic cyclic polarization in acidic medium. The AuNP deposits were characterized by scanning electron microscopy, cyclic voltammetry, chronoamperometry and linear sweep voltammetry. Results of these studies showed that very small sized AuNP are deposited with significantly high particle density which is attributed to the surface modification of GC. The resulted AuNP/GC electrode showed high catalytic activity for electrochemical reduction of NAD + to NADH, indicating its potential for electrocatalytic applications.

Direct electrochemistry of hemoglobin in cetylpyridinium bromide film: Redox thermodynamics and electrocatalysis to nitric oxide

Hemoglobin was successfully immobilized in cetylpyridinium bromide (CPB) film on a polyacrylamide (PAM) modified glassy carbon electrode (GC). Cyclic voltammetry showed a pair of well-defined and nearly reversible CV peaks at about −0.2165 V vs SCE (pH = 4.22), indicating the character of Hb heme Fe(II)/heme Fe(III) redox couple. The apparent standard potentials of hemoglobin in the CPB were linearly varied with pH in the range from 4.22 to 9.18 with a slope of −48.85 mV pH −1, implying that one proton was accompanied with one electron transferred in the electrochemical reaction. The adsorption of Hb on the surface of PAM/GC electrode have been investigated by electrochemical impedance spectroscopy. The apparent standard potentials of hemoglobin were also studied through direct electrochemistry method as a function of temperature and the thermodynamic parameters (Δ S rc and Δ H rc) for the protein redox were calculated. Hemoglobin in the CPB exhibited catalytic activity for electrochemical reduction of NO.

Electroreduction of Oxygen by Myoglobin on Multi-walled Carbon Nanotube-Modified Glassy Carbon Electrode

Abstract Direct electrochemical response of myoglobin (Myb) on multi-walled carbon nanotube (MWNT)-modified glassy carbon (GC) electrode was observed. Interestingly, Myb on the MWNT exhibited an elegant catalytic activity for electrochemical reduction of oxygen (O2), based on which an unmediated biosensor for O2 was developed.

Electrochemically Controlled Preparation of Platinum-Poly(amidoamine) Dendrimer Hybrid Nanowires and Their Characterization

Platinum-dendrimer hybrid nanowires were prepared by electrochemical reduction of the poly(amidoamine) (PAMAM) dendrimer-platinum(IV) complexes on carbon electrodes covered with alumina template membranes and characterized using scanning probe microscopy and transmission electron microscopy. Direct electrochemical deposition of the fourth and fifth generation dendrimer coordinated platinum ion complexes resulted in formation of well-defined nanowires. The electrochemical reduction of platinum(IV) complexes with fourth or fifth generation PAMAM dendrimers led to the formation of nanowires, due perhaps to the cross-linking of dendrimer molecules via complex formation of amine groups with platinum(IV), intermolecular interaction between dendrimer branches, and potential induced force between the electrode surface and platinum(IV)-dendrimer complexes. The nanosized platinum-dendrimer hybrid nanowires prepared electrochemically on glassy carbon electrodes displayed good catalytic activity for electrochemical reduction of oxygen and oxidation of alcohols. © 2003 The Electrochemical Society. All rights reserved.

Direct electrochemistry of hemoglobin in egg–phosphatidylcholine films and its catalysis to H 2O 2

Direct electrochemistry of hemoglobin was observed in stable thin film composed of a natural lipid (egg–phosphatidylcholine) and hemoglobin on pyrolytic graphite (PG) electrode. Hemoglobin in lipid films shows thin layer electrochemistry behavior. The formal potential E°′ of hemoglobin in the lipid film was linearly varied with pH in the range from 3.5 to 7.0 with a slope of −46.4 mV pH −1. Hemoglobin in the lipid film exhibited elegant catalytic activity for electrochemical reduction of H 2O 2, based which a unmediated biosensor for H 2O 2 was developed.

Catalytic activity for electrochemical reduction of oxygen of lanthanum nickel oxide and related oxides

Catalytic activity for electrochemical reduction of oxygen of lanthanum nickel oxide and related oxides

Catalytic activity for electrochemical reduction of oxygen of lanthanum nickel oxide and related oxides

The catalytic activity for oxygen reduction of lanthanum nickel oxide was affected by the kind and amount of the substituted transition metal M to give LaNi 1− x M x O 3, where M is either one of Fe, Co or V. It was found that the catalytic activity was definitely influenced by the overlap integral between the e g orbital of the transition metal and the sp σ orbital of oxygen, and that the larger the overlap integral is, the higher the electrocatalytic activity. The plausible rate determining step in a low polarization region is MO 2H+ e→MO 2H −, and in a high polarization region the step of oxygen adsorption. Importance of the overlap integral to electrocatalysis is discussed by applying the theory of σ * band formation of the oxide to interaction between the e g orbital of the transition metal of the oxide and the molecular orbital of an oxygen molecule adsorbed on the electrode surface.