Synergistic Electrocatalytic Effect Research Articles

Carbothermal Shock Synthesis of Multimetallic, Solid Solution Electrocatalysts for Air-Based Batteries

Multicomponent nanomaterials are extremely difficult to synthesize by conventional methods. Accordingly, nanoparticles composed of immiscible elemental combinations tend to phase-separate rather than form singe-phase solid solutions, which limits the compositional space. A synthetic technique that facilitates kinetic control over thermodynamic mixing regimes is therefore advantageous and offers untold scientific and technological opportunities. Here, we present a general route to alloy up to eight dissimilar elements into high entropy alloy nanoparticles (HEA-NPs) through a facile and tunable synthesis method: carbothermal shock (CTS).1 CTS employs flash heating and cooling of metal precursors on carbon to produce multimetallic nanoparticles with tailored elemental compositions, particle sizes, and structural complexity. Uniform mixing of nearly any metallic combination is achieved through high temperature exposure (~2000 K) during the thermal shock (55 ms) process, while rapid quenching (~105 K/s) retains this high-entropy state to form single-phase solid solutions. This new synthetic technique promotes materials discovery and design for a wide range of applications, including catalysis and energy storage. Inspired by the performance of quinary HEA-NPs as ammonia oxidation catalysts, novel solid solution nanoparticles (with 2 or more metallic elements) are synthesized and evaluated as electrocatalysts in air-based batteries, such as lithium-oxygen (Li-O2) and Li-CO2. In this way, HEA-NPs composed of catalytically active elements may impart synergistic electrocatalytic effects to improve overall battery performance. This talk will describe the process and underlying mechanism to synthesize HEA-NPs, the overall capabilities of the CTS method, and recent results on electrocatalyst development towards Li-air battery applications.

One‐step Synthesis of AuAg Alloy Nanodots and its Electrochemical Studies towards Nitrobenzene Reduction and Sensing

AbstractEfficient, stable, and low‐cost electrocatalysts for the degradation and sensing of environment pollutants are essential components of clean environment monitoring. Here we report, one‐step synthesis and characterization of 1–3 nm diameter sized bi‐metallic AuAg nanodots (NDs) embedded in amine functionalized silicate sol‐gel matrix (SSG) and its electrochemical studies toward nitrobenzene. The SSG was used as a reducing agent as well as stabilizer for the prepared mono‐ and bi‐metallic nanoparticles (NPs). From the HRTEM, STEM‐EDS and XPS analyses, the bi‐metallic AuAg NDs were identified as an alloy and not the mixtures of Au and Ag NPs. Characteristic surface plasmon resonance (SPR) band between the Au and Ag NPs SPR absorption region was noticed for the prepared AuAg NDs. The AuAg alloy NDs with different concentrations of Au and Ag (Au25Ag75, Au50Ag50 and Au75Ag25 NDs) modified electrodes exhibited synergistic electrocatalytic effect than did the Au and Ag NPs towards nitrobenzene reduction and detection. Together with ultra‐small size and exceptional colloidal stability features within these SSG‐AuAg NDs pave convenient way for nanotechnology‐based catalysts development and sensor applications.

Topotactic transition of α-Co(OH)2 to β-Co(OH)2 anchored on CoO nanoparticles during electrochemical water oxidation: synergistic electrocatalytic effects.

Herein, we report a single step, anionic surfactant-assisted, low temperature-hydrothermal synthetic strategy of CoO nanoparticles anchored on β-Co(OH)2 nanosheets which show a low overpotential (295 mV @ 10 mA cm-2) for the oxygen evolution reaction (OER). They also demonstrate much better kinetic parameters compared to the state-of-the-art RuO2. Interestingly, under the OER operational conditions (in alkaline medium), the topotactic transformation of α-Co(OH)2 to a stable Brucite-like β-Co(OH)2 phase leads to a synergistic interaction between the β-Co(OH)2 sheets on the CoO nanoparticles for enhancing the OER electrocatalytic activity.

Experimental and theoretical insights into sustained water splitting with an electrodeposited nanoporous nickel hydroxide@nickel film as an electrocatalyst

Electrodeposited nanoporous Ni(OH)2@Ni film acts as a Janus electrocatalyst for the hydrogen evolution and oxygen evolution reaction, and overall water splitting, exhibiting superior activities and exceptional long-term stability. Theoretical calculations show that the synergistic electrocatalytic effects of Ni(OH)2 and Ni are responsible for the high activities.

A novel electrochemical biomimetic sensor based on poly(Cu-AMT) with reduced graphene oxide for ultrasensitive detection of dopamine

A polymerized film of copper-2-amino-5-mercapto-1,3,4-thiadiazole (Cu(II)-AMT) complex (poly(Cu-AMT)) was successfully achieved via a simple and low-cost electrochemical methodology. Subsequently, a noncovalent nanohybrid of poly(Cu-AMT) with reduced graphene oxide (rGO) (rGO-poly(Cu-AMT)) was prepared through π–π stacking interaction as an efficient mimetic enzyme for the ultrasensitive and selective detection of dopamine (DA). The rGO-poly(Cu-AMT) nanocomposites showed considerable mimetic enzyme catalytic activity, which may be attributed to the significant promotion of the electron transfer between the substrate and graphene-based carbon materials, and also the synergistic electrocatalytic effect in mimetic enzyme between rGO sheet and poly(Cu-AMT). The electrocatalytic and sensing performances of the biomimetic sensor based on the rGO-poly(Cu-AMT) nanocomposites were evaluated in detail. The biomimetic sensor enables a reliable and sensitive determination of DA with a linear range of 0.01–40μM and a detection limit of 3.48nM at a signal-to-noise ratio of 3. In addition, we applied the proposed method to detect DA in real sample with satisfactory results. Accordingly, the rGO-poly(Cu-AMT) is one of the promising mimetic enzyme for electrocatalysis and biosensing.

Incorporation of gold nanoparticles into Langmuir-Blodgett films of polyaniline and montmorillonite for enhanced detection of metallic ions

We report on effects from incorporating gold nanoparticles (AuNPs) into Langmuir-Blodgett (LB) films of emeraldine salt polyaniline (PAni-ES) and organophilic montmorillonite clay (OMt). The synergistic electrocatalytic effect induced by AuNPs led to an enhanced performance in detecting trace levels of cadmium (Cd2+), lead (Pb2+) and copper (Cu2+) ions. Detection was carried out using square wave anodic stripping (SWAS) voltammetry using ITO electrodes modified with LB films made with three supramolecular architectures: PAni-ES/AuNPs, OMt/AuNPs and OMt/AuNPs/PAni-ES, and compared to LB films without AuNPs. The incorporation of AuNPs induced secondary doping of PAni-ES, inferred from FTIR, Raman and UV–vis. absorption spectroscopies. The PAni-ES chains probably became more extended and could intercalate into the OMt galleries, causing an increased interlayer spacing according to X-ray diffraction data. These results demonstrate the possible control of film properties by exploiting molecular-level interactions in multicomponent nanostructured films.

Three-Dimensional Structures of MoS2@Ni Core/Shell Nanosheets Array toward Synergetic Electrocatalytic Water Splitting.

Hydrogen evolution reaction (HER) in alkaline media using non-noble metal catalysts with great efficiency represents a critical challenge in current water-alkaline and chlor-alkali electrolyzers. Herein, we demonstrate that the MoS2@Ni core/shell nanosheets array vertically aligned on carbon cloth (MoS2@Ni/CC) is a highly active electrocatalyst for HER. In alkaline solutions, MoS2@Ni/CC needs overpotentials of 91, 118, and 196 mV to approach current densities of 10, 20, and 100 mA cm(-2), respectively, exceeding behavior of commercial Pt/C catalyst at high current densities. Additionally, this catalyst also exhibits excellent electrocatalytic activity toward HER in neutral electrolytes. Such high hydrogen evolution activities are due to synergistic electrocatalytic effects between MoS2 core and Ni shell.

Electrochemical Biosensor Utilizing Supramolecular Association of Enzyme on Sol−gel Matrix Embedded Gold Nanoparticles Supported Reduced Graphene Oxide−cyclodextrin Nanocomposite

AbstractHerein we present β‐cyclodextrin (CD)‐functionalized reduced graphene oxide (RGO) nanosheets supported on silicate sol‐gel matrix‐embedded gold nanoparticles (Au NPs) modified electrode as a new affinity binding nanocomposite. The modified electrode is fabricated through layer‐by‐layer drop casting followed by immobilization of chemically modified enzyme conjugate (horse radish peroxidase (HRP)−adamantane carboxylic acid (ADA)). This affinity system is based on the supramolecular association between CDs and HRP−ADA and is mimicking the biological avidin−biotin interactions. CDs‐functionalized RGO (RGO−CD) functions as a macrocyclic host to form stable supramolecular inclusion complexes with enzyme conjugate. Besides Au NPs improve the interfacial interaction with RGO−CD nanosheets, and thus exhibit synergistic electrocatalytic effect toward H2O2 reduction in the presence of 1 mM hydroquinone.

Multisource Synergistic Electrocatalytic Oxidation Effect of Strongly Coupled PdM (M = Sn, Pb)/N-doped Graphene Nanocomposite on Small Organic Molecules.

A series of palladium-based catalysts of metal alloying (Sn, Pb) and/or (N-doped) graphene support with regular enhanced electrocatalytic activity were investigated. The peak current density (118.05 mA cm−2) of PdSn/NG is higher than the sum current density (45.63 + 47.59 mA cm−2) of Pd/NG and PdSn/G. It reveals a synergistic electrocatalytic oxidation effect in PdSn/N-doped graphene Nanocomposite. Extend experiments show this multisource synergetic catalytic effect of metal alloying and N-doped graphene support in one catalyst on small organic molecule (methanol, ethanol and Ethylene glycol) oxidation is universal in PdM(M = Sn, Pb)/NG catalysts. Further, The high dispersion of small nanoparticles, the altered electron structure and Pd(0)/Pd(II) ratio of Pd in catalysts induced by strong coupled the metal alloying and N-doped graphene are responsible for the multisource synergistic catalytic effect in PdM(M = Sn, Pb) /NG catalysts. Finally, the catalytic durability and stability are also greatly improved.

A novel sensor based on electrodeposited Au–Pt bimetallic nano-clusters decorated on graphene oxide (GO)–electrochemically reduced GO for sensitive detection of dopamine and uric acid

Sensitive and simultaneous detection of dopamine (DA) and uric acid (UA) by a sensor based on in-situ electrodeposited Au–Pt bimetallic nano-clusters decorated on graphene oxide (GO)–electrochemically reduced GO (ERGO) modified glassy carbon electrode (GCE) was presented. The synergistic electrocatalytic effect of Au–Pt bimetallic nano-clusters and GO–REGO was investigated. First, the comparisons of electrochemical properties for GO, GO–REGO, Au (or Pt) nanoparticles, Au–Pt bimetallic nano-clusters decorated on GO–REGO were studied in detail. Second, electrochemical parameters of DA and UA were evaluated. It was observed that for the novel Au–Pt/GO–ERGO nanocomposites, GO–ERGO could provide much wider separation of the oxidation peak potentials of DA and UA, while Au–Pt bimetallic nano-clusters could speed up the electron transfer and enhance the electro-active areas. The linear range of detecting DA was from 6.82×10−8 to 4.98×10−2M and limit of detection (LOD) was 2.07×10−8M (S/N=3). The linear range of detecting UA was from 1.25×10−7 to 8.28×10−2M and LOD was 4.07×10−8M (S/N=3). The sensor was applied for the detection of DA and UA in human serum with good results. The sensor suggested that 3D metal-GO nanocomposites were superior materials for the fabrication of novel electrochemical sensors.

Synergistic electrocatalytic effect of nanostructured mixed films formed by functionalised gold nanoparticles and bisphthalocyanines

A synergistic electrocatalytic effect was observed in sensors where two electrocatalytic materials (functionalized gold nanoparticles and lutetium bisphthalocyanine) were co-deposited using the Langmuir–Blodgett technique. Films were prepared using a novel method where water soluble functionalised gold nanoparticles [(11-mercaptoundecyl)tetra(ethylene glycol)] (SAuNPs) were inserted in floating films of lutetium bisphthalocyanine (LuPc2) and dimethyldioctadecylammonium bromide (DODAB) as the amphiphilic matrix. The formation of stable and homogeneous mixed films was confirmed by π-A isotherms, BAM, UV–vis and Raman spectroscopy, as well as by SEM and TEM microscopy. The synergistic effect towards hydroquinone of the electrodes modified with LuPc2:DODAB/SAuNP was characterised by an increase in the intensity of the redox peaks and a reduction of the overpotential. This synergistic electrocatalytic effect arose from the interaction between the SAuNPs and the phthalocyanines that occur in the Langmuir–Blodgett films and from the high surface area provided by the nanostructured films. The sensitivity increased with the amount of LuPc2 and SAuNPs inserted in the films and limits of detection in the range of 10−7molL−1 were attained.

Synergistic electrocatalytic effect of graphene/nickel hydroxide composite for the simultaneous electrochemical determination of ascorbic acid, dopamine and uric acid

A novel solar graphene-nickel hydroxide modified glassy carbon electrode was developed and used for the simultaneous detection of ascorbic acid (AA), dopamine (DA) and uric acid (UA). The sensor exhibited appreciable electrocatalytic effect for the simultaneous detection of lower concentrations of the analytes compared to solar graphene modified glassy carbon electrode. The detection limits attained by differential pulse voltammetry (DPV) were 30μM, 120nM and 0.46μM for AA, DA and UA respectively. Recovery values ranging from 98 - 104% were obtained for the analysis of real samples.

Assembly of multi-walled carbon nanotubes–ZnSe quantum dot hybrids for a paeonol electrochemical sensor

Hybrid materials formed from acid functionalized multi-walled carbon nanotubes (MWCNTs) and glutathione (GSH)-capped ZnSe quantum dots (ZnSe QDs) were prepared by a non-covalent self-assembly method. Black spots decorated on the surface of MWCNTs under transmission electron microscopy (TEM) demonstrate successful attachment of ZnSe QDs on the surface of MWCNTs. The obtained ZnSe QD–MWCNTs can accelerate greatly the transfer rate of electrons and showed an obvious synergistic electrocatalytic effect for the oxidation of paeonol (PN). Based on this electrocatalytic activity, a novel electrochemical sensor was established. Under the optimum conditions, the peak currents had a good linear relationship with the concentration of PN in the ranges of 0.06 to 10.0 μM and 10.0 to 50.0 μM. The detection limit was reduced at 0.04 μM. The established sensing platform was applied to the determination of PN in pharmaceutical and clinical analyses with satisfactory recoveries.

A novel composite film derived from cysteic acid and PDDA-functionalized graphene: Enhanced sensing material for electrochemical determination of metronidazole

A novel composite film derived from cysteic acid and poly(diallydimethylammonium chloride)-functionalized graphene (PDDA-GN) was employed as an enhanced electrode material for ultrasensitive determination of metronidazole. The cysteic acid/PDDA-GN composite film was prepared by the electrochemical grafting of cysteic acid onto the PDDA-GN coated glassy carbon electrode (GCE). The cyclic voltammetry investigations reveal that the peak current of metronidazole reduction at the cysteic acid/PDDA-GN/GCE was remarkably enhanced compared to the bare GCE, the cysteic acid/GCE and the PDDA-GN/GCE. This result implies the synergistic electrocatalytic effect of cysteic acid and PDDA-GN. The fabricated sensor shows linear response to metronidazole in the ranges of 10nM–1μM and 70μM–800μM, with a detection limit of 2.3nM (S/N=3). The heterogeneous electron transfer rate constant and the diffusion coefficient of metronidazole were further evaluated by rotating disk electrode experiments. Moreover, we applied the present method to the determination of metronidazole in urine and lake water with satisfactory results.

Fabrication of polyphenol biosensor based on laccase immobilized on copper nanoparticles/chitosan/multiwalled carbon nanotubes/polyaniline-modified gold electrode

A high-performance amperometric polyphenol biosensor was developed, based on covalent immobilization of Ganoderma sp. laccase onto copper nanoparticles (CuNP's)/chitosan (CHIT)/carboxylated multiwalled carbon nanotube (cMWCNT)/polyaniline (PANI)-modified gold (Au) electrode. The CuNP's and cMWCNT had a synergistic electrocatalytic effect in the matrix of CHIT. The biosensor showed optimum response at pH 6.0 (0.1 M acetate buffer) and 35°C, when operated at 50 mVs(-1). The biosensor exhibited excellent sensitivity (the detection limit was down to 0.156 μM for guaiacol), fast response time (less than 4s) and wide linear range (from 1 to 500 μM). Analytical recovery of added guaiacol was 96.40-98.46%. Within batch and between batch coefficients of variation were <2.6% and <5.3%, respectively. The enzyme electrode was used 300 times over a period of 7 months, when stored at 4°C.

Comparative Studies of Electrochemical Behaviors of Benzenediols at a Gold Nanoparticle/carbon Nanotube Composite Modified Glassy Carbon Electrode

A gold nanoparticle/carbon nanotube composite modified glassy carbon electrode was fabricated and used to investigate electrochemical characteristics of hydroquinone, catechol, and resorcinol via cyclic voltammetric analysis under neutral pH conditions. The results imply that the gold nanoparticle/carbon nanotbue modified electrode exhibited a synergistic and excellent electrocatalytic effect of gold nanoparticles and carbon nanotube on the redox behaviors of benzenediols. The reversibility of electrochemical reaction was improved greatly and the peak currents were increased significantly compared with a bare electrode. Good linear relationships were obtained between the oxidation peak currents and the concentrations of catechol and resorcinol. The electrochemical process of catechol was controlled by surface adsorption process, while that of resorcinol was controlled by diffusion process. However, the peak current and the concentration of hydroquinone were not proportional in the whole concentration range, which is because the controlling process of electrochemical reactions was different in the different hydroquinone concentration. Benzenediols could be detected simultaneously at the modified electrode but not at the bare electrode. The stability of the modified electrode was excellent in the benzenediols solutions, which made it possible for the practical application of the modified electrode.

Hybrid gold atomic cluster–cobalt oxide scaffolds for dual tandem electrocatalytic sensing of cysteine

Innovations in nanoelectrochemistry have opened a plethora of techniques for the preparation of nanometer sized electrochemical probes with tunable properties. Atomic clusters emerged at the crossroad of physics and chemistry has immense potential as novel “electron antennaes” in electrocatalysis. Herein, we report the electrochemical synthesis and the synergistic electrocatalytic effect of metal oxide supported gold atomic clusters for subnanomolar level sensing of cysteine. The developed gold atomic clusters and the hybrid materials were characterized by spectral, morphological and electrochemical methods. Comparative evaluation of the critical role of surfactants in stabilizing the hybrid material and the mechanistic aspects of support scaffolds has been discussed. Different complexing agents were sequentially screened in order to get the optimum electrolyte composition for developing a uniform, reproducible sensing film. The developed modified electrode exhibits highly reproducible wider calibration range of 10 −10 to 10 −6 M with lower detection limits of 1.6 × 10 −11 M for cysteine. To gain a greater understanding of such advantageous behavior achieved with this electrode, studies on electrode kinetics of charge-transfer processes were also done.

Electrochemical behavior of methyl parathion and its sensitive determination at a glassy carbon electrode modified with ordered mesoporous carbon

Ordered mesoporous carbon (OMC) was synthesized and used to modify the surface of a glassy carbon (GC) electrode. Due to the unique properties of OMC, a decrease in the overvoltage of the reduction potential of methyl parathion (MP) (to ca. 219 mV) and a 76-fold increase in the peak current are observed (compared with a bare GC electrode). The absorption capacity of the surface of the electrode for MP was determined by chronocoulometry. The results show that the Г value of the modified electrode (2.34 × 10–9 mol cm–2) is 9.5 times as large as that of the GC electrode (2.47 × 10–10 mol cm–2). The new electrode exhibits synergistic electrocatalytic and accumulative effects on MP. MP can be determined by linear sweep voltammetry (LSV) which displays a linear relationship between peak current and MP concentration in the range from 0.09 to 61 μM, with a detection limit as low as 7.6 nM (at an S/N of 3) and after an accumulation at 0 V for 5 min. The electrode was successfully applied to the determination of MP in spiked lake water samples.

Prussian Blue Electrodeposited on Nano Ag-coated Multiwalled Carbon Nanotubes Composite for the Determination of Hydrogen Peroxide

A prussian blue (PB) electrodeposited on nano Ag-coated multiwalled carbon nanotubes (nano Ag-MWNTs) was reported. Also a PB/nano Ag-MWNTs composite modified glass carbon (GC) electrode was used to investigate the electrochemical behavior concerning the reduction of hydrogen peroxide. The experiment results showed that the PB/nano Ag-MWNTs/GC electrode had a wide linear range, a fast response time and high sensitivity toward the electrocatalytic reduction of hydrogen peroxide. PB and nano Ag-MWNTs had a synergistic electrocatalytic effect toward the reduction of hydrogen peroxide. The PB/nano Ag-MWNTs/GC electrode exhibited a wide linear response range of 8 x 10(-8) to 5 x 10(-3) mol/L with a correlation coefficient of 0.998 for the detection of hydrogen peroxide. Also the response time, detection limit (S/N = 3) and sensitivity of the PB/nano Ag-MWNTs/GC electrode were respectively determined to be 2 s, 4 x 10(-8) mol/L and 920 A/mol cm(2). Another attractive characteristic was that the PB/nano Ag-MWNTs/GC electrode showed high stability and reproducibility.

Immobilization-free direct electrochemical detection for DNA specific sequences based on electrochemically converted gold nanoparticles/graphene composite film

A direct electrochemical DNA sensor was constructed based on gold nanoparticles/graphene film. A precursor graphene film was fabricated on glassy carbon electrode (GCE) using both electrochemically reduced graphene oxide (ERGNO) and chemically reduced graphene oxide (CRGNO). The electrochemical approach was green and fast, and unlike chemical reduction, does not result in contamination of the reduced material, and at highly negative potential could reduce the oxygen functionalities (–OH, C–O–C and –COOH) of the graphene oxide more efficiently. ERGNO exhibited better electrochemical and electrocatalytic performances than CRGNO. Gold nanoparticles (AuNPs) were electrodeposited on the ERGNO/GCE to amplify the electrochemical signals. The resulting AuNPs/ERGNO composite film was characterized by scanning electron microscopy, energy dispersive spectroscopy and Raman spectroscopy. The electrochemical responses of guanine (G), adenine (A), thymine (T) and cytosine (C) were investigated at AuNPs/ERGNO/GCE, which showed more favorable electron transfer kinetics than at ERGNO/GCE, demonstrating the significantly synergistic electrocatalytic effect of ERGNO and AuNPs. Synthetic sequence-specific DNA oligonucleotides was successfully detected and the established immobilization-free biosensor had the ability to discriminate single- or double-base mismatched DNA.