Enhancement Of Electrocatalytic Activity Research Articles

Enhancement of Electrocatalytic Hydrogen Evolution Activity of Carbon Felt in Alkaline Media

Bu çalışmada, karbon keçe üzerine bakır, kobalt, kobalt-bakır ve kobalt/platin elektrokimyasal olarak çöktürülmüştür. Hazırlanan elektrotların 1 M KOH çözeltisinde hidrojen gazı çıkışına katalitik etkisi katodik akım-potansiyel eğrileri, elektrokimyasal impedans spektroskopisi (EIS) ve elektroliz yöntemleri kullanılarak incelenmiştir. Hazırlanan elektrotların zamanla kararlılık testi 1 M KOH çözeltisi içinde 2,2x10-3 A m-2’lik akım yoğunluğunda araştırılmıştır. Elde edilen sonuçlara göre karbon keçe üzerine, kobalt, kobalt-bakır ve kobalt/platin çöktürülmesi elektrotun aşırı gerilimini düşürerek hidrojen gazı çıkışını arttırmaktadır. Elektrotun katalitik etkinliği çöktürülen metalin türüne bağlıdır. Katalitik etkinliğin artması keçe elektrotun büyük yüzey alanı ve kobalt ile platinin yüksek katalitik etkinliği ile açıklanabilir.

Ultrasensitive determination of nalbuphine and tramadol narcotic analgesic drugs for postoperative pain relief using nano-cobalt oxide/ionic liquid crystal/carbon nanotubes-based electrochemical sensor

Pain is an important and complex protective phenomenon. Good postoperative pain relief is important as it alleviates patient suffering and aids a rapid, uncomplicated recovery. Narcotic analgesic drugs are a support in pediatric operation in this circumstance when a patient has “nothing per oral” status. A novel reliable electrochemical sensor is fabricated for direct and sensitive determination of nalbuphine (NB) and tramadol (TR) analgesic drugs based on cobalt oxide/ionic liquid crystal/carbon nanotubes modified carbon paste electrode in presence of sodium dodecyl sulfate (CNTILCCoCP-SDS). The effect of type of metal oxide on the catalytic activity of the sensor towards NB determination was evaluated. Nano‑cobalt oxide showed highest electro-catalytic activity, excellent conductivity, antifouling ability and charge transfer enhancement compared to other studied metal oxides. Under the optimized conditions, simultaneous determination of NB and TR in human urine using the proposed sensor was successfully achieved with sub-nano detection limits of 0.58nM and 0.62nM respectively. The practical analytical performance of the sensor was attained for determination of NB and TR in their pharmaceutical samples with satisfied recovery results. This sensor has great ability to be extended for electrochemical applications in assaying of many drugs.

Facile loading mesoporous Co3O4 on nitrogen doped carbon matrix as an enhanced oxygen electrode catalyst

A nanocomposite with mesoporous Co3O4 loaded on nitrogen-doped mesoporous carbon (Co3O4@NMC) has been constructed by a facile post-grinding process. The electro-catalytic experimental results show that Co3O4@NMC (1:3) can be regarded as the low-cost alternative ORR/OER bi-functional catalyst compared with commercial noble Pt/C + IrO2 catalysts. The potential difference (ΔE) between between E1/2 and Ej10 for Co3O4@NMC (1:3) sample is only 21 mV larger. Moreover, we observed no obvious degeneration in both ORR and OER activity during ADT tests. The enhancement of electro-catalytic activity can be attributed to the effective charge transfer process as suggested by the Tafel analysis due to the synergistic effect.

Anchoring gold nanoparticles on poly(3,4-ethylenedioxythiophene) (PEDOT) nanonet as three-dimensional electrocatalysts toward ethanol and 2-propanol oxidation

Renewable alcohol oxidation is of vital significance for clean energy conversion and storage. Here, we fabricated a three-dimensional (3D) nanonet-like hybrid catalyst combining Au nanoparticles and poly(3,4-ethylenedioxythiophene) (PEDOT) together, in which PEDOT nanonets act as the framework of the 3D catalyst and the support for the dispersion of Au nanoparticles. The catalyst was designated as Au-PEDOT. By using conductive carbon cloth (CC) as electrode substrates, the as-fabricated Au-PEDOT/CC electrodes were applied to evaluate the electrocatalytic activity towards ethanol and 2-propanol in the alkaline media, respectively. The catalytic activity on Au-PEDOT/CC in terms of the peak current and/or peak current density towards ethanol and 2-propanol oxidation is five times higher than that on comparative Au/CC catalysts, respectively, which is also higher than that on some similar materials reported in the literature. In addition, the Au-PEDOT/CC electrode also possessed great durability and reproducibility. This enhancement in electrocatalytic activity can be attributed to a number of factors: the nano-scale of the Au catalysts, the 3D nanostructure of the catalysts, the conductivity of PEDOT, as well as the effect of alkaline media. These results indicate the as-synthesized Au-PEDOT is a promising electrocatalyst for liquid fuel oxidation.

Ultrafine NiCoP-decorated N,S,P-codoped hierarchical porous carbon nanosheets as an efficient bifunctional electrocatalyst for oxygen reduction and oxygen evolution

Large-scaled NiCoP/NSP-HPCNS were fabricated by a facile pyrolysis method. Porous carbon nanosheets provided extra active sites easily available for reactants, and dramatically improved the stability. The nanocomposites displayed remarkable enhancement in electrocatalytic activity and durability for ORR and OER.

Nano-Au Catalysts Modified with TiO2: Enhancement of Electrocatalytic Activity for 1-Propanol Oxidation in Alkaline Media

Electrocatalytic activity of the anode for alcohols oxidation is a critical issue in fuel cell which is considered as a clean energy. Performance deterioration of the catalyst takes place due to the adsorption of carbonaceous residues on the electrode surface, which is also known as poisoning of the electrode. Desorption of carbonaceous residues is thought to be an essential solution but not has been studied systematically. In this work, we investigate both the desorption of carbonaceous residues and the promotion of electrocatalytic activity to alcohols oxidation reactions by using Au nanoparticles (NPs)-TiO2/polyaniline (PANI) composite to boost the overall activity of electrocatalytic alcohol oxidation reactions. Desorption of carbonaceous residues and electrocatalytic activity of alcohol oxidation reactions are evaluated by cyclic voltammetry (CV) measurements in various alcohols. The chronoamperometric i-t curves are measured to evaluate the stability. Mechanisms for desorption of carbonaceous residues and enhancement of the electrocatalytic activity are elaborated and summarized. Electrodes with TiO2 decoration show better performance than TiO2-free specimens. In addition, Au NPs-decorated composites not only show an extra characteristic peak of alcohol oxidation reactions but also perform a constructive effect on the already existing oxidation reaction, indicating the promotion of electrocatalytic oxidation of alcohols.

Synthesis of nitrogen-doped mesoporous carbon nanosheets for oxygen reduction electrocatalytic activity enhancement in acid and alkaline media

In the present work, nitrogen-doped mesoporous carbon nanosheets (NMCNs) are prepared and extensively investigated for the oxygen reduction reaction. Initially, by using dual templates, viz. graphene oxide and a cationic surfactant, silica films (thickness: 1.0 nm) are synthesized and characterized using transmission electron microscope (TEM), nitrogen adsorption-desorption (N2 ad/des) measurements, and small-angle X-ray diffraction (SA-XRD).Morphology and structure of silica evolve along with graphene oxide concentration, while the co-operative assembly and the final structure are determined by the electrostatic interaction between the dual templates. The effect of silica template on the resultant NMCNs is investigated physicochemically by photoelectron spectroscopy (XPS), TEM, N2 ad/des and electrochemically by cyclic voltammetry (CV), and linear sweep voltammetry (LSV).NMCNs are featured of a high content of nitrogen dopant, high specific surface area (SSA) and ultrathin thickness (1.5 nm), favoring catalysis and facilitating the mass transport of the reactive species. From the electrochemical tests, it is confirmed that NMCNs yield a high oxygen reduction reaction (ORR) electrocatalytic activity in acid and alkaline environment; this activity is similar or even better as compared with the one measured over carbon supported platinum commercial catalyst (40 wt % Pt/C).

Unraveling the composition-activity relationship of Pt[sbnd]Ru binary alloy for hydrogen oxidation reaction in alkaline media

The research and development of hydrogen oxidation reaction catalysts in alkaline media is a prerequisite for the commercialization of alkaline polymer electrolyte fuel cell. PtRu bimetallic catalyst was found to be more active towards HOR than Pt in alkaline, but the composition-activity relationship of PtRu alloys is still lacking. Herein, a series of PtRu alloy planar electrodes with 14 different compositions were prepared in a high-throughput fashion using an improved magnetron sputtering method. The atomic ratio of Pt was controlled from 6.7% to 99.7% within the samples. The corresponding electro-catalytic activities towards the HOR in alkaline were systematically measured by rotating disc electrode method. A volcano-shape relationship between the HOR exchange current density and the Ru atomic fraction was revealed, and maximum activity was observed at ca. 55% content of Ru. The enhancement in electro-catalytic activity is attributed to a reduction in the electronic charge density of Pt upon Ru doping.

Towards activation of amorphous MoSx via Cobalt doping for enhanced electrocatalytic hydrogen evolution reaction

Amorphous molybdenum sulfide (a-MoSx) has been shown as one of the most promising catalysts in acidic electrolytes towards hydrogen evolution reaction (HER). Its intrinsic electrocatalytic activity can be further enhanced via doping and cropping the electronic structure.In this study, one-step electro-deposition was employed to fabricate MoSxCoy/TNAs hybrid electrodes using TiO2 nanotube arrays as support. The microstructure and chemical composition of the samples were characterized via X-ray diffraction (XRD), scanning electron microscope (SEM), tunneling electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopy (EDS). The electrochemical properties of the samples were investigated through linear sweep voltammetry (LSV), cyclic voltammetry (CV), Tafel curves, and electrochemical impedance spectroscopy (EIS). According to experimental results, MoSCo structure was formed after Co2+ was incorporated into MoSx, resulting in increases in both unsaturated Mo and S atoms acting as the active sites that lead to enhancement of intrinsic electrocatalytic activity. The pseudo-capacitance of MoSxCoy/TNAs (x = 1.70, y = 0.25) reached 46 mF cm−2, a 31.4% improvement over 35 mF cm−2 of MoSx/TNAs. The onset hydrogen evolution potential, overpotentials at current densities of −10 mA cm−2 and –20 mA cm−2 were recorded at −92 mV, −173 mV, and −209 mV, respectively, reduction of 30 mV, 24 mV, and 28 mV than −112 mV, −197 mV, and −237 mV of MoSx/TNAs, respectively. This electrode was subjected to 1000-cycle testing and demonstrated stable electrochemical activity, illustrating excellent stability.

Activated Cu/Cu2O foam with Ni nanoparticles for electrocatalytic activity enhancement of hydrogen evolution reaction (HER) in acidic media

This paper presents the hydrogen evolution reaction of Cu/Cu2O foam by Ni nanoparticles, deposited by electrodeposition and electroless plating. The structure and morphology of Cu/Cu2O foam and deposited Ni nanoparticles were studied by FE-SEM and XRD. The foam with Ni nanoparticles had a high specific surface area measured by BET. The synthesized Cu/Cu2O foam/Ni electrode presented high electrocatalytic activity for HER, with low overpotential of −290mV vs. Ag/AgCl and Tafel slope of 50mVdecade−1. The stability study of the developed electrodes showed a high stability in short-term.

Enhancement of Electrocatalytic Oxygen Reduction Activity and Durability of Pt-Ni Rhombic Dodecahedral Nanoframes by Anchoring to Nitrogen-Doped Carbon Support.

Pt-based nanostructured electrocatalysts supported on carbon black have been widely studied for the oxygen reduction reaction (ORR), which occurs at the cathode in polymer electrolyte fuel cells. Because sluggish ORR kinetics are known to govern the cell performance, there is a need to develop highly active and durable electrocatalysts. The ORR activity of Pt-based electrocatalysts can be improved by controlling their morphology and alloying Pt with transition metals such as Ni. Improving the catalyst durability remains challenging and there is a lack of catalyst design concepts and synthetic strategies. We report the enhancement of the ORR activity and durability of a nanostructured Pt–Ni electrocatalyst by strong metal/support interactions with a nitrogen-doped carbon (NC) support. Pt–Ni rhombic dodecahedral nanoframes (NFs) were immobilized on the NC support and showed higher ORR electrocatalytic activity and durability in acidic media than that supported on a nondoped carbon black. Durability tests demonstrated that NF/NC showed almost no activity loss even after 50 000 potential cycles under catalytic conditions, and the Ni dissolution from the NFs was suppressed at the NC support, as confirmed by energy dispersive X-ray spectroscopy analysis. Physicochemical measurements including surface-enhanced infrared absorption spectroscopy of surface-adsorbed CO revealed that the strong metal/support interactions of the NF with the NC support caused the downshift of the d-band center position of the surface Pt. Our findings demonstrate that tuning the electronic structure of nanostructured Pt alloy electrocatalysts via the strong metal/support interactions with heteroatom-doped carbon supports will allow the development of highly active and robust electrocatalysts.

Microwave-assisted polyol preparation of reduced graphene oxide nanoribbons supported platinum as a highly active electrocatalyst for oxygen reduction reaction

Reduced graphene oxide nanoribbons (RGONRs) supported platinum catalysts were prepared by microwave-assisted polyol method, in which Pt nanoparticles were uniformly dispersed with a mean particle of 3.5 nm. During the synthesis, Pt ions were first attached to graphene oxide nanoribbons, then the encased metal ions and graphene oxide nanoribbons were simultaneously reduced by ethylene glycol. X-ray photoelectron spectra and X-ray diffraction indicate that the graphene oxide nanoribbons were partially reduced and the Pt nanoparticles were attached to the oxygen-containing groups on the surface of the support. Pt/RGONRs exhibits excellent activity for the oxygen reduction reaction, which is approximately 2 times better than commercial Pt/C with promising durability after 5000 cycles of accelerated durability tests. The enhancement of electrocatalytic activity and better durability may be explicated by the well dispersed Pt NPs on the RGONRs and the attachment of Pt ions with the oxygen-containing groups before the reduction. Reduced graphene oxide nanoribbons supported platinum catalyst (Pt/RGONRs) were prepared by microwave-assisted polyol method, which exhibited good electroactivity and promising stability toward the oxygen reduction reaction.

Photocatalysis an enhancer of electrocatalytic process

Summary The phenomenon to restrain electrocatalytic particle agglomeration, while boosting the activity of multi-electron charge transfer reactions, known as strong-metal support-interaction, is reviewed. The main insights of this phenomenon are outlined. In this respect, the connection of a photo-induced process, to anchor metal centers, contributes to the electrocatalytic activity enhancement. Selected examples are given.

Oxygen reduction and hydrogen oxidation reaction on novel carbon supported PdxIry electrocatalysts

In the present work Vulcan XC-72 carbon supported Pd, Ir and PdxIry (with x:y atomic ratios of 3:1, 1:1, 1:3) electrocatalysts are thoroughly investigated for the reactions of hydrogen oxidation (HOR) and oxygen reduction (ORR). The catalysts are prepared via a pulse-microwave assisted polyol synhtesis method. The techniques of X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) are adopted to investigate the elemental composition, the structure, and the morphology of the as prepared electrocatalysts.Their electrocatalytic properties toward HOR and ORR are evaluated by the aid of cyclic voltammetry (CV) and rotating disk electrode (RDE) techniques. It is found that after the addition of even a small amount of iridium, the electrocatalytic activity of pure palladium is enhanced toward both reactions.According to the obtained results the highest HOR and ORR electrocatalytic activity enhancement is exhibited by PdIr (1:1) sample. The order of the electrocatalytic activity is found to be PdIr > PdIr3 > Pd3Ir > Pd > Ir for HOR and PdIr > Pd3Ir > PdIr3 > Pd > Ir for the ORR, respectively.

Self-assembled CNT/Ni0.85Se-SnO2 networks as highly efficient and stable electrocatalyst for hydrogen evolution reaction

For the first time, a novel porous and conductive Ni0.85Se-based electrocatalyst, CNT/Ni0.85Se-SnO2 networks (CNSN), has been synthesized utilizing a facile solvothermal method. The CNSN exhibit much better hydrogen evolution reaction (HER) performance than bare Ni0.85Se-SnO2 nanoparticles (NSP) and bare Ni0.85Se, with ultra-low Tafel slope of 33.2 mV dec−1, which is comparable to that of commercial Pt/C electrocatalysts, a large cathode current density of 28.4 mA cm−2 (at ∼ −270 mV vs RHE), which is over 4 and 10 times larger than those of NSP (7.1 mA cm−2), and bare Ni0.85Se (2.7 mA cm−2), respectively. It also shows outstanding electrocatalytic stability even after 1500 CV cycles. The superior HER performances of CNSN can be attributed to its well-designed unique nanoarchitecture with high conductivity and rich porosity. Ni0.85Se-SnO2 nanoparticles are anchored on the porous networks constructed with highly conductive CNT, and adjacent Ni0.85Se-SnO2 nanoparticles are tightly connected to each other. As a result, it can not only guarantee strong reactive activity and abundant active sites due to its large specific surface area and rough surface, but also facilitate the charge transfer, resulting in the enhancement of electrocatalytic activity and stability. This work provides a rational structural design and a low-cost, facile synthesis method of transition-metal chalcogenide based electrocatalysts with good stability and high efficiency for hydrogen evolution reaction.

Ni-Se nanostructrures dependent on different solvent as efficient electrocatalysts for hydrogen evolution reaction in alkaline media

Different Ni-Se nanostructures are in situ prepared based on Ni foam (NF) through facile hydro(solvo)thermal selenization process under different solvents including ethanol, N, N-dimethylformamide (DMF) and water. The as-prepared Ni-Se/NF samples demonstrate different phase, composition and surface morphology through physical characterization. XRD and SEM indicate that Ni-Se growing in water demonstrates mixed crystal phases of NiSe and Ni3Se2 with nanorod-like nanostructures, whereas samples Ni-Se prepared in DMF and ethanol are pure NiSe phase with nanoneedle-like nanostructures. Electrocatalytic activity for hydrogen evolution reaction (HER) of all samples has been evaluated in alkaline solution. NiSe/NF (ethanol) demonstrates the smallest overpotential (170.5 mV) to reach j = −10 mA cm−2 for HER and excellent long-term stability. The enhancement of electrocatalytic activity in alkaline solution may be ascribed to its good conductivity and large electrochemically active surface area (ECSA).

Enhancement of Durability and Electrocatalytic Activity of Pt/C via CTAB-Modified Ultrathin Mesoporous Silica Coating for Methanol Oxidation

An ultrathin mesoporous silica layer was directly coated onto Pt/C (Pt/C@mSiO2) using a cetyltrimethyl ammonium bromide (CTAB)-modified Stöber method without introducing an intermediate layer. The stability of the synthesised Pt/C@mSiO2 was evaluated by the accelerated potential cycling test (APCT). The electrochemically active surface area (ECSA) of the Pt/C@mSiO2 remained at 90 % while the ECSA of the Pt/C decreased to 51 % after APCT. Transmission electron microscopy images of the Pt/C and the Pt/C@mSiO2 before and after APCT suggest the silica coating effectively suppressed Pt aggregation. Furthermore, the Pt/C@mSiO2 exhibited higher electrocatalytic activity for methanol oxidation reaction than Pt/C.

Activating electrochemical catalytic activity of bio-palladium by hybridizing with carbon nanotube as \u201ce\u2212 Bridge\u201d

Nano metal catalysts produced by bacteria has received increasing attention owing to its environmental friendly synthesis route. However, the formed metal nanoparticles are associated with poorly conductive cells and challenged to be electrochemically applied. In this study, Palladium (Pd) nanoparticles were synthesized by Shewanella oneidensis MR-1. We demonstrated the limitation of palladized cells (Pd-cells) serving as electro-catalysts can be relieved by hybridizing with the conductive carbon nanotubes (Pd-cells-CNTs hybrid). Compared to the Pd-cells, the electrochemical active surface area of Pd in Pd-cells-CNTs10 (the ratio of Pd/CNTs is 1/10 w/w) were dramatically increased by 68 times to 20.44 m2·g−1. A considerable enhancement of electrocatalytic activity was further confirmed for Pd-cells-CNTs10 as indicated by a 5-fold increase of steady state current density for nitrobenzene reduction at −0.55 V vs Ag/AgCl. These results indicate that the biogenetic palladium could has been an efficient electro-catalyst but just limited due to lacking an electron transport path (e− Bridge). This finding may also be helpful to guide the way to electrochemically use other biogenetic metal nano-materials.

Comparison of three nickel-based carbon composite catalysts for hydrogen evolution reaction in alkaline solution

In this work, preparing three nickel-based carbon composite catalysts (Ni-OCNT, Ni-ONC and Ni-rGO) by supergravity field electrodeposition for hydrogen evolution reaction (HER) from nickel sulfamate bath containing suspended nano-sized carbon materials. The crystal structure, morphology and chemical compositions of the composite catalysts were characterized by XRD and SEM measurements. The electrochemical activity of composite coatings for HER was determined by polarization measurement and electrochemical impedance spectroscopy in 1.0 M NaOH solution. The prepared nickel-based carbon composite catalysts exhibit a significant enhancement in electrocatalytic activity for HER compared with pure Ni electrode. In addition, the Ni-rGO, Ni-ONC, Ni-OCNT catalysts prepared under supergravity field demand overpotentials of 245, 177, 91 mV and 286, 224, 154 mV and 330, 286, 222 mV to drive current densities of 80, 30, 10 mA cm−2, respectively. Ni-rGO cathode presents excellent HER activity with lowest overpotentials.

La0.8Sr0.2MnO3-Based Perovskite Nanoparticles with the A-Site Deficiency as High Performance Bifunctional Oxygen Catalyst in Alkaline Solution.

Perovskite (La0.8Sr0.2)1-xMn1-xIrxO3 (x = 0 (LSM) and 0.05 (LSMI)) nanoparticles with particle size of 20-50 nm are prepared by the polymer-assisted chemical solution method and demonstrated as high performance bifunctional oxygen catalyst in alkaline solution. As compared with LSM, LSMI with the A-site deficiency and the B-site iridium (Ir)-doping has a larger lattice, lower valence state of transition metal, and weaker metal-OH bonding; therefore, it increases the concentration of oxygen vacancy and enhances both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). LSMI exhibits superior ORR performance with only 30 mV onset potential difference from the commercial Pt/C catalyst and significant enhancement in electrocatalytic activity in the OER process, resulting in the best oxygen electrode material among all the reported perovskite oxides. LSMI also exhibits high durability for both ORR (only 18 mV negative shift for the half-wave potential compared with the initial ORR) and OER process with 10% decay. The electrochemical results indicate that the A-site deficiency and Ir-doping in perovskite oxides could be promising catalysts for the applications in fuel cells, metal-air batteries, and solar fuel synthesis.