Ultrafine Fe3C nanoparticles embedded in N-doped graphitic carbon sheets for simultaneous determination of ascorbic acid, dopamine, uric acid and xanthine.

A pyrolytic method is described for preparation of ultrafine Fe3C nanoparticles incorporated into N-doped graphitic carbon nanosheets (Fe3C@NGCSs). Iron phthalocyanine and graphitic carbon nitride (g-C3N4) are used as starting materials. The hybrid nanocomposite was placed on a glassy carbon electrode (GCE) and then applied to simultaneous determination of ascorbic acid (AA), dopamine (DA), uric acid (UA) and xanthine (XA). Figures of merits are as follows: for AA, the linear response range covers the 54.0-5491.0 µM range, the lower detection limit is 16.7 µM, and the best working voltage (vs. the saturated calomel electrode (SCE)) is 0.05 V. The respective data for DA are 1.2-120.8 µM, 0.34 µM and 0.19 V (vs. SCE). For UA, the respective data are 4.8-263.0 µM, 1.4 µM and 0.32 V (vs. SCE), and for XA the data are 4.8-361.0 µM, 1.5 µM and 0.71 V (vs. SCE). The method was successfully applied to their simultaneous determination in spiked serum samples. Graphical abstract Ultrafine Fe3C nanoparticles embedded in N-doped graphitic carbon sheets for simultaneous determination of ascorbic acid, dopamine, uric acid and xanthine.

Facile synthesis of nanoflower-like phosphorus-doped Ni3S2/CoFe2O4 arrays on nickel foam as a superior electrocatalyst for efficient oxygen evolution reaction.

Developing cost-effectiveness and superior electrocatalysts is crucial to improve the efficiency of oxygen evolution reaction (OER) in water splitting system. Hence, flower-like phosphorus doped Ni3S2/CoFe2O4 arrays (P-Ni3S2/CoFe2O4/NF) were generated on three-dimensional (3D) nickel foam (NF) via the two-step hydrothermal treatment and subsequent phosphorization. Additionally, a series of control experiments were conducted to investigate the formation mechanism. By virtue of the unique 3D configurations and multi-compositions, the as-prepared catalyst exhibited greatly improved OER performance in 1.0 M KOH solution, with the overpotential of only 254 mV at 50 mA cm-2 and low Tafel slope of 54.43 mV dec-1. This study provides a feasible approach for preparing advanced electrocatalyst in energy conversion and storage devices.

Walnut kernel-like iron-cobalt-nickel sulfide nanosheets directly grown on nickel foam: A binder-free electrocatalyst for high-efficiency oxygen evolution reaction.

Developing earth-rich and high-efficiency nonprecious metal catalysts is critical but extremely challenging for oxygen evolution reaction (OER). Herein, a simple room-temperature sulfuration method was developed for in situ synthesis of walnut kernel-like iron-cobalt-nickel sulfide nanosheets on nickel foam (FeCoNiSx/NF). The unique nanosheets exposed abundant active sites and provided large electrochemically active surface area. The as-built FeCoNiSx/NF exhibited high OER performances with the small overpotentials of 231 and 268 mV to afford 10 and 50 mA cm-2 in 1.0 M KOH, respectively, coupled with a small Tafel slope of 55 mV dec-1. Furthermore, the FeCoNiSx/NF acted as the anode towards overall water electrolysis with acceptable results, where commercial Pt/C dropped on the NF worked as the cathode. This study provides some valuable insights for rational construction of nonprecious electrocatalysts in electrochemical energy technologies.

Iron, manganese co-doped Ni3S2 nanoflowers in situ assembled by ultrathin nanosheets as a robust electrocatalyst for oxygen evolution reaction.

Exploring high-performance and stable transition metal electrocatalysts is prerequisite for boosting overall water splitting efficiency. In this study, iron (Fe), manganese (Mn) co-doped three-dimensional (3D) Ni3S2 nanoflowers were in situ assembled by many inter-connected 2D nanosheets on nickel foam (NF) via hydrothermal and sulfuration treatment. By virtue of the introduced Fe and Mn elements and unique flower-like structures, the as-prepared catalyst displayed high activity and stability for oxygen evolution reaction (OER), coupled with a small Tafel slope (63.29 mV dec-1) and a low overpotential of 216 mV to reach the current density of 30 mA cm-2. This study would shed some lights for facile synthesis of exceptional OER catalyst by tailoring the electronic structure and doping transition metal(s).

Trimetallic PtRhCo petal-assembled alloyed nanoflowers as efficient and stable bifunctional electrocatalyst for ethylene glycol oxidation and hydrogen evolution reactions.

Controllable synthesis of multimetal nanocrystals with hierarchical structures and tunable compositions are feasible to steeply improve the catalytic properties in fuel cells. Herein, trimetallic PtRhCo petal-assembled alloyed nanoflowers (PtRhCo PAANFs) were fabricated via a one-pot solvothermal method, which showed remarkable enlargement in specific activity and mass activity over PtRh0.25Co nanodentrites (NDs), PtRh1.5Co NDs, PtCo NDs and commercial Pt/C catalysts for ethylene glycol oxidation in 0.5 M KOH solution. The as-developed catalyst exhibited dramatically better CO tolerance and recoverability, coupling with the superior activity and durability for hydrogen evolution reaction (HER) in the alkaline electrolyte. This work demonstrates the significance of Rh in the alloy for improving the stability. This work offers a promising strategy for preparation of advanced trimetallic electrocatalysts for energy conversion applications.

Porous dendritic PtRuPd nanospheres with enhanced catalytic activity and durability for ethylene glycol oxidation and oxygen reduction reactions.

Developing highly active and durable catalyst is of pivotal importance in fuel cells, owing to excessive consumption of fossil fuels. Herein, porous dendritic PtRuPd nanospheres (PtRuPd NSs) were synthesized by a facile hexadecylpyridinium chloride (HDPC)-mediated one-pot aqueous method with ascorbic acid (AA) as the reducing agent. The as-obtained PtRuPd NSs displayed high-efficient catalytic activity and durability for ethylene glycol oxidation reaction (EGOR) and oxygen reduction reaction (ORR). It exhibited enlarged mass activity (MA, 1.368 A mg-1) compared to commercial Pt/C (1.100 A mg-1) for EGOR. Besides, the onset potential (Eonset, 0.930 V) and half-wave potential (E1/2, 0.852 V) of PtRuPd NSs were more positive relative to homemade PtPd NSs (0.905 and 0.840 V), PdRu NSs (0.895 and 0.839 V), and commercial Pt/C (0.910 and 0.822 V) toward ORR. This work provides some valuable guidelines for producing novel trimetallic nanocatalysts in fuel cells.

One-pot aqueous synthesis of two-dimensional porous bimetallic PtPd alloyed nanosheets as highly active and durable electrocatalyst for boosting oxygen reduction and hydrogen evolution.

Recently, two-dimensional materials have gained increasing research attention due to their large surface area, high physical and chemical stability, and excellent electrocatalytic performances. Herein, we reported a simple and fast one-pot aqueous method for synthesis of two-dimensional porous bimetallic PtPd alloyed nanosheets (NSs) using benzyldimethylhexadecylammonium chloride (HDBAC) as the capping agent and stabilizer. The formation mechanism involved the oriented attachment and self-assembly. The PtPd NSs exhibited excellent oxygen reduction reaction (ORR) activity with the positive shift (c.a. 43 mV) of the half-wave potential in 0.1 M KOH solution, clearly outperforming that of commercial Pt/C (50 wt%). Moreover, the as-prepared catalyst displayed 2.4 times enlargement in mass activity (MA, 382.10 mA mg-1) and 3.5 times enhancement in specific activity (SA, 0.95 mA cm-2) relative to those of Pt/C at 0.80 V. Meanwhile, the as-obtained catalyst demonstrated highly boosted hydrogen evolution reaction (HER) in 0.5 M H2SO4 electrolyte, surpassing that of Pt/C. These results reveal the practical applications of the catalyst in energy storage and conversion.

One-pot solvothermal synthesis of three-dimensional hollow PtCu alloyed dodecahedron nanoframes with excellent electrocatalytic performances for hydrogen evolution and oxygen reduction.

It is a great challenge to develop simple approach to construct three-dimensional (3D) bimetallic alloyed nanoframes (NFs) with tunable surface structures, albeit with the availability of noble metal NFs in catalysis. Herein, a one-pot solvothermal method was employed for scalable preparation of uniform hollow PtCu rhombic dodecahedron nanoframes (PtCu RDNFs) in the presence of cetyltrimethylammonium chloride (CTAC), where diglycolamine (DGA) served as the co-reductant and co-structure director. The above architectures had the larger electrochemically active surface area (ECSA, 36.85 m2 g-1Pt) than that of commercial Pt black (15.85 m2 g-1Pt), along with the improved catalytic characters for hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) in acid electrolytes alternative to those of Pt black. It demonstrates great potential applications of PtCu RDNFs in fuel cells and beyond.

Graphene-encapsulated cobalt nanoparticles embedded in porous nitrogen-doped graphitic carbon nanosheets as efficient electrocatalysts for oxygen reduction reaction.

Transition metal and nitrogen (N) doped carbon materials are regarded as promising alternatives to expensive Pt-based catalysts for oxygen reduction reaction (ORR), thanks to their natural abundance, good stability and high energy conversion efficiency. Herein, a facile efficient pyrolysis approach was developed to prepare graphene-encapsulated Co nanoparticles (NPs) embedded in porous nitrogen-doped graphitic carbon nanosheets (Co@G/N-GCNs), in which g-C3N4 served as C and N sources, and cobalt phthalocyanine (CoPc) as the Co- and N-sources. The as-obtained catalyst exhibited exceptional ORR activity (E1/2 = 0.86 V vs. RHE), good durability (12 mV negative shift of E1/2 after 2000 cycles), and strong methanol resistance, surpassing those of commercial Pt/C catalyst in alkaline conditions. The pyrolysis temperature and entrapped contents of metal NPs had critical impacts on the ORR features. This work offers a feasible strategy for designing low-cost non-noble-metal catalysts for energy storage and conversion.

A simple wet-chemical strategy for facile fabrication of hierarchical PdAu nanodentrites as excellent electrocatalyst for oxygen reduction reaction.

Herein, a simple one-pot wet-chemical method was presented for facile preparation of three-dimensional (3D) PdAu nanodentrites (NDs) containing plenty of local high-index and low-index facets at room temperature, adopting 3-amino-1,2,4- triazole-5-carboxylic acid (ATCA) as the structure-guiding agent, without any seed or surfactant. The feeding ratios of the Pd/Au precursors, the concentration of ATCA and the presence of ascorbic acid (AA) have great effects on the PdAu nanostructures. The as-prepared PdAu NDs exhibited dramatically enhanced catalytic properties towards oxygen reduction reaction (ORR) under the alkaline conditions, showing the more positive half-wave potential (0.890 V) relative to commercial Pd black (0.808 V), coupled with the 8.3-fold enlargement in mass activity (MA). This study developed a simple and straightforward approach to prepare advanced PdAu electrocatalysts in fuel cells.

Graphene wrapped Fe7C3 nanoparticles supported on N-doped graphene nanosheets for efficient and highly methanol-tolerant oxygen reduction reaction.

Green and efficient non-precious metal electrocatalysts for oxygen reduction reaction (ORR) are prepared to meet the increasing demand for clean, secure and sustainable energy. Herein, we report a novel and environmentally friendly strategy for synthesis of graphene-wrapped iron carbide (Fe7C3) nanoparticles supported on hierarchical fibrous N-doped graphene with open-mesoporous structures (Fe7C3/NG) by simply annealing the mixture of melamine, iron (II) phthalocyanine (FePc) and Fe2O3. The effects of the pyrolysis temperature and the molar ratio of FePc to melamine were critically examined in the controls. Remarkably, the Fe7C3/NG obtained at 800 °C (i.e. Fe7C3/NG-800) manifested the forward shifts in the onset potential (0.98 V) and half-wave potential (0.85 V) with respective to commercial Pt/C (50 wt%) in 0.1 M KOH, coupled with the great enhancement in the durability (still remained 92.11% of its initial current density even after 40,000 s) and strong methanol tolerance. This research presents a promising strategy for developing Pt-free non-precious efficient ORR electrocatalysts in fuel cells.

Hollow Ag44Pt56 nanotube bundles with high electrocatalytic performances for hydrogen evolution and ethylene glycol oxidation reactions.

It is a main challenge to synthesize highly efficient and durable nanocatalysts towards hydrogen evolution reaction (HER) and alcohol oxidation reaction in energy conversion and storage. Herein, a green wet-chemical approach was developed to directly prepare hollow Ag44Pt56 nanotube bundles (H-Ag44Pt56 NTBs), utilizing 5-azacytosine as a structure-directing agent. The obtained electrocatalyst displayed superior catalytic activity and durability for HER in acid media, and the great improvement in catalytic performance for ethylene glycol oxidation reaction (EGOR) in the alkaline electrolyte, outperforming home-made Ag34Pt66 nanoparticles (NPs), Ag70Pt30 NPs, and commercial Pt/C catalysts. The high electrocatalytic characters are mainly attributed to the special nanostructures and the synergetic effects between the bimetals.

Facile synthesis of prickly platinum-palladium core-shell nanocrystals and their boosted electrocatalytic activity towards polyhydric alcohols oxidation and hydrogen evolution.

Herein, prickly platinum-palladium core-shell nanocrystals (Pt@Pd NCs) were prepared by a facile one-pot aqueous method, only taking sodium pyrrolidone carboxylate (PCA-Na) as the structure director and stabilizing agent. The products were mainly characterized by microscopic analysis, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), followed by discussing the formation mechanism in details. The electrochemical characterizations were examined by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry (CA). The results revealed that the prepared architectures had the biggest current density (58.4 mA cm-2) for ethylene glycol oxidation, which is 3.5-fold, 1.2-fold, 2.3-fold and 2.4-flod enhancement relative to those of home-made single Pt nanoparticles (NPs) and Pd NPs, commercial Pt black and Pd black catalysts, respectively. Also, the obtained Pt@Pd NCs showed improved catalytic activity and stability towards glycerol oxidation and hydrogen evolution reactions compared to the references.

Dentritic platinum-palladium/palladium core-shell nanocrystals/reduced graphene oxide: One-pot synthesis and excellent electrocatalytic performances.

Herein, we developed a facile one-pot co-reduction method to fabricate highly dentritic platinum-palladium/palladium core-shell nanocrystals on reduced graphene oxide (PtPd@Pd NCs/rGO), where poly-l-lysine (PLL) worked as the eco-friendly structure director and stabilizer. The nanocomposite was mainly characterized by microscopic analysis, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and thermogravimetric analysis (TGA), along with the discussion of the formation mechanism. The synthesized PtPd@Pd NCs/rGO have the enlarged electrochemically active surface area (ECSA) of 51.65 m2 g-1, showing 1.3 folds enhancement in the peak current density relative to commercial Pt/C (50 wt%) for glycerol oxidation reaction (GOR), coupled with the small Tafel slope of 28 mV dec-1 for hydrogen evolution reaction (HER).

Determination of morphine and codeine in urine using poly(dimethylsiloxane) microchip electrophoresis with electrochemical detection.

In this paper, a poly(dimethylsiloxane) (PDMS) microchip with electrochemical (EC) detection was developed for rapid separation and detection of morphine and codeine. It was found that morphine and codeine were well separated within 140 s in phosphate buffer solution (PBS) (pH 6.6, 40 mM)-beta-cyclodextrin (beta-CD) (20 mM)-acetonitrile (30%, v/v). The detection limit was 0.2 microM for morphine and 1 microM for codeine. The protocol was successfully applied to monitoring the amount of morphine and codeine in human urine. Compared with the conventional methods, the presented method had many advantages such as lower instrument cost, less reagent consumption and shorter analysis time.

One-pot controlled synthesis of AuPd@Pd core-shell nanocrystals with enhanced electrocatalytic performances for formic acid oxidation and glycerol oxidation.

In this work, AuPd@Pd core-shell nanocrystals (AuPd@Pd NCs) were fabricated by a one-pot co-reduction approach, where theophylline-7-acetic acid (TAA) acted asa new structure-directing agent. The crystal structure and composition were mainly characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), X-ray diffraction (XRD), together with X-ray photoelectron spectroscopy (XPS). The growth mechanism of AuPd@Pd NCs was investigated in detail. The obtained AuPd@Pd NCs exhibited superior catalytic characters for formic acid oxidation reaction (FAOR) and glycerol oxidation reaction (GOR) in contrast with commercial Pd black in alkaline media.

Separation of caffeine and theophylline in poly(dimethylsiloxane) microchannel electrophoresis with electrochemical detection.

A method for the rapid separation and sensitive determination of caffeine and theophylline was presented in poly(dimethylsiloxane) (PDMS) microchannel electrophoresis integrated with electrochemical detection. By using methanol as an additive, the peak shape and resolution were essentially improved. The analytes were well separated within only 40s in the running buffer of 5.0mM borate solution (pH 9.2) containing 10% (v/v) methanol. The linear ranges were from 6microM to 0.6mM and the detection limits were 4microM for caffeine and theophylline, respectively. The proposed method has been successfully applied to determine caffeine and theophylline in rat serum and urine.

Separation of three water-soluble vitamins by poly(dimethylsiloxane) microchannel electrophoresis with electrochemical detection.

A method for rapid separation and sensitive determination of three water-soluble vitamins, pyridoxine, ascorbic acid (VC), and p-aminobenzoic acid (PABA) has been developed by PDMS microchannel electrophoresis integrated with amperometric detection. After treatment of the microchip with oxygen plasma, the peak shapes of the three analytes were essentially improved. Pyridoxine, VC, and PABA were well separated within only 80 s in a running buffer of 20 mM borate solution (pH 8.5). Good linearity was obtained within the concentration range of 2-200 microM for the three water-soluble vitamins. The detection limits were 1.0 microM for pyridoxine and VC, and 1.5 microM for PABA. The proposed method has been successfully applied to real human urine sample, without solid phase extraction, with recoveries of 80-122% for the three water-soluble vitamins.