Doped nanocarbon materials (e.g., carbon nanotubes, graphene) are considered as effective electrocatalyst supports for fuel cells, and their electrochemical properties are closely related to the synthetic methods and the types of doping elements. In the current paper, we report a novel approach to synthesize sulfur-doped multi-walled carbon nanotubes (S-MWCNTs) as a highly efficient support material for Pt nanoparticle catalysts. The S-MWCNTs are obtained by annealing poly(3,4-ethylenedioxythiophene) (PEDOT) functionalized multi-walled carbon nanotubes at 800 °C. The prepared nanohybrids were physically characterized by Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). It has been found that the doping of sulfur into MWCNTs could significantly improve the dispersion of supported Pt nanoparticles of 2.37 nm in size and increase the electrochemically active surface area (ECSA, 161.4 m2 g−1). The doped sulfur atoms not only provide uniformly dispersed anchoring sites for the deposition of Pt nanoparticles on the surface of MWCNTs but also enhance the electron transfer interaction between Pt nanoparticles and the S-MWCNT support. The electrochemical properties of the catalysts were evaluated by using cyclic voltammetry (CV) and chronoamperometry (CA) techniques. The results demonstrate that the as-prepared Pt/S-MWCNTs exhibit much higher electrocatalytic activity, long-term durability and CO-tolerance ability for the methanol oxidation reaction (MOR) compared to the undoped MWCNT supported Pt and commercial Pt/C catalysts.

•A core-shell structured Ru@Pd/MWCNT nanocatalyst is reported.•Ru@Pd nanoparticles with smaller size are evenly deposited on the MWCNTs.•There is strong electron interaction between Pd and Ru on the catalytic surface.•The Ru@Pd/MWCNT exhibits much higher electrocatalytic performance for EOR and FAO.Herein, we report the facile synthesis of core-shell structured Ru@Pd/multi-walled carbon nanotube (MWCNT) catalyst via a two-step chemical reduction process without any surfactant and its electro-catalytic performance for ethanol and formic acid oxidation. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results revealed that the Ru@Pd nanoparticles are quite uniformly distributed on the surface of MWCNT with an average particle size of 2.3 nm. X-ray photoelectron spectroscopy (XPS) analysis showed the strong charge transfer interaction between Pd and Ru atoms on catalytic surface. The electrochemical studies demonstrated that the Ru@Pd/MWCNT catalyst exhibits higher peak current density and significantly enhanced long-term stability toward the anodic oxidation of ethanol in alkaline medium. Its electro-catalytic activity for ethanol oxidation is 1.8 and 2.7 times higher than that of Pd/MWCNT and commercial Pd/C catalysts, respectively, indicating the high utilization of Pd in as-prepared Ru@Pd/MWCNT catalyst. Moreover, the Ru@Pd/MWCNT also presents the enhanced electro-catalytic activity for formic acid oxidation (FAO) in acidic medium. This study opens up a new way for the fabrication of Pd-based electrocatalysts with high performance and low cost.A core-shell structured Ru@Pd/MWCNT catalyst via a simple two-step chemical reduction process without any surfactant is reported. The Ru@Pd/MWCNT exhibits much higher catalytic activity and stability for the EOR and FAOR than those of the Pd/MWCNT and commercial Pd/C catalysts.Download full-size image

•A strategy in DESs for PtCo/MWCNT nanocatalysts is reported.•The alloyed PtCo nanoparticles with small sizes are deposited on the MWCNT surface.•There is strong electron interaction between Pt and Co on the catalytic surface.•The PtCo/MWCNTs exhibit much higher electrocatalytic performance for MOR.We herein report a novel strategy for multi-walled carbon nanotube (MWCNT)-supported PtCo nanocatalysts, which are synthesized in deep eutectic solvents (DESs) by a chemical reduction route. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) results indicate that the alloyed PtCo nanoparticles of ca. 2.4 nm are deposited on the surface of MWCNTs with less aggregation in larger clusters. X-ray photoelectron spectroscopy (XPS) measurements reveal the strong charge transfer interaction between Pt and Co atoms in the PtCo/MWCNT catalyst. The electrochemical tests illustrate that the PtCo/MWCNT exhibits much higher electrocatalytic activity, stability and CO tolerance ability than the Pt/MWCNT catalyst for the methanol oxidation reaction (MOR). This study implies that the method based on DESs will be potential in design and fabrication of the highly efficient electrocatalysts for DMFCs applications.

•A new Pt-based catalyst using PIn-functionalized MWCNTs as support is reported.•There is strong electron interaction between Pt nanoparticles and PIn-MWCNTs.•Pt nanoparticles with small sizes are evenly deposited on the PIn-MWCNT surface.•The Pt/PIn-MWCNTs exhibit much higher electrocatalytic performance for MOR.Herein, we report a novel electrocatalyst consisting of Pt nanoparticles supported on a polyindole (PIn)-functionalized multi-walled carbon nanotube (MWCNT) composite (Pt/PIn-MWCNT) for use in the methanol oxidation reaction (MOR). The PIn-MWCNT support is synthesized via in situ chemical polymerization of indole on the MWCNT surface. The transmission electron microscopy (TEM) images indicated that the Pt nanoparticles were approximately 3.0 nm in size and were uniformly deposited on the surface of PIn-MWCNTs with no aggregation into larger clusters. X-ray photoelectron spectroscopy (XPS) measurements confirm the strong electron interaction between the Pt nanoparticles and the PIn-MWCNT support as well as the formation of the Pt–N bond. The electrochemical tests demonstrate that the Pt/PIn-MWCNT composite exhibits much higher electrocatalytic activity, durability and CO tolerance than the Pt/MWCNT and commercial Pt/C catalysts toward MOR. The results indicate that the as-prepared Pt/PIn-MWCNTs are promising for use as an anode electrocatalyst in direct methanol fuel cells (DMFCs).

We report on a novel electrochemical dopamine (DA) sensor based on a glassy carbon electrode (GCE) modified with a hybrid material composed of Cu(I) oxide hollow microspheres and carbon black. The hybrid material was synthesized in a mixed solvent composed of water and the deep eutectic solvent choline chloride/urea, and by in-situ reduction of Cu(II) by ascorbic acid. The surface morphology and structure of the materials were characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. Cyclic voltammetry and chronoamperometry were used to evaluate the electrocatalytic properties of the modified GCE toward DA oxidation in phosphate buffer solution of pH 5.7. The sensor displays a higher electrocatalytic activity toward DA oxidation compared to other modified electrodes. At a working potential of 0.25 V (vs. SCE), the sensor exhibits a rapid response (<3 s) and a wide linear range from 9.9 × 10−8 to 7.08 × 10−4 mol L−1. The detection limit is as low as 3.96 × 10−8 mol L−1 (S/N = 3). In addition to its high sensitivity, the sensor displays good reproducibility, long-term stability and fair selectivity.

•A new Pd-based catalyst using TSCuPc functionalized MWCNTs as support is reported.•Pd nanoparticles are uniformly dispersed on the functionalized MWCNTs surface.•The Pd/TSCuPc-MWCNTs shows excellent catalytic performance for formic acid oxidation.The hydrothermal synthesis of a novel Pd electrocatalyst using copper phthalocyanine-3,4′,4″,4′″-tetrasulfonic acid tetrasodium salt (TSCuPc) functionalized multi-walled carbon nanotubes (MWCNTs) composite as catalyst support for Pd nanoparticles is reported. The prepared nanocomposites were characterized by UV–vis absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electrochemical tests. It is found that Pd nanoparticles are uniformly deposited on the surface of TSCuPc-MWCNTs, and their dispersion and electrochemical active surface area (ECSA) are significantly improved. Studies of cyclic voltammetry and chronoamperometry demonstrate that the Pd/TSCuPc-MWCNTs exhibits much higher electrocatalytic activity and stability than the Pd/AO-MWCNTs catalyst for formic acid oxidation. This study implies that the as-prepared Pd/TSCuPc-MWCNTs will be a promising candidate as an anode electrocatalyst in direct formic acid fuel cell (DFAFC).

•A new Pt nanoparticles electrocatalyst using copper phthalocyanine (TSCuPc) functionalized graphene as support is reported.•Pt nanoparticles with high electrochemical active surface area are uniformly deposited on the functionalized graphene surface.•The Pt/TSCuPc–graphene catalyst exhibits much higher electrocatalytic activity and stability for methanol oxidation.We herein report a facile and effective ultrasonication method to non-covalently functionalize graphene with copper phthalocyanine-3,4′,4″,4‴-tetrasulfonic acid tetrasodium salt (TSCuPc) as a promising catalyst support for Pt nanoparticles. With the assistance of TSCuPc, Pt nanoparticles are homogeneously deposited on the surface of graphene, and their dispersivity and electrochemical active surface area (ECSA) are obviously enhanced. Studies of cyclic voltammetry and chronoamperometry demonstrate that the as-prepared Pt/TSCuPc–graphene catalyst exhibits much higher electrocatalytic activity and stability than the Pt/graphene and commercial Pt/C catalysts for methanol oxidation. It is concluded that the strategy of TSCuPc-functionalized graphene with Pt catalysts will be potential in design and synthesis of the highly efficient electrocatalysts for DMFCs applications.

•A new Pt-based catalyst using the MnOx–PEDOT–MWCNTs composite as support is reported.•Highly dispersed Pt nanoparticles are uniformly deposited on the MnOx–PEDOT–MWCNTs.•The catalyst shows high catalytic performance for methanol oxidation reaction (MOR).We herein report a novel Pt-based electrocatalyst for direct methanol fuel cells (DMFCs) using multi-walled carbon nanotubes (MWCNTs) supported manganese oxide and poly(3,4-ethylenedioxythiophene) (PEDOT) nanocomposite (MnOx–PEDOT–MWCNTs) as catalyst support for Pt nanoparticles. The prepared nanocomposites are characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electrochemical tests. The results demonstrate that Pt nanoparticles are uniformly deposited on the surface of MnOx–PEDOT–MWCNTs, and their dispersion and electrochemical active surface area (ECSA) are obviously improved. The methanol electrooxidation activity and stability of the Pt/MnOx–PEDOT–MWCNTs are significantly enhanced as compared with the Pt/PEDOT–MWCNTs and Pt/MWCNTs catalysts. This study implies that the as-prepared Pt/MnOx–PEDOT–MWCNTs will be a promising candidate as an anode electrocatalyst in DMFCs.

•A novel electrochemical glucose biosensor based on the graphene multilayer film has been developed.•Graphene was noncovalently functionalized with two kinds of copper phthalocyanines.•The multilayer film was prepared through layer-by-layer assembly technique.•The biosensor exhibited good analytical performance for glucose detection.A negatively charged glassy carbon electrode (GCE) was formed through the electrochemical modification of sulfanilic acid (ABS). Subsequently, graphene composites functionalized with copper phthalocyanine-3,4′,4″,4‴-tetrasulfonic acid tetrasodium salt (TSCuPc) or alcian blue pyridine variant (AB) were assembled layer-by-layer (LbL) via alternate electrostatic adsorption onto the ABS/GCE surface to obtain a uniform and stable graphene multilayer film modified electrode. With glucose oxidase (GOD) as an enzyme model, a novel GOD/Nafion/(LbL)3.5/ABS/GCE electrochemical biosensor has been developed. SEM and Raman spectra were utilized to characterize the functionalized graphene nanocomposites and modified electrodes. The electrochemical performance of the biosensor was investigated by cyclic voltammetry. The results demonstrated that the graphene multilayer film significantly enhanced the electrocatalytic activity of the modified electrode toward O2 reduction. Based on the O2 consumption during the oxidation process of glucose, the as-prepared biosensor exhibited a low detection limit of 0.05 mmol L−1, excellent reproducibility, stability, sensitivity and selectivity, and its response was linear up to 8 mmol L−1 glucose concentration. Accordingly, the multilayer film consisting of copper phthalocyanine functionalized graphene nanocomposites offers a novel and effective platform for the electrochemical biosensing applications.

•A new Pt-based catalyst using TSNiPc functionalized graphene as support is reported.•Pt nanoparticles are uniformly dispersed on the functionalized graphene surface.•The Pt/TSNiPc–graphene shows excellent catalytic performance for methanol oxidation.A novel electrocatalyst using nickel (II) phthalocyanine-tetrasulfonic acid tetrasodium salt (TSNiPc) functionalized graphene (TSNiPc–graphene) composite as catalyst support for Pt nanoparticles is reported. The surface morphology, composition and structure of the prepared nanocomposites as well as their electrocatalytic properties toward methanol oxidation are characterized by UV–vis absorption spectroscopy, Raman spectroscopy, thermogravimetric analysis (TGA), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical tests. Pt nanoparticles are found uniformly dispersed on the surface of TSNiPc–graphene composite, with the small particle size of about 3.1 nm. Studies of cyclic voltammetry and chronoamperometry demonstrate that the Pt/TSNiPc–graphene exhibits much higher electrocatalytic activity and stability than the Pt/graphene catalyst for methanol oxidation.

The electrochemically shape-controlled synthesis in deep eutectic solvents (DESs) has been applied to produce the electrocatalyst of Pt nanoflowers. The uniform Pt nanoflowers with sharp single crystal petals and high density of atomic steps were characterized by SEM, TEM, XRD, XPS and electrochemical tests. The results illustrated that the as-prepared Pt nanoflowers exhibit higher electrocatalytic activity and stability than commercial Pt black catalyst toward ethanol electrooxidation. The growth of Pt nanoflowers in DESs by the simple electrochemical route is straightforward and controllable in terms of nanoflowers’ shape and size, which can be applied in shape-controlled synthesis of other noble metal nanoparticles with high catalytic activity.Highlights► The electrochemically shape-controlled synthesis in deep eutectic solvents (DESs) has been applied to produce the uniform Pt nanoflowers with sharp single crystal petals and high density of atomic steps. ► The as-prepared Pt nanoflowers exhibit higher electrocatalytic activity and stability than commercial Pt black catalyst toward ethanol electrooxidation. ► The growth of Pt nanoflowers in DESs by the simple electrochemical route is straightforward and controllable in terms of nanoflowers’ shape and size.

In the present paper, we have developed for the first time the electrochemically shape-controlled synthesis in deep eutectic solvents (DESs) for the preparation of Pt nanocrystals enclosed by high-index facets. Monodispersed concave tetrahexahedral Pt nanocrystals (THH Pt NCs) have been prepared through this new route. The concave THH Pt NCs were characterized by SEM, TEM, and AFM. The as-prepared concave Pt NCs are bounded with {910} and vicinal high-index facets, which exhibit superior catalytic activity and stability to those of the commercial Pt black catalyst for ethanol electrooxidation. We have demonstrated also that the electrochemically shape-controlled synthesis in DESs proves advantageous in controlling the size and shape of Pt NCs without the addition of seeds, surfactants, or other chemicals and could be applied in the synthesis of other noble metal NCs with high surface energy and high catalytic activity.

The dissociative adsorption of ethylene glycol (EG) on stepped surfaces of Pt single crystal (Pt(s) − [n(100) × (111)]) was investigated. Different surface structures of these platinum single crystal electrodes were obtained by various treatment conditions. The results illustrated that the electrocatalytic activity of Pt single crystal electrodes towards EG dissociative adsorption is increased with the increase of (100) terrace length on the surfaces. It has been found that the different pretreatment hardly influences the reactivity of stepped Pt(s) − [n(100) × (111)] surfaces towards EG dissociative adsorption. The results indicated that all studied surfaces are more active in perchloric acid than in sulfuric acid, and this effect is decreased with the increase of (100) terrace length on the surfaces, demonstrating the strong adsorption of (bi)sulfate anions on (111) sites and their weak adsorption on (100) sites. This study has gained knowledge on the interaction between EG and Pt single crystal electrodes, and thrown a new insight into understanding the fundamental of electrocatalysis and surface processes of EG dissociative adsorption.► The electrocatalytic activity of Pt single crystal electrodes towards EG dissociative adsorption is increased with the increase of (100) terrace length on the stepped surfaces. ► Different pretreatments could hardly influence the reactivity of stepped Pt(s)–[n(100)×(111)] surfaces. ► The effect of specific adsorption of (bi)sulfate anions on EG dissociative adsorption is decreased with the increase of (100) terrace length on the surfaces, demonstrating the strong adsorption of (bi)sulfate anions on (111) sites and their weak adsorption on (100) sites.