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A novel micro/nano-composite, based on cobalt(II) tetranitrophthalocyanine (CoTNPc) grown on poly(sodium-p-styrenesulfonate) modified graphene (PGr), as a non-noble-metal catalyst for the oxygen reduction reaction (ORR), is fabricated by an in situ solvothermal synthesis method. The CoTNPc/PGr is characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), respectively. The electrocatalytic activity of the CoTNPc/PGr composite toward the ORR is evaluated using cyclic voltammetry and linear sweep voltammetry methods. The CoTNPc/PGr composite exhibits an unexpected, surprisingly high ORR activity compared to CoTNPc or PGr. The onset potential for ORR on CoTNPc/PGr is found to be around -0.10 V vs. SCE in 0.1 M NaOH solution, which is 30 mV and 70 mV more positive than that on PGr and CoTNPc, respectively. The peak current density on CoTNPc/PGr is about 2 times than that on PGr and CoTNPc, respectively. Rotating disk electrode (RDE) measurements reveal that the ORR mechanism is nearly via a four-electron pathway on CoTNPc/PGr. The current density for ORR on CoTNPc/PGr still remains 69.9% of its initial value after chronoamperometric measurements for 24 h. Pt/C catalyst, on the other hand, only retains 13.3% of its initial current. The peak potential shifts slightly and current barely changes when 3 M methanol is added. The fabricated composite catalyst for ORR displays high activity, good stability and excellent tolerance to the crossover effect, which may be used as a promising Pt-free catalyst in alkaline direct methanol fuel cells (DMFCs).

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A dopamine (DA) sensor based on a methoxypolyethylene glycol (MPEG) polymer covalently modified glass carbon electrode (GCE) was fabricated by an electroadsorption method. The electrochemical behavior of the sensor towards the catalytic oxidation of DA in pH 5.0 phosphate buffer solution (PBS) was investigated by cyclic voltammetry. The modified electrode obviously enhanced the current response and decreased the overpotentials for the oxidation of DA. Using differential pulse voltammetry, the sensor gave a linear response to DA over the concentration range of 2.0-140 μM with a detection limit (S/N = 3) of 4.68 × 10(-8) M. It was found that MPEG can complex DA through hydrogen bonding interaction between ethylene oxide units of the polymer and the protonated dopamine in acidic PBS and preconcentrate it in the film, which improved the detection limit and sensitivity of DA. The DA sensor exhibits good sensitivity, selectivity and stability, and has been applied for the determination of DA in dopamine hydrochloride injection solution.