Zhixiang Zheng

Simultaneous electrochemical determination of uric acid, xanthine and hypoxanthine based on poly(l-arginine)/graphene composite film modified electrode

Poly(l-arginine)/graphene composite film modified electrode was successfully prepared via a facile one-step electrochemical method and used for simultaneous determination of uric acid (UA), xanthine (XA) and hypoxanthine (HX). The electrochemical behaviors of UA, XA and HX at the modified electrode were studied by cyclic voltammetry and differential pulse voltammetry (DPV), and showed that the modified electrode exhibited excellent electrocatalytic activity toward the oxidation of the three compounds. The calibration curves for UA, XA and HX were obtained over the range of 0.10-10.0, 0.10-10.0 and 0.20-20.0 μM by DPV, respectively and the detection limits for UA, XA and HX were 0.05, 0.05 and 0.10 μM (S/N=3), respectively. With good selectivity and high sensitivity, the modified electrode has been applied to simultaneous determination of UA, XA and HX in human urine with satisfactory result.

High electrocatalytic activity of non-noble Ni-Co/graphene catalyst for direct ethanol fuel cells

The electrocatalytic oxidation of ethanol is studied on the non-noble catalysts Ni-Co/graphene and Ni/graphene supported on glass carbon electrode (GCE) in alkaline medium. The synthesized materials are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and scanning transmission electron microscopy. The elements of Ni-Co/graphene and Ni/graphene catalysts are characterized using energy-dispersive X-ray spectroscopy. The electrocatalytic properties of Ni-Co/graphene and Ni/graphene for ethanol oxidation are investigated by cyclic voltammetry, chronoamperometry, and Tafel plot. Compared with Ni/graphene catalyst, Ni-Co/graphene has the higher electroactivity and better stability for ethanol oxidation. The rate constant (ks) and charge-transfer coefficient (α) are calculated for the electron exchange reaction of the modified GCE. The results indicate that Co addition could promote the oxidation reaction at the Ni/graphene catalyst. Our study demonstrates that the low-cost electrocatalyst Ni-Co/graphene has a great potential for real direct ethanol fuel cells’ application.