Selective in-situ derivatization of intrinsic nickel to nickel hexacyanoferrate on carbon nanotube and its application for electrochemical sensing of hydrazine

Abstract

Herein we report a simple and selective open-circuit potential-time (OCPT) based preparation of nickel hexacyanoferrate (NiHCF) on nickel and iron impurity containing carbon nanotube (CNT*, *=intrinsic metal impurity) modified glassy carbon electrode (GCE/CNT*NiHCF) using pH2 ferricyanide solution. Unlike potentiodyanamic cycling, OCPT allowed the selective preparation of NiHCF with a distinct redox features at an equilibrium potential=0.38V in pH7 phosphate buffer solution (PBS). Kinetic parameters such as transfer coefficient and rate constant of GCE/CNT*NiHCF were calculated from cyclic voltammetry (CV) studies of the redox peak. Characterization of CNT* and CNT*NiHCF by XRD, TEM, FTIR and Raman spectroscopy techniques revealed the presence of iron and nickel impurities in CNT* and confirmed the formation of CNT*NiHCF and CNT*Fe-NiHCF (Fe-NiHCF=FeHCF+NiHCF) by OCPT and potentiodynamic cycling, respectively. Furthermore, electrocatalytic activity of CNT*NiHCF modified electrode was explored with a model analyte, hydrazine (Hz) in pH7 PBS. Likewise, electron number involved during the rate determining step, complete electrocatalytic reaction and its heterogeneous rate constant values were calculated using CV technique. At optimal amperometric i-t conditions, GCE/CNT*NiHCF showed a linear calibration plot with a current linearity on a range of 20–200μM with current sensitivity and detection limit (signal-to-noise=3) values of 1217.39nAμM−1cm−2 and 0.8μM respectively. It also displayed zero interference from oxalic acid, uric acid, ascorbic acid, sulphate, nitrite, nitrite, magnesium and sodium displaying feasibility to Hz detection in polluted water bodies.