Evaluation of core-shell structured cobalt@platinum nanoparticles-decorated graphene for nitrite sensing

A new graphene composite was fabricated with cobalt (core) and platinum (shell) nanoparticles [Co@Pt/Gr] in two-steps preparation method. This prepared electrode combined the enhanced electrocatalytic activity of platinum, increased electrical conductivity of cobalt and high surface area of graphene. Compared with Pt/Gr, Co@Pt/Gr exhibited lowered onset potential value for nitrite oxidation in 0.1 M phosphate buffer solution with increased current density. Some related kinetic parameters for nitrite oxidation at Co@Pt/Gr electrode were calculated including Tafel slope, the exchange current density, the diffusion coefficient and the heterogeneous electron transfer rate constant values. Amperometry measurements demonstrated wide linear nitrite concentration ranges as 1 mu M-2 mM and 2-15 mM with remarkably increased sensitivity values of 45.96 and 97.71 mu A mM(-1) cm(-2), respectively. Co@Pt/Gr electrode showed a selective response for nitrite determination in presence of common interferents. The reproducibility and stability experiments also revealed good results suggesting Co@Pt/Gr electrode for effective and valuable detection of nitrite in medicine and environmental chemistry.