Preparation and Voltammetric Application of a Zr(IV) Functionalized Spongolite for the Electrocatalytic Oxidation of Hydrazine

Abstract

This study demonstrates an additional exploration of the possibilities of modifying the surface of spongolite spicules, a biogenic silica, in order to prepare natural inorganic composites for application in catalytic oxidation processes. In this context, a novel hybrid material was synthesized from the inorganofunctionalization of a spongolite with zirconium(IV) (EZr). This material was then reacted with potassium hexacyanoferrate(III) and applied in a subsequent reaction with copper ions. The obtained material (EZrCuH) was characterized by scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), and cyclic voltammetry (CV). The CV of the graphite paste modified with EZrCuH exhibited two redox couples with midpoint potentials (Eθ′) equal to 0.36 and 0.74 V, attributed to the CuI/CuII and FeII(CN)6/FeIII(CN)6 processes (1.0 mol L−1, KCl pH 7.0, v = 20 mV s−1), respectively. The EZrCuH-modified graphite paste electrode presented electrocatalytic activity in the oxidation of different hydrazine concentrations and an analytical curve with a linear response of 8.0 × 10−7 to 4.0 × 10−5 mol L−1 (R2 = 0.999, relative standard deviation = ± 2% (n = 3)), and limit of detection of 8.33 × 10−7 mol L−1 and an amperometric sensitivity of 8.21 mA mol−1 L−1. Therefore, this material can be considered as a potential candidate for the manufacturing of electrochemical sensors intended for the easy and rapid detection of hydrazine substances.