Efficient oxidation of hydrazine over electrochemically activated glassy carbon electrode surface: Kinetics and sensing performance

Hazardous chemical hydrazine (HZ) can enter the body through the skin and harm the kidneys and liver. Consequently, it is imperative to accurately determine HZ concentrations in samples. One significant challenge in the direct and sensitive detection of analytes is the higher oxidation overpotential and inferior voltammetric response over the conventional bare electrode surface, attributed to the passivation of the electrode surface. To address this issue, we electrochemically activated (oxidized) a pristine glassy carbon electrode (GCE) in a mild acidic medium. The activated GCE demonstrated improved HZ oxidation efficiency. The activated GCE exhibited a distinct redox pair in 0.1 M H2SO4 because of the growth of CO groups onto the electrode surface during electrochemical oxidation. We characterized the GCE surface before and after the functionalization using electrochemical processes, Scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS). This activated electrode surface was utilized for electrochemical HZ oxidation in an alkaline medium, revealing enhanced electrochemical performance compared to the pristine GCE regarding HZ oxidation following conventional Butler-Volmer kinetics. Thorough electrochemical analyses and characterizations of the sensor were performed utilizing techniques such as Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS), Open Circuit Potential (OCP), Chronoamperometry (i-t curve), and Differential Pulse Voltammetry (DPV). The correlation between the current response and HZ concentration displayed an extensive linear dynamic range (LDR) spanning from 6 to 1000 μM, boasting a limit of detection (LOD) at 0.48 μM. The sensor's sensitivity was determined to be 3.1 μA μM−1 cm−2. The proposed activated GCE effectively reduces HZ oxidation overpotentials, thereby enhancing its potential application as an anode in direct hydrazine fuel cells.