Highly efficient metal-free ethylenediamine-functionalized fullerene (EDA@C60) electrocatalytic system for enhanced hydrogen generation from hydrazine hydrate

Abstract

A synthesized non-precious metal-free electrocatalyst is demonstrated using the hydrazine hydrate oxidation reaction as a model reaction of hydrogen production. The C₆₀ nanocomposite functionalized with ethylenediamine (EDA@C₆₀) was fabricated using a simple chemical approach. The EDA@C₆₀ composites were characterized using field emission scanning electron microscopy, energy dispersive analysis of X-rays, Fourier-transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, and electrochemical techniques. In this study, the nitrogen lone pairs from the ethylenediamine surface-functionalized on C₆₀ are responsible for the further enhancement of electrocatalytic activity towards the hydrazine oxidation reaction. Comparative electrochemical studies with acid-treated C₆₀, i.e., O–C₆₀, and the further-functionalized ethylenediamine catalysts (EDA@C₆₀) demonstrated high performance, which was ascribed to their inferior onset potential and better stability. The electrochemical measurements indicate that the EDA@C₆₀ composites demonstrate twice the current density (20 mA cm⁻²) and a better onset potential (0.2 V vs. SCE) than O–C₆₀ for hydrazine oxidation. The electrocatalytic hydrogen evolution reaction (HER) performance of the O–C₆₀ and EDA@C₆₀ electrocatalysts indicate onset potentials of 0.37 V vs. SCE and 0.20 V vs. SCE, respectively. The experimental and analytical studies found that the nanocomposites with ethylenediamine, i.e., EDA@C₆₀, not only extend the surface area compared to that of O–C₆₀, but also promote the self-decomposition of hydrazine molecules.