Self-supported 3D coral-like copper/poly diphenylamine on nickel foam: multifunctional exploration of overall electrochemical water splitting, alcohol oxidation reaction and supercapacitor applications

Abstract

Across numerous industrial domains, including renewable energy systems, developing affordable, stable, long-lasting, and active electrocatalysts is imperative. Conventional catalysts have weak water splitting activity in alkaline medium because of their slow kinetics, high cost, and limited availability for large-scale production. A detailed investigation was conducted into the impact of copper (Cu) as a redox additive on the performance of a polydiphenylamine (PDPA) and three-dimensional copper/polydiphenylamine was electrodeposited potentiodynamically on nickel foam (NF) to achieve a binder-free electrocatalyst. This study describes the remarkable multifunctional capability of Cu/PDPA/NF for the hydrogen and oxygen evolution reaction, methanol & ethanol electro-oxidation and supercapacitor applications. The prepared electrode materials were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Raman spectroscopy, scanning electron microscopy & X-ray photoelectron spectroscopy (XPS) to analyse the structural and morphological characteristics. The excellent electrocatalytic activity of the Cu/PDPA/NF heterostructure for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) was observed with the overpotential and small Tafel slope values of 235.85 mV and 75 mV dec⁻¹ to reach 10 mA cm⁻² current density for the HER and 320 mV and 33.7 mV dec⁻¹ to reach 10 mA cm⁻² current density for the OER, respectively, in 1 M KOH electrolyte. In terms of their role in direct alcohol fuel cells (DAFCs) as anode catalysts, Cu/PDPA/NF exhibits the highest oxidation peak current density at 370 mA cm⁻², while for the ethanol oxidation reaction, the forward oxidation peak current density was 101.96 mA cm⁻². The synergistic effect of the polymer polydiphenylamine and copper also led to remarkable performance in terms of the areal capacitance of the material at 668 mF cm⁻² at a current density of 0.5 A cm⁻² with the capacitance retention of 81.3% after 5000 cycles at a current density of 10 A cm⁻², thus exhibiting energy storage capacity. The coral-like Cu/PDPA/NF designed in this study showcases improved electrochemical activity, which can lead to its usage in the broader applications of energy conversion and storage applications.