Freestanding eggshell membrane-based electrodes for high-performance supercapacitors and oxygen evolution reaction

Abstract

A type of freestanding, light-weight eggshell membrane-based electrode is demonstrated for supercapacitors and for oxygen evolution reaction (OER) catalysis. As a widely available daily waste, eggshell membranes have unique porous three-dimensional grid-like fibrous structures with relatively high surface area and abundant macropores, allowing for effective conjugation of carbon nanotubes and growth of NiCo₂O₄ nanowire arrays, an effective supercapacitor material and OER catalyst. The three-dimensional fibrous eggshell membrane frameworks with carbon nanotubes offer efficient pathways for charge transport, and the macropores between adjacent fibers are fully accessible for electrolytes and bubble evolution. As a supercapacitor, the eggshell membrane/carbon nanotube/NiCo₂O₄ electrode shows high specific capacitances at current densities from 1 to 20 A g⁻¹, with excellent capacitance retention (>90%) at 10 A g⁻¹ for over 10 000 cycles. When employed as an OER catalyst, this eggshell membrane-based electrode exhibits an OER onset potential of 1.53 V vs. the reversible hydrogen electrode (RHE), and a stable catalytic current density of 20 mA cm⁻² at 1.65 V vs. the RHE.