Eggshell membrane-derived electrocatalysts for water electrolysis

Green H₂ (GH2) holds significant promise as a renewable energy resource, particularly in addressing the escalating energy demands sustainably. The imperative for economically viable GH2 technologies, primarily via water electrolysis, has spurred extensive research into suitable electrocatalytic materials. Eggshell membrane (ESM) is typically considered a biowaste material obtained from eggs, which are among the most widely consumed foods both domestically and industrially. Many countries legally require the effective treatment of ESM before disposal to prevent environmental contamination. Therefore, we propose upcycling ESM as an electrocatalytic support, forming transition metal-based active sites through chemical and thermal treatment, followed by doping highly reactive Fe sites electrochemically. ESM's nanofibrous morphology and porous structure confer catalytic advantages. X-ray photoelectron spectroscopy analysis reveals that certain chemical functional groups in the ESM are involved in the spontaneous electrochemical charge transfer and the adsorption of metal ions, contributing to the formation of metal nanoparticles. Furthermore, various anionic chemical elements such as P, O, N, and S, which originate from intrinsic ESM, can participate in electrocatalysis. The Fe sites electrochemically induced on the Ni and Co nanoparticle surfaces in the ESMs demonstrate excellent electrocatalytic activity and durability toward the oxygen and hydrogen evolution reactions, respectively. This study provides a strategy to utilize ESM as an electrocatalytic material for the development of commercially viable electrocatalysts to produce GH2 by transforming biowaste into value-added materials. Moreover, it promotes the investigation of the (electro)chemical functionalities of biomaterials and the correlation between their functions and electrocatalytic activities.