Sustainable engineering of wool keratin towards cobalt atoms fixation for enhanced electrocatalytic water splitting

Abstract

Developing sustainable bifunctional electrocatalysts based on non-noble metals for water splitting is crucial for modern society. Meanwhile, the utilization of biomaterials from waste streams in their fabrication enhances sustainability in the electrocatalytic sector. Herein, this novel approach has been demonstrated by selectively utilizing disulphide bonds, existed in natural wool keratin structure, to fabricate cobalt sulphide catalysts. The obtained Co9S8 nanoparticles, supported by nitrogen/phosphorus co-doped active carbons (Co9S8/N, P-ACs), exhibited a mesoporous system (SBET = 439.3 m2/g) and distinctive metal electronic environment. The as-prepared catalysts require a low overpotential of 90.7 mV and 245 mV to drive HER and OER at 10 mA cm−2 in the alkaline medium. The fabricated Co9S8/N,P-ACs Co9S8/N,P-ACs water electrolyzer possesses a low cell voltage (1.62 V at 10 mA cm−2) and a high stability with 9.8 % decay after 25 h of operation in the alkaline medium. Finally, density functional theory simulations confirm the octahedral sites in Co9S8 instead of CoO are the active sites, and an optimized d-band center is achieved by nitrogen, phosphorus-doped carbons.