Sulphur Assisted Nitrogen‐Rich CNF for Improving Electronic Interactions in Co‐NiO Heterostructures Toward Accelerated Overall Water Splitting

Abstract Electrochemical water splitting is the eco‐friendly route to generate green hydrogen, which is recognized as sustainable energy for the future. However, the cost, operational efficiency, and long‐term durability of the electrochemical water splitting rely on the choice of the electrocatalysts. Hence, developing a superior design strategy is an important criterion to establish an efficient and sustainable water splitting system. Herein, a sulphur‐rich CoNiO heterostructure encapsulated on N‐rich carbon nanofibers (SCNO@N‐CNF) synthesized via a simple and efficient electrospinning technique is reported. The three‐way redox active centers, viz., the electron redistributed active Co^{δ ‐}NiO^{δ +} interfaces, S‐dopant sites with modified electronic density, and the porous N‐CNF matrix, makes the prepared electrocatalyst more efficient toward oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The SCNO@N‐CNF electrocatalyst exhibits a low OER and HER overpotentials (η_OER = 247 mV; η_HER = 169 mV) at a current density of 10 mA cm⁻². Moreover, SCNO@N‐CNF was analyzed as the bifunctional electrocatalyst in overall electrochemical water splitting, and it is found to deliver 10 mA cm⁻² at only 1.58 V. Thus, the design and engineering of multiple active elements in a single electrocatalyst is anticipated as an effective approach to establish an efficient and sustainable water splitting system.