Modulating vacancies of graphene supported FeNi₂S₄ electrocatalysts by radio-frequency plasma for overall water splitting

Abstract

Electrolysis of water for producing hydrogen is an effective and sustainable technique to meet the continuously increasing energy demand. Nevertheless, its advancement is impeded by the inadequate catalytic efficacy for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Vacancy defect engineering is a rational approach to simultaneously enhance the catalytic performance for both the half-reactions. However, controlling the vacancy defects is quite challenging. Here, we have employed a radio-frequency Ar plasma-assisted treatment strategy to prepare highly efficient graphene-supported FeNi2S4 bifunctional catalysts with abundant vacancies. The plasma treatment induces the formation of vacancy structures in the catalyst, modifying the free energy of reaction intermediates, surface morphology, and electronic structure as well as reducing the reaction barriers, thereby enhancing the catalytic performance. The optimized graphene-supported FeNi2S4 catalyst possesses abundant sulfur vacancies, demonstrating excellent electrocatalytic performance. At 50 mA cm-2, the overpotentials for OER and HER are 240 and 256 mV, respectively, indicating exceptional stability. Overall, this work offers valuable insights into the development of cost-effective and high-performance electrocatalysts for water electrolysis.