Co, N co-doping controlled preparation of FeS/FeS2 heterojunction for efficient overall water splitting

The low electrical conductivity and catalytic activity of transition metal sulfides have been identified as the primary factors limiting their application in the field of electrocatalytic water splitting. In this study, FeS 2 and Co-FeS x were initially synthesized through a hydrothermal method, followed by further annealing in an NH 3 atmosphere to obtain Co,N-FeS x . The introduction of Co led to adjustments in the electronic structure, resulting in the formation of FeS 2 /FeS (FeS x ) heterojunctions that facilitated accelerated charge transfer. Simultaneously, Co element doping increased the electrochemical active surface area, providing more active sites for the reactions. N element doping, on the other hand, introduced sulfur vacancies, thereby enhancing electrical conductivity and improving charge transfer efficiency. As a result, Co,N-FeS x exhibited significantly higher activities for the oxygen evolution reaction (OER) and overall water splitting compared to FeS 2 , with overpotentials of 290 mV and 330 mV, respectively, at a current density of 10 mA cm −2 . Furthermore, the catalyst demonstrated excellent stability. The designed structure of the catalyst provides theoretical support for the study of Fe-based catalysts in OER and overall water splitting.