Co3S4/Fe3S4 heterostructured bifunctional catalyst evolved from CoFe LDH for effective overall water splitting in alkaline solution

In this study, unique Co3S4/Fe3S4 heterostructures (denoted as CoFe-HM-T) were synthesized from CoFe layered double hydroxides (LDHs) by a two-step hydrothermal process (hydrazine monohydrate and thiourea treatment). The effect of Co3S4/Fe3S4 heterostructures on the electrocatalytic water splitting was investigated in alkaline solution. The CoFe-HM-T electrode exhibited excellent oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) catalytic activity with overpotentials of 320 mV and 200 mV at the current density of 100 mA cm−2, respectively. CoFe-HM-T also possessed the smallest Tafel slope among the prepared samples, which was estimated to be 38.1 mV dec−1 and 144.9 mV dec−1 for OER and HER, respectively. Serving as bifunctional catalysts, the CoFe-HM-T electrode reached the state-of-art current density of 10 mA cm−2 at a cell voltage of 1.70 V with excellent stability. The enhanced electrocatalytic activity was ascribed to the interconnected structure facilitating the mass transport, the heterojunction accelerating the charge transfer, and the synergistic effect between them. This study offered a new strategy for in situ synthesizing the heterojunction electrocatalysts with unique interface by readily tuning the metal components in transition-metal LDHs.