Hybridization of iron phthalocyanine and MoS2 for high-efficiency and durable oxygen reduction reaction

Abstract

Hybrid catalysts based on iron phthalocyanine (FePc) have raised much attention due to their promising applications in electrocatalytic oxygen reduction reaction (ORR). Various hybridization strategies have been developed for improving their activity and durability. However, the influence of different hybridization strategies on their catalytic performance remains unclear. In this study, FePc was effectively distributed on molybdenum disulfide (MoS2) forming FePc-based hybrid catalysts, namely FePc-MoS2, FePc*-MoS2, and FePc-Py-MoS2, respectively, to disclose the related influence. Through direct hybridization, the stacked and highly dispersed FePc on MoS2 resulted in FePc-MoS2, and FePc*-MoS2, respectively, in which the substrate and FePc are mainly bound through van der Waals interactions. Through covalent hybridization strategy using pyridyl (Py) as a linker, FePc-Py-MoS2 hybrid catalyst was prepared. Experimental and theoretical results disclosed that the linker hybridization of FePc and MoS2 facilitated the exposure of Fe-N4 sites, maintained the intrinsic activity of FePc by forming a more dispersed phase and increased the durability via Fe-N bonding, rendering the FePc-Py-MoS2 an excellent ORR hybrid catalyst. Compared with van der Waals hybridized FePc-MoS2 and FePc*-MoS2 in alkaline media, the linker hybridized FePc-Py-MoS2 showed an obviously enhanced ORR activity with a half-wave potential (E1/2) of 0.88 V vs RHE and an ultralow Tafel slope of 26 mV dec-1. Besides, the FePc-Py-MoS2 exhibited a negligible decay of E1/2 after 50,000 CV cycles for ORR, showing its superior durability. This work gives us more insight into the influence of different hybrid strategies on FePc catalysts and provides further guidance for the development of highly efficient and durable ORR catalysts.