Phase Engineering Modulates the Electronic Structure of the IrO2/MoS2 Heterojunction for Efficient and Stable Water Splitting

The engineering of dual-functional catalytic systems capable of driving complete water dissociation in acidic environments represents a critical requirement for advancing proton exchange membrane electrolyzer technology, yet significant challenges remain. In this work, we investigate an IrO 2 /MoS 2 /CNT heterostructure catalyst demonstrating enhanced bifunctional performance for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) under acidic conditions. Strategic incorporation of IrO 2 into the MoS 2 /CNT heterojunction induces a partial phase transformation from 2H to the metastable 1T configuration in MoS 2, thereby modulating the electronic structure of IrO 2 and improving the catalytic performance for overall water splitting. The optimized IrO 2 /MoS 2 /CNT catalyst exhibited exceptional overpotentials of 9 mV (HER) and 182 mV (OER) at a current density of 10 mA cm –2 in acidic media. Full-cell evaluations further confirmed its practical potential, showing a 1.47 V operation voltage that outperforms standard Pt/C||IrO 2 counterparts by 120 mV. The experimental results revealed that the n–n heterojunction between IrO 2 /CNT and MoS 2 /CNT generates a built-in electric field, enhancing charge redistribution and electron transport. Moreover, density functional theory simulations further identify iridium centers as dominant catalytic loci, with a metastable 1T-MoS 2 phase mediating charge equilibration at atomic interfaces. This modification facilitates *OH adsorption and *OOH deprotonation and lowers the kinetic barrier during the water-splitting process.