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 IrO2/MoS2/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 IrO2 into the MoS2/CNT heterojunction induces a partial phase transformation from 2H to the metastable 1T configuration in MoS2, thereby modulating the electronic structure of IrO2 and improving the catalytic performance for overall water splitting. The optimized IrO2/MoS2/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||IrO2 counterparts by 120 mV. The experimental results revealed that the n–n heterojunction between IrO2/CNT and MoS2/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-MoS2 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.