Dopant-Induced Interfacial Strain Enables Bifunctional Water Splitting in Ni-Doped SnS/MoS 2 Heterostructures: Data-Driven Insights

Abstract

ABSRTACTEfficient and earth-abundant photocatalysts for overall water splitting require simultaneous optimization of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities, a challenge rarely achieved within a single heterostructure. Here, single-atom 3d transition-metal doping transforms the SnS/MoS 2 heterostructure into an efficient bifunctional catalyst through interfacial strain and electronic-state engineering. First-principles calculations show that late transition-metal dopants electronically activate adjacent Sn and S atoms, dramatically accelerating HER kinetics. Ni doping drives the hydrogen adsorption free energy toward thermoneutrality (ΔG H* = -0.07 eV), markedly reduced from ~1.0 eV in pristine SnS/MoS 2 . To identify the governing structure-activity relationship, in silico-generated data are used to train an interpretable machine learning model, with mechanistic contributions quantified via Shapley Additive exPlanations (SHAP). The dopant-proximal Sn-S bond length emerges as the dominant descriptor controlling hydrogen adsorption energetics. The dopantinduced strain systematically tunes this bond, establishing interfacial bond-length engineering as a predictive design principle for HER optimization. Beyond HER, single Ni atoms stabilized on MoS 2 with threefold sulfur coordination act as highly active OER centers, delivering a low overpotential of 0.44 eV. The resulting Ni-doped SnS/MoS 2 thus overcomes the conventional HER-OER activity trade-off within a single earth-abundant platform. These findings provide a generalizable, descriptor-driven strategy for rational design of multifunctional water-splitting catalysts.