Dopant-induced interfacial strain enables bifunctional water splitting in Ni-doped SnS/MoS2 heterostructures: data-driven insights

Abstract

Efficient 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/MoS₂ 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/MoS₂. To identify the governing structure–activity relationship, we use in silico-generated data 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 dopant-induced strain systematically tunes this bond, establishing interfacial bond-length engineering as a predictive design principle for HER optimization. The single Ni atoms stabilized on MoS₂ with threefold sulfur coordination further act as highly active OER centers, delivering significantly low overpotential. The resulting Ni-doped SnS/MoS₂ 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.