Atomic Pillar Effect in Pd_xNbS₂ To Boost Basal Plane Activity for Stable Hydrogen Evolution

Exploring novel electrocatalysts with prominent performance is highly demanded for electrochemical hydrogen evolution. As one family member of layered transition-metal dichalcogenides (TMDs), metallic niobium disulfide (NbS₂) with intrinsic basal plane activity might be a promising candidate once its electrical and structural characteristics are optimized. Here, we develop novel electrocatalysts by incorporating palladium (Pd) atoms into the van der Waals gaps of NbS₂ to form new compounds Pd_xNbS₂ (x = 0–0.23). On the basis of single crystal structure refinement and theoretical calculations, the Pd atoms act as atomic pillars to expand the interlayer spacing of NbS₂ and boost the basal plane activity with a drop of Gibbs free energy for hydrogen adsorption to 0.06 eV on neighboring S atoms, resulting in more protons to adsorb and react. In addition, pillared Pd stabilizes the crystal structure by connecting the NbS₂ interlayers with [PdS₆] octahedra. All these merits endow Pd_0.23NbS₂ with superior electrochemical activity and durability, achieving 10 mA cm^–2 at a low overpotential of 157 mV with a negligible change in 12 h. This unique atomic pillar effect for optimizing the electrocatalytic performance of Pd_xNbS₂ demonstrates a functional and powerful strategy to develop efficient TMD-based electrocatalysts.