Atomic Pillar Effect in PdxNbS2 to Boost Basal Plane Activity for Stable Hydrogen Evolution

Abstract

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 PdxNbS2 (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 Pd0.23NbS2 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 PdxNbS2 demonstrates a functional and powerful strategy to develop efficient TMD-based electrocatalysts.