Atom-scale dispersed palladium in a conductive Pd0.1TaS2 lattice with a unique electronic structure for efficient hydrogen evolution

Abstract

Noble metal catalysts have extraordinary catalytic activity but suffer from high cost; therefore single atom catalysis attracts tremendous attention. Here, we propose atom-scale dispersed palladium (Pd) in a layered TaS₂ lattice to form new compounds of Pd_xTaS₂, whose crystal structure was resolved by powder X-ray diffraction. The electrical conductivity of metallic Pd_0.1TaS₂ (1.36 × 10⁴ S m⁻¹) is twice as large as that of TaS₂ (6.18 × 10³ S m⁻¹). This compound applied as a new electrocatalyst for the hydrogen evolution reaction (HER) exhibits excellent catalytic performance with an onset overpotential of 77 mV, superior to those of other catalysts such as TaS₂ (295 mV) and Pd-loaded TaS₂ (114 mV). Density functional theory calculations reveal that the interaction of Pd-4d and Ta-5d orbitals results in the upshift of the Fermi level (TaS₂versus Pd_0.1TaS₂) to decrease the barrier height for the HER. Furthermore, the hybridization of Pd-4d and S-3p orbitals builds up pathways along the c axis to improve the conductivity and promote HER performance. It is noted that the amount of Pd used in Pd_0.1TaS₂ is only 4 wt%, compared with 20 wt% in commercial Pd/C catalysts, which is beneficial for its practical application.