Synthesis of ultrathin PdSe2 flakes for hydrogen evolution reaction

Highlights: • Ultrathin 2D PdSe₂ flakes are achieved through an APCVD method. • PdSe₂ is investigated by STEM, Raman spectroscopy, and SHG techniques. • The PdSe₂ flakes display outstanding electrocatalytic performance for HER. Two-dimensional (2D) palladium diselenide (PdSe₂) has demonstrated great promise in electronics and optoelectronics due to its remarkable air stability, appealing carrier mobility, and controllable bandgap. However, realizing the synthesis of 2D PdSe₂ remains still a daunting challenge. Herein, high-quality, ultrathin (∼2.2 nm) 2D PdSe₂ flakes are achieved on mica substrates through a NaCl-assisted ambient-pressure chemical vapor deposition method. We systematically probe the crystal quality and optical characteristics in PdSe₂ using scanning transmission electron microscopy, angle-resolved polarized Raman spectroscopy, and second harmonic generation characterizations. Impressively, the transferred PdSe₂ flakes on Au foil, featuring lower overpotential of ∼ 150 mV at 10 mA/cm², lower Tafel slope of ∼ 70 mV/dec, higher exchange current density of ∼ 85 μA/cm², and superior stability, display outstanding electrocatalytic performance for hydrogen evolution reaction (HER). This work shows a promising prospect of PdSe₂ in electrocatalysis for HER.