Synthesis of ultrathin PdSe2 flakes for hydrogen evolution reaction

Two-dimensional (2D) palladium diselenide (PdSe) 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 PdSe remains still a daunting challenge. Herein, high-quality, ultrathin (∼2.2 nm) 2D PdSe 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 PdSe using scanning transmission electron microscopy, angle-resolved polarized Raman spectroscopy, and second harmonic generation characterizations. Impressively, the transferred PdSe flakes on Au foil, featuring lower overpotential of ∼ 150 mV at 10 mA/cm, lower Tafel slope of ∼ 70 mV/dec, higher exchange current density of ∼ 85 μA/cm, and superior stability, display outstanding electrocatalytic performance for hydrogen evolution reaction (HER). This work shows a promising prospect of PdSe in electrocatalysis for HER.