Simple vapor–solid-reaction route for porous Cu2O nanorods with good HER catalytic activity

Abstract

In this work, a simple vapor–solid reaction route was designed for the preparation of porous Cu₂O nanorods with good HER catalytic performance, employing Cu(OH)₂ nanorods as the precursor and ethylene glycol as the reductant. The reaction was carried out under an Ar atmosphere in the temperature range of 200–280 °C for 2 h. The final product was characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), (high-resolution) transmission electron microscopy (TEM/HRTEM), X-ray photoelectron spectroscopy (XPS), HAADF-STEM-EDS mapping and nitrogen adsorption–desorption isotherms. It was found that pure Cu₂O was always obtained in the temperature range of 200–280 °C and well retained the outline of the precursor. Nevertheless, electrochemical experiments showed that porous Cu₂O nanorods prepared at 200 °C (labeled as Cu₂O-200) exhibited much stronger HER catalytic activity than those obtained at higher temperatures, which were labeled as Cu₂O-220, Cu₂O-240, Cu₂O-260 and Cu₂O-280, respectively. In an alkaline solution of 1.0 M KOH, Cu₂O-200 presented a low overpotential of ∼184 mV, a small Tafel slope of 106 mV dec⁻¹, and a high durability over 20 h at a current density of 10 mA cm⁻². The above good performances were attributed to the high surface area and high-speed electronic transmission networks of Cu₂O-200, which provided fast transportation and short diffusion path for the electrolyte and evolved H₂ bubbles.