Enhanced photocatalytic activity of all-solid-state g-C3N4/Au/P25 Z-scheme system for visible-light-driven H2 evolution

Abstract

We constructed an all-solid-state g-C3N4/Au/P25 Z-scheme system combining graphitic carbon nitride (g-C3N4) and P25 with Au nanoparticles, as an electron mediator, for hydrogen production under visible-light irradiation (λ > 400 nm). The g-C3N4/Au/P25 system was characterized by X-ray diffraction (XRD), transmission electronic microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–Vis diffuse reflection spectroscopy (UV–Vis DRS), photoluminescence (PL), time-resolved photoluminescence (TRPL), and electrochemical measurements. TEM and high-resolution transmission electron microscopy (HRTEM) clearly reveal the morphology and structure of g-C3N4/Au/P25, implying the existence of the all-solid-state Z-scheme system. The results of electrochemical impedance spectroscopy (EIS) and TRPL indicate that the Z-scheme system can effectively promote the electron transfer rate and the separation of photogenerated electron–hole pairs for the vectorial electron transfer of P25→Au→g-C3N4. The Z-scheme system can also extend the visible light absorption wavelength from 460 to 700 nm due to the surface plasmon resonance (SPR) effect of Au nanoparticles, which is confirmed by UV–Vis DRS and incident photo-to-current efficiency (IPCE) measurements. The synergistic effect of the all-solid-state g-C3N4/Au/P25 Z-scheme system and the Au-induced SPR results in a highly efficient photocatalytic performance with a turnover frequency (TOF) of 259 μmol h−1 g−1, which is 30 times higher than that of pristine g-C3N4.