Three-dimensional ordered macroporous materials with g-C3N4 and TiO2 as pore walls for efficient photocatalytic hydrogen evolution

Abstract

Three-dimensional ordered macroporous (3DOM) materials have been widely concerned due to the unique structure. Herein, pure TiO2, pristine g-C3N4, 3D-Ti (TiO2 with 3DOM structure) and 3D-xCN/Ti (x = 25 and 35 wt %) (3DOM materials with a certain ratio of TiO2 and g-C3N4 as the pore walls) were prepared. The morphologies of the samples were characterized by SEM, TEM and HRTEM, and the physical and chemical properties of the samples were explored by FT-IR, XPS, BET and UV–vis DRS. The 3D-25CN/Ti, with the structure of 3DOM and the couple of g-C3N4 and TiO2, extended the light spectral responsive range, and exhibited an excellent hydrogen evolution rate (14.1 mmol g−1 h-1), which was 28 times that of pure TiO2 (0.55 mmol g−1 h-1) under simulated sunlight. The high hydrogen evolution rate is attributed to the synergistic effect of the great separation and transfer capability of charge carriers and the larger specific area, which originate from the g-C3N4/TiO2 heterojunction and the 3DOM structure, respectively. The effective separation of the carriers was further confirmed through the photoluminescent spectroscopies and a series of photoelectrochemical experiments: Tafel, transient photocurrent response, electrochemical impedance. Finally, the mechanism of the photocatalytic hydrogen evolution was briefly discussed. These investigations reveal an important new strategy for improving the efficiency of photocatalytic hydrogen evolution.