Tubular g-C3N4 Isotype Heterojunction: Enhanced Visible-Light Photocatalytic Activity through Cooperative Manipulation of Oriented Electron and Hole Transfer

摘要

A tubular g-C3N4 isotype heterojunction (TCNH) photocatalyst was designed for cooperative manipulation of the oriented transfer of photogenerated electrons and holes to pursue high catalytic performance. The adduct of cyanuric acid and melamine (CA.M) is first hydrothermally treated to assemble into hexagonal prism crystals; then the hybrid precursors of urea and CA.M crystals are calcined to form tubular g-C3N4 isotype heterojunctions. Upon visible-light irradiation, the photogenerated electrons transfer from g-C3N4 (CA.M) to g-C3N4 (urea) driven by the conduction band offset of 0.05 eV, while the photogenerated holes transfer from g-C3N4 (urea) to g-C3N4 (CA.M) driven by the valence band offset of 0.18 eV, which renders oriented transfer of the charge carriers across the heterojunction interface. Meanwhile, the tubular structure of TCNH is favorable for oriented electron transfer along the longitudinal dimension, which greatly decreases the chance of charge carrier recombination. Consequently, TCNH exhibits a high hydrogen evolution rate of 63 mu mol h(-1) (0.04 g, lambda > 420 nm), which is nearly five times of the pristine g-C3N4 and higher than most of the existing g-C3N4 photocatalysts. This study demonstrates that isotype heterojunction structure and tubular structure can jointly manipulate the oriented transfer of electrons and holes, thus facilitating the visible-light photocatalysis.