Terminal p-π conjugation induced excited-state symmetry-breaking charge separation for porous carbon nitride based heterojunction

Highlights: • A novel ternary Ni₂P/ZnCdS/Porous g-C₃N₄ heterojunction nanophotocatalyst was constructed through hydrogen bonds. • Excited-state symmetry-breaking charge separation mechanism was unveiled by TD-DFT calculations. • The p-π conjugation NH_x and OH groups play dual essential roles in the improving of H₂ production activity. -- Abstract: To reach the purpose of high photocatalytic property, efficient charge separation is needed. Own to the low crystalline and two dimensional characters, it is rather harder to obtain the photoinduced charge transferring information for g-C₃N₄ than faceted crystal materials. Herein, images for distributions of photoinduced electrons and holes were utilized to analyze the excited-state characteristics and charge transfer directions. Both the theoretical calculation and experimental results reveal that the riched terminal NH_x p-π conjugation groups for defect porous carbon nitride (PCN) destroy the symmetry of intrinsic g-C₃N₄ (CN), which results in a spatial asymmetry distribution of photoinduced electrons and holes, and enhanced photocatalytic activity. To further improve PCN activity, a novel ternary Ni₂P/Zn_0.2Cd_0.8S/PCN photocatalyst was constructed and the H₂ evolution rate was 3.04 times of PCN. The enhanced H₂ generation performance is attributed to NH_x groups hydrogen bond induced well-connection in the ternary Ni₂P/Zn_0.2Cd_0.8S/PCN heterojunction photocatalysts.