Bandgap Engineering and Mechanism Study of Nonmetal and Metal Ion Codoped Carbon Nitride: C+Fe as an Example

Abstract Bandgap narrowing and a more positive valence band (VB) potential are generally considered to be effective methods for improving visible‐light‐driven photocatalysts because of the significant enhancement of visible‐light absorption and oxidation ability. Herein, an approach is reported for the synthesis of a novel visible‐light‐driven high performance polymer photocatalyst based on band structure control and nonmetal and metal ion codoping, that is, C and Fe‐codoped as a model, by a simple thermal conversion method. The results indicate that compared to pristine graphitic carbon nitride (g‐C 3 N 4 ), C+Fe‐codoped g‐C 3 N 4 shows a narrower bandgap and remarkable positively shifted VB; as a result the light‐absorption range was expanded and the oxidation capability was increased. Experimental results show that the catalytic efficiency of C+Fe‐codoped g‐C 3 N 4 for photodegradation of rhodamine B (RhB) increased 14 times, compared with pristine g‐C 3 N 4 under visible‐light absorption at λ >420 nm. The synergistic enhancement in C+Fe‐codoped g‐C 3 N 4 photocatalyst could be attributed to the following features: 1) C+Fe‐codoping of g‐C 3 N 4 tuned the bandgap and improved visible‐light absorption; 2) the porous lamellar structure and decreased particle size could provide a high surface area and greatly improve photogenerated charge separation and electron transfer; and 3) both increased electrical conductivity and a more positive VB ensured the superior electron‐transport property and high oxidation capability. The results imply that a high‐performance photocatalyst can be obtained by combining bandgap control and doping modification; this may provide a basic concept for the rational design of high performance polymer photocatalysts with reasonable electronic structures for unique photochemical reaction.