title: 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-C3 N4 ), C+Fe-codoped g-C3 N4 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-C3 N4 for photodegradation of rhodamine B (RhB) increased 14 times, compared with pristine g-C3 N4 under visible-light absorption at λ>420 nm. The synergistic enhancement in C+Fe-codoped g-C3 N4 photocatalyst could be attributed to the following features: 1) C+Fe-codoping of g-C3 N4 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.
authors.affiliation: School for Radiological and Interdisciplinary Sciences, Soochow University, 215123, Suzhou (P.R. China); School of Materials Science and Engineering, Hefei University of Technology, Hefei 230031 (P.R. China).
authors.forename: Shouwei
authors.initials: S
authors.lastname: Zhang
authors.forename: Jiaxing
authors.initials: J
authors.lastname: Li
authors.forename: Meiyi
authors.initials: M
authors.lastname: Zeng
authors.forename: Jie
authors.initials: J
authors.lastname: Li
authors.forename: Jinzhang
authors.initials: J
authors.lastname: Xu
authors.forename: Xiangke
authors.initials: X
authors.lastname: Wang
keywords: band structure; carbon nitride; codoping; photocatalysis; reaction mechanisms