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Determining the Charge‐Transfer Direction in a p–n Heterojunction BiOCl/g‐C 3 N 4 Photocatalyst by Ultrafast Spectroscopy
Author(s) -
Chen Zongwei,
Zhang Qun,
Luo Yi
Publication year - 2017
Publication title -
chemphotochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.13
H-Index - 18
ISSN - 2367-0932
DOI - 10.1002/cptc.201700051
Subject(s) - photocatalysis , heterojunction , ultrafast laser spectroscopy , redox , picosecond , electron transfer , photodegradation , charge carrier , materials science , ultrashort pulse , absorption (acoustics) , spectroscopy , photochemistry , charge (physics) , chemistry , optoelectronics , physics , catalysis , optics , inorganic chemistry , organic chemistry , laser , composite material , quantum mechanics
Type‐II heterostructures composed of p‐type BiOCl and n‐type g‐C 3 N 4 have received much attention because of their high efficiencies of charge separation in photocatalysis. However, some ambiguity exists regarding the transfer direction of photogenerated charge carriers in the BiOCl(p)/g‐C 3 N 4 (n) system. Although it seems to have not posed an issue in terms of organic photodegradation applications, misinterpretation of the charge‐transfer direction and hence misjudgment of the redox sites in the hybrid system would be a serious problem for other photocatalytic reactions, especially for half reactions, in which the determination of the redox sites is crucial. To solve this problem, we carefully interrogated this topical heterojunction system formed between p‐type BiOCl and n‐type g‐C 3 N 4 by means of ultrafast transient absorption spectroscopy. Our experimental results reveal that the photogenerated electrons are transferred, on a time scale of a few picoseconds, from the conduction band of BiOCl to that of g‐C 3 N 4 and not in the opposite direction. This work enables us to eliminate the ambiguity in using two opposing mechanistic scenarios to describe the p–n heterojunction based photocatalysis mechanism, thereby providing instructive information for the rational design of photocatalytic nanosystems.