title: Assembly of g-C3N4-based type II and Z-scheme heterojunction anodes with improved charge separation for photoelectrojunction water oxidation.
abstract: Graphitic carbon nitride (g-C3N4) has been widely studied as a metal-free photocatalyst, leading to some excellent results; however, the rapid recombination of photogenerated charge carriers substantially limits its performance. Here, we establish two types of g-C3N4-based heterojunction (type II and nonmediator assisted Z-scheme) photoanodes on a transparent conducting substrate via coupling with rod-like and nanoparticulate WO3, respectively. In these composites, g-C3N4film grown by electrophoretic deposition of exfoliated g-C3N4serves as the host or guest material. The optimized type II WO3/g-C3N4composite exhibits an enhanced photocurrent of 0.82 mA cm-2at 1.23 V vs. RHE and an incident photo-to-current conversion efficiency (IPCE) of 33% as compared with pure WO3nanorods (0.22 mA cm-2for photocurrent and 15% for IPCE). Relative to pure g-C3N4film (with a photocurrent of several microampere and an IPCE of 2%), a largely improved photocurrent of 0.22 mA cm-2and an IPCE of 20% were acquired for the Z-scheme g-C3N4/WO3composite. The enhancement can be attributed to accelerated charge separation in the heterointerface because of the suitably aligned band gap between WO3and g-C3N4, as confirmed by optical spectroscopy and ultraviolet photoelectron spectroscopy (UPS) analysis. The photocatalytic process and mechanism of the g-C3N4-based heterojunctions are proposed herein, which potentially explain the origin of the enhanced photoelectrochemical performance. This achievement and the fundamental information supplied here indicate the importance of rationally designing heterojunction photoelectrodes to improve the performance of semiconductors. This is particularly important for materials such as pure g-C3N4and WO3, as their photoactivities are strongly restricted by high recombination rates.
authors.affiliation: Key Lab of Bioelectrochemistry and Environmental Analysis of Gansu, College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou, Gansu 730070, People's Republic of China. luxq@nwnu.edu.cn.
authors.forename: Cai-He
authors.initials: CH
authors.lastname: Wang
authors.affiliation: Key Lab of Bioelectrochemistry and Environmental Analysis of Gansu, College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou, Gansu 730070, People's Republic of China. luxq@nwnu.edu.cn.
authors.forename: Dong-Dong
authors.identifier: http://orcid.org/0000-0002-8927-8601
authors.initials: DD
authors.lastname: Qin
authors.affiliation: Key Lab of Bioelectrochemistry and Environmental Analysis of Gansu, College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou, Gansu 730070, People's Republic of China. luxq@nwnu.edu.cn.
authors.forename: Duo-Liang
authors.initials: DL
authors.lastname: Shan
authors.affiliation: Department of Chemistry, San Diego State University, San Diego, CA 92182-1030, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Gu
authors.affiliation: Department of Chemistry and Environmental Science, New Jersey Institute of Technology, New Jersey 07102, USA.
authors.forename: Yong
authors.initials: Y
authors.lastname: Yan
authors.affiliation: Key Lab of Bioelectrochemistry and Environmental Analysis of Gansu, College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou, Gansu 730070, People's Republic of China. luxq@nwnu.edu.cn.
authors.forename: Jing
authors.initials: J
authors.lastname: Chen
authors.affiliation: Key Lab of Bioelectrochemistry and Environmental Analysis of Gansu, College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou, Gansu 730070, People's Republic of China. luxq@nwnu.edu.cn.
authors.forename: Qiu-Hong
authors.initials: QH
authors.lastname: Wang
authors.affiliation: Key Lab of Bioelectrochemistry and Environmental Analysis of Gansu, College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou, Gansu 730070, People's Republic of China. luxq@nwnu.edu.cn.
authors.forename: Cai-Hua
authors.initials: CH
authors.lastname: He
authors.affiliation: Key Lab of Bioelectrochemistry and Environmental Analysis of Gansu, College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou, Gansu 730070, People's Republic of China. luxq@nwnu.edu.cn.
authors.forename: Yang
authors.initials: Y
authors.lastname: Li
authors.affiliation: Key Lab of Bioelectrochemistry and Environmental Analysis of Gansu, College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou, Gansu 730070, People's Republic of China. luxq@nwnu.edu.cn.
authors.forename: Jing-Jing
authors.initials: JJ
authors.lastname: Quan
authors.affiliation: Key Lab of Bioelectrochemistry and Environmental Analysis of Gansu, College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou, Gansu 730070, People's Republic of China. luxq@nwnu.edu.cn.
authors.forename: Xiao-Quan
authors.identifier: http://orcid.org/0000-0002-3443-8612
authors.initials: XQ
authors.lastname: Lu