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One-Pot Ionothermal Synthesized Carbon Nitride Heterojunction Nanorods for Simultaneous Photocatalytic Reduction and Oxidation Reactions: Synergistic Effect and Mechanism Insight

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journal contribution
posted on 04.02.2019, 00:00 by Ailing Jin, Xin Liu, Mengru Li, Yushuai Jia, Changfeng Chen, Xiangshu Chen
Band structure and crystallinity engineering of polymeric semiconductors provides effective strategies for photocatalytic activity enhancement. Here, a facile one-step ionothermal method was developed to achieve the in situ growth of carbon nitride (CN) isotype heterojunctions (ms-CN-x) using KCl/LiCl eutectic salts as the high-temperature solvent and urea as the starting material, which are demonstrated to be efficient photocatalysts for removal of toxic heavy metal and organic pollutant in a single or coexisting system. The as-obtained ms-CN-x composite material appears as well-ordered nanorod structure with high crystallinity and consists of phases of both heptazine-based CN and triazine-based CN. With structural and morphological merits, the ms-CN-0.5 photocatalyst exhibits remarkable adsorption–photodegradation performance for high-level methylene blue (MB). Moreover, simultaneously enhanced photocatalytic reaction rate of Cr­(VI) reduction and MB oxidation over ms-CN-0.5 are achieved and systematically investigated, which benefits from improved crystallinity, increased visible-light absorption, and promoted charge-carrier separation via one-dimensional heterojunction nanorods. On the basis of the reactive species study, a synergistic reduction–oxidation elimination mechanism is revealed, indicating that the photogenerated holes are primary active species for MB degradation, which are rapidly scavenged by MB in the Cr­(VI)/MB coexisting solution, and the photoexcited electrons are responsible for the reduction of Cr­(VI). Our work may provide new insight into the future design of efficient polymeric materials toward practical applications in the environment and energy chemistry.