Moderate NaNO 2 etching enables easy crystallinity optimization of g-C 3 N 4 with superior photoreduction performance

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  • Lifeng Cui, University of Shanghai for Science and Technology
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  • Zirou Fang, University of Shanghai for Science and Technology
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  • Yanfei Liu, University of Shanghai for Science and Technology
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  • Mengya Chen, University of Shanghai for Science and Technology
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  • Chaochuang Yin, University of Shanghai for Science and Technology
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  • Junjie Wang, University of Shanghai for Science and Technology
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  • Zegao Wang, College of Materials Science and Engineering, Sichuan University
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  • Mingdong Dong
  • Shifei Kang
  • Ping Liu, University of Shanghai for Science and Technology

As a promising visible-light-responsive catalyst, graphitic carbon nitride (g-C 3 N 4 ) has been widely used in environmental and energy applications owing to its unique semiconducting optoelectronic properties. However, the photocatalytic performance of bulk g-C 3 N 4 synthesized using N-containing precursors via a conventional thermal polycondensation process is generally limited by low crystallinity caused by incomplete polymerization. In addition to forced polymerization under high-pressure conditions, removing the unpolymerized and inactive part of bulk g-C 3 N 4 through controllable etching is another practical way to optimize its crystallinity. Therefore, we developed an economical and general method to fabricate g-C 3 N 4 with high crystallinity and excellent photocatalytic properties, in which cheap sodium nitrite aqueous solution is utilized as a moderate etching agent. The compositions and physiochemical properties of the products were comprehensively investigated by X-ray diffraction, Fourier-transform infrared spectroscopy, ultraviolet visible diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, N 2 adsorption-desorption, and electrochemical impedance spectroscopy measurements. In addition, ToF-SIMS (time-of-flight secondary ion mass spectrometry), a new surface analysis technology, was also used to determine the surface and structural characteristics of all samples. The obtained g-C 3 N 4 shows ideal high-crystallinity features and excellent charge transfer ability, leading to significantly improved Cr(vi) reduction activity under visible light. Moreover, there is only a low content of nitrite residue (63.3 mg g -1 ) in the final g-C 3 N 4 product, indicating that the method employing NaNO 2 , which is widely used in the food industry, is safe and waste-free. Therefore, the new controllable NaNO 2 etching method is cleaner and more efficient than commonly-used corrosion approaches based on strong acids or strong oxidants, and thus affords a new strategy in the regulation and structural design of various catalysts.

Original languageEnglish
JournalInorganic Chemistry Frontiers
Pages (from-to)1304-1311
Number of pages8
Publication statusPublished - 1 May 2019

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