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g-C3N4 Hydrogen-Bonding Viologen for Significantly Enhanced Visible-Light Photocatalytic H-2 Evolution
2018-01-17
ACS Catal. 7(12):8228-8234 Dec 2017

Liu, Ya-Nan; Shen, Cong-Cong; Jiang, Nan; Zhao, Zhi-Wei; Zhou, Xiao; Zhao, Sheng-Jie; Xu, An-Wu

Abstract:
Graphitic carbon nitride (g-C3N4) has recently emerged as a promising metal-free photocatalytic material for the conversion of solar energy into chemical energy under visible-light irradiation. Unfortunately, the photocatalytic activity of g-C3Nis still unsatisfactory due to the serious recombination of photogenerated electron–hole pairs. Here, we develop a strategy to construct a type of g-C3N4-based composite photocatalyst (C3N4/CBV2+), a g-C3Nsurface coupled with a viologen redox mediator (1,1′-bis(4-carboxylatobenzyl)-4,4′-bipyridinium dichloride, denoted as CBV2+) through hydrogen bonds, for enhanced Hproduction from water under visible-light irradiation. The CBV2+ molecules not only provide sites for metal particle formation but also act as an efficient electron transfer mediator to transfer the photoinduced electrons from g-C3Nto platinum nanoparticles (Pt NPs). The vectorial charge transfer results in an efficient spatial separation of electrons and holes in the C3N4/CBV2+ composite photocatalyst and facilitates the photogenerated charge carriers for direct photocatalytic water splitting. When 1 wt % CBV2+ is introduced, the hydrogen production rate of C3N4/CBV2+ dramatically increases up to 41.57 μmol h–1, exceeding 85 times the rate over unmodified g-C3N4 (only 0.49 μmol h–1). It is noted that a negligible loss of photocatalytic activity was observed over continuous irradiation up to 20 h, demonstrating its good stability. The combination of the two emerging functional materials represents a simple but economical and powerful approach for highly effective photocatalytic hydrogen production under visible light irradiation. This study opens a window to rationally develop cost-acceptable materials for more efficient solar energy conversion applications.

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