4.6 Article

A comparison study of sodium ion- and potassium ion-modified graphitic carbon nitride for photocatalytic hydrogen evolution

Journal

RSC ADVANCES
Volume 11, Issue 26, Pages 15701-15709

Publisher

ROYAL SOC CHEMISTRY
DOI: 10.1039/d1ra01395e

Keywords

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Funding

  1. National Natural Science Foundation of China [21773306, 21273280]

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This study prepared Na-doped and K-doped graphitic carbon nitride (GCN), and found that K had a stronger influence on the structure variation of GCN and interacted more strongly with GCN. Both Na and K could improve the photocatalytic activity of GCN, but K doping caused more significant changes, leading to a significant increase in the H-2 evolution rate.
It is well known that modifying graphitic carbon nitride (GCN) is an imperative strategy to improve its photocatalytic activity. In this study, Na-doped and K-doped graphitic carbon nitride (GCN-Na and GCN-K) were prepared via the simple thermal polymerization of a mixture of melamine and NaCl or KCl, respectively. The structure characterization showed that both Na+ and K+ intercalation could reduce the interlayer distance of GCN and introduce cyano defects in GCN, while K+ apparently had a stronger influence on the structure variation of GCN. The chemical composition data showed that both Na+ and K+ could easily interact with GCN, while K-doping caused a greater change in the C/N ratio than Na-doping. Moreover, compared to GCN-Na-5 (5 represents weight ratio of alkali halide to melamine), the conduction and valence bands of GCN-K-5 both shifted upward based on the electronic and optical measurements. Consequently, GCN-K-5 yielded an H-2 evolution rate around 4 times higher than that of GCN-Na-5 under visible light irradiation (>420 nm). The cation size effect on GCN was proposed to be mainly responsible for the variation in the structure, optical and electronic properties of ion-doped GCNs, and hence the enhanced photocatalytic H-2 evolution. The current work can provide new insight into optimizing photocatalysts for enhanced photocatalytic performances.

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