Abstract
The development of photocatalysts that efficiently degrade organic pollutants is an important environmental-remediation objective. To that end, we report a strategy for the ready fabrication of oxygen-doped graphitic carbon nitride (CN) with engendered nitrogen deficiencies. The addition of KOH and oxalic acid during the thermal condensation of urea led to a material that exhibits a significantly higher pseudo-first-order rate constant for the degradation of bisphenol A (BPA) (0.0225 min−1) compared to that of CN (0.00222 min−1). The enhanced photocatalytic activity for the degradation of BPA exhibited by the dual-defect-modified CN (Bt-OA-CN) is ascribable to a considerable red-shift in its light absorption compared to that of CN, as well as its modulated energy band structure and more-efficient charge separation. Furthermore, we confirmed that the in-situ-formed cyano groups in the Bt-OA-CN photocatalyst act as strong electron-withdrawing groups that efficiently separate and transfer photo-generated charge carriers to the surface of the photocatalyst. This study provides novel insight into the in-situ dual-defect strategy for g-C3N4, which is extendable to the modification of other photocatalysts; it also introduces Bt-OA-CN as a potential highly efficient visible-light-responsive photocatalyst for use in environmental-remediation applications.
Highlights
The development of photocatalysts that efficiently degrade organic pollutants is an important environmental-remediation objective
KOH treatment of urea, as a precursor of g-C3N4, promotes alkali-assisted thermal condensation and is an effective method for producing nitrogen defects. This method was used to demonstrate that the band alignment of g-C3N4 can be controlled by the formation of cyano groups and surface nitrogen deficiencies in the g-C3N4 framework, which are preferable for collecting incident visible light and effectively separating photo-generated hole-electron pairs[54]
The X-ray diffraction (XRD) pattern of carbon nitride (CN) exhibits two characteristic peaks at 13.0° and 27.5°, assigned to the (100) and (002) planes, which correspond to in-plane packing and the characteristic interlayer stacking of aromatic systems, respectively[69]
Summary
The development of photocatalysts that efficiently degrade organic pollutants is an important environmental-remediation objective. Qiu et al.[66] developed a simple, low-cost and green method for the synthesis of O-doped porous g-C3N4 by condensing oxalic acid with urea; this material displayed a significantly enhanced ability to efficiently degrade contaminants due to its high specific surface area, efficient charge separation, and its intense visible-light-absorption properties (≈700 nm).
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