Sulfur-Doped g-C<sub>3</sub>N<sub>4</sub> Heterojunctions for Efficient Visible Light Degradation of Methylene Blue
Andrés F. Pérez-Torres, Diego Felipe Hernández-Barreto, Valentina Bernal, Liliana Giraldo, Juan Carlos Moreno‐Piraján, Edjan Alves da Silva, Maria do Carmo Martins Alves, Jonder Morais, Yenny Hernández, Marı́a T. Cortés, Mario A. Macías
Abstract
High Resolution Image Download MS PowerPoint Slide The discharge of synthetic dyes from different industrial sources has become a global issue of concern. Enormous amounts are released into wastewater each year, causing concerns due to the high toxic consequences. Photocatalytic semiconductors appear as a green and sustainable form of remediation. Among them, graphitic carbon nitride (g-C 3 N 4 ) has been widely studied due to its low cost and ease of fabrication. In this work, the synthesis, characterization, and photocatalytic study over methylene blue of undoped, B/S-doped, and exfoliated heterojunctions of g-C 3 N 4 are presented. The evaluation of the photocatalytic performance showed that exfoliated undoped/S-doped heterojunctions with 25, 50, and 75 mass % of S-doped (g-C 3 N 4 ) present enhanced activity with an apparent reaction rate constant ( k app ) of 1.92 × 10 –2 min –1 for the 75% sample. These results are supported by photoluminescence (PL) experiments showing that this heterojunction presents the less probable electron–hole recombination. UV–vis diffuse reflectance and valence band-X-ray photoelectron spectroscopy (VB-XPS) allowed the calculation of the band-gap and the valence band positions, suggesting a band structure diagram describing a type I heterojunction. The photocatalytic activities calculated demonstrate that this property is related to the surface area and porosity of the samples, the semiconductor nature of the g-C 3 N 4 structure, and, in this case, the heterojunction that modifies the band structure. These results are of great importance considering that scarce reports are found concerning exfoliated B/S-doped heterojunctions.