Facile fabrication of graphitic carbon nitride/polydopamine/polyurethane foam as a floating photocatalyst for synthetic dye remediation†

Graphitic carbon nitride (GCN) has attracted much interest in photocatalytic wastewater treatment. However, GCN sinks when applied in wastewater and photogenerated electron–hole (e–h) pairs are easily recombined. In this work, a GCN-based floating photocatalyst with polyurethane foam (PUF) as a floating support and polydopamine (PDA) as the immobilization anchor and photogenerated electron acceptor was prepared via a one-step immobilization process. Compared to the sample prepared via a two-step immobilization process (PUF/PDA/GCN-2), the sample prepared through the one-step immobilization process (PUF/PDA/GCN-1) exhibited a more uniform distribution of GCN particles (as confirmed from SEM images) with a GCN loading content (5.0%) four times greater than that for PUF/PDA/GCN-2 (1.3%), as shown in TGA results. Interestingly, the addition of PDA could increase the photocatalytic performance more than twice that of the sample without PDA addition. Moreover, 4.7 × 10⁻⁵ mmol dye could be degraded per mg of catalyst on PUF/PDA/GCN-1, which is superior to several existing GCN-based floating photocatalysts. This phenomenon was triggered by efficient e–h pair separation, as suggested by the photoluminescence (PL) spectrum and uniform small-sized GCN distribution. The interaction mechanism among PUF, PDA, and GCN is also proposed based on FTIR and XPS studies as well as the photocatalytic mechanism. The successful preparation of floating photocatalysts through a cheap and facile route was thus demonstrated and has potential for large-scale commercialization.