Highly uniform platinum photodeposited hollow mesoporous titania nanoparticles for photocatalytic degradation of phenol

Abstract

Photocatalysis is an essential and cost-effective method for efficient disinfection and profound detoxification of organic waste from wastewater. In this study, we fabricated an unprecedented facile Pt photodeposited crystalline hollow mesoporous titania nanoparticle (Pt/c-HMTN) module and investigated its photocatalytic efficiency to decompose phenol as a target compound in an aqueous phase. Pt/c-HMTN was produced by a hard template method using silica as a hydrothermally etchable template prior to the facile decoration of the mesoporous titania shell through a modified sol–gel method. Crystallization at 720 °C was performed, followed by Pt photodeposition. The size of Pt/c-HMTN was confirmed to be around 450–500 nm. Comparative experiments between Pt/c-HMTN and c-HMTN exhibited 1.42-fold excellent photocatalytic performance of Pt/c-HMTN compared to c-HMTN, where k_c-HMTN = 0.01946 s⁻¹ and k_Pt/c-HMTN = 0.04458 s⁻¹, an almost 4-fold difference in kinetics. Quantitative analysis regarding catalyst dosage, pH, and temperature was provided additionally. pH revealed the most prominent influence (40% increase in photocatalytic performance, k_pH10 = 0.03400 s⁻¹vs. k_pH7 = 0.01058 s⁻¹) caused by an abundance of hydroxyl radicals at pH 10, whereas temperature variation showed a negligible difference in photocatalytic activity. Furthermore, we have conducted scavenger and stability tests, which included oxidative free radical and hole-trapping tests to investigate a predominant pathway responsible for phenol degradation and the reusability of the catalyst module under continuous pollutant input, respectively. We also elucidated the plausible mechanism of the radical pathway and the role of Pt nanoclusters supported on faceted c-HMTN in photocatalysis. The reaction intermediates have been analyzed and detailed descriptions have been added to provide an overall understanding of the pathway. The samples were characterized using XRD, SEM, TEM, BET, and HPLC to identify the remaining contaminant in the system. In summary, we assure that the Pt/c-HMTN module can be effectively applied in organic contaminant decomposition owing to its superiority in photocatalytic efficiency and reusability.