Development of a new carbon xerogel/ZnO/BaSnO3 photocatalyst for solar and visible light photodegradation of salicylic acid

A novel carbon xerogel/ZnO/BaSnO3 photocatalyst was developed, characterized, and evaluated for the photodegradation of salicylic acid (SA) under solar and visible radiation. The development of the proposed photo- catalyst involved the investigation of multiple synthesis parameters, aiming to optimize the photocatalytic activity of the ternary system. The best photocatalytic efficiency was obtained at 5 % w/w BaSnO3, 0.375 g of added tannin, and calcination temperature of 600 degrees C, yielding the 0.375CX/ZnO/BaSnO3 5 % 600 degrees C photo- catalyst. After thorough characterization, it was concluded that the ternary materials are composed of a mixture of crystalline ZnO and BaSnO3 structures and carbon xerogel (CX). Additionally, the ternary materials displayed significant capacity to absorb visible radiation, mostly due to CX addition. Morphology-wise, the 0.375CX/ZnO/ BaSnO3 5 % 600 degrees C was composed of nodular and polyhedral nanometric particles, displaying higher surface area when compared to materials without CX. Through chronoamperometry and electrochemical impedance spectroscopy, it was determined that the optimized ternary material achieved the highest photocurrent generation and lowest charge transfer resistance among the materials evaluated, indicating a superior photocatalytic activity. Photocatalytic tests demonstrated the superiority of the ternary system in the degradation of SA under solar and visible light irradiation, achieving 93 % and 52.3 % degradation after 5 h, respectively. The superior mineralization of SA (72.2 %) achieved by the optimized ternary material under solar radiation further demonstrated its increased efficacy. The suppression methodology allowed for the identification of the hydroxyl radical as the major active species in the SA degradation. A Z-type heterojunction was proposed for the ternary system, based on the staggered band alignment between ZnO and BaSnO3 and the role of CX as a solid-state mediator, possibly leading to effective charge separation and enhanced redox activity. Phytotoxicity tests showed favorable Lactuca sativa growth in SA solutions treated with 0.375CX/ZnO/BaSnO3 5 % 600 degrees C (especially under solar radiation), indicating reduced toxicity.