Two-Step Visible Light Photocatalytic Dye Degradation Phenomena in Ag 2 O-Impregnated ZnO Nanorods via Growth of Metallic Ag and Formation of ZnO/Ag 0 /Ag 2 O Heterojunction Structures

• Published in: Langmuir 2022-04, Vol.38 (15), p.4503-4520
• Main Authors: Sahu, Payel, Das, Debajyoti
• Format: Article
• Language: English
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/acs.langmuir.1c02860

Visible light photocatalytic activity follows the single-slope pseudo-first-order reaction kinetics in pristine ZnO nanorods, while for pure Ag O, a two-slope paradigm is pursued with a higher slope at a later period. For the Ag O-impregnated ZnO heterostructured nanorod photocatalyst, the two-step photocatalysis phenomena proceed with dye degradation rate constants emerging higher than those of individual ZnO and Ag O, at both time zones. Improved performance of ZnO/Ag O heterostructures arises initially from the reduced e /h recombination rate by the synergistic effect between ZnO and Ag O. At a later phase, metallic Ag is produced, which traps the valence electrons of Ag O nanoparticles and advances the e /h separation across the ZnO/Ag /Ag O heterojunction structures, rendering them promptly accessible for dye degradation. At an increased Ag O loading, the photodegradation rate constants boost up in both time zones, and the corresponding crossover time ( ) between the two phases steadily diminishes, leading toward a unique photocatalytic phenomenon that prevails with a superior rate constant. The optimized ZAO heterostructure photocatalyst demonstrates ∼96.24% photodegradation of methylene blue (MB) dye within 30 min of visible light exposure, and its degradation rate constant is ∼0.24848 min , which is ∼26.75 times superior than that of pristine ZnO samples. The metal-induced biphasic photocatalysis phenomena have never been reported earlier.