Visible light photocatalytic activity follows the single-slope pseudo-first-order reaction kinetics in pristine ZnO nanorods, while for pure Ag 2 O, a two-slope paradigm is pursued with a higher slope at a later period. For the Ag 2 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 2 O, at both time zones. Improved performance of ZnO/Ag 2 O heterostructures arises initially from the reduced e − /h + recombination rate by the synergistic effect between ZnO and Ag 2 O. At a later phase, metallic Ag is produced, which traps the valence electrons of Ag 2 O nanoparticles and advances the e − /h + separation across the ZnO/Ag 0 / Ag 2 O heterojunction structures, rendering them promptly accessible for dye degradation. At an increased Ag 2 O loading, the photodegradation rate constants boost up in both time zones, and the corresponding crossover time (t C ) between the two phases steadily diminishes, leading toward a unique photocatalytic phenomenon that prevails with a superior rate constant. The optimized ZAO 25 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 −1 , which is ∼26.75 times superior than that of pristine ZnO samples. The metal-induced biphasic photocatalysis phenomena have never been reported earlier.

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ZnO/Ag2O heterostructures, as the functional materials for photodegradation of MB dye under visible light irradiation, have been grown using inexpensive hydrothermal and ultrasonic-assisted synthetic routes. The heterostructures have revealed wurtzite ZnO peaks that demonstrate its highly crystalline and hexagonal structure, as well as the cubic Ag2O peaks. The ZnO/Ag2O photocatalyst has demonstrated two-step dye degradation slopes, with the higher-slope arising later in the process when the metallic-Ag traps the valence electrons of Ag2O nanoparticles and advances e–/h+ separation across the ZnO/Ag0/Ag2O heterojunction structures, making them readily accessible for superior dye degradation.