A coupled Cobalt(II) oxide-Silver Tungstate nano-photocatalyst: Moderate characterization and evaluation of the photocatalysis kinetics towards methylene blue in aqueous solution

[Display omitted] •The boosted photocatalytic activity of CoO-Ag2WO4 with respect to single systems.•Decrease in the Eg-value of coupled system concerning the individual systems.•Decrease in COD of the MB solution during the degradation process.•Comparable MB mineralization during the photodegradation process. The coupled CoO-Ag2WO4 system (CS) was prepared via mechanical mixing of the as-synthesized Ag2WO4 nanoparticles (NPs) and CoO NPs and then characterized by XRD, FTIR, DRS, and FESEM-EDX. The average crystallite size for CoO, Ag2WO4, and the coupled photocatalyst was obtained about 3.7, 49.8, and 35.3 nm by the Scherrer model, and about 42.7, 76.3, and 86.0 nm by the Williamson-Hall model, respectively. The Eg-values were 3.67, 2.99, and 2.81 eV for the CoO, Ag2WO4, and the coupled CoO/Ag2WO4 crystals. A boosted photocatalytic activity of coupled system was observed toward methylene blue (MB), which also depended on the CoO: Ag2WO4 mole ratio, so when this value was 1:2, the highest activity was achieved. Based on triplication measurements, the average k-value of 0.015 ± 0.002 (t1/2 = 46.8 min) was observed for the MB photodegradation based on the absorption spectra obtained. Based on the COD experiment results, the k-value of 0.018 min−1 (t1/2 = 38.5 min) was obtained.