Ni-doped WS2@WO3 heterojunction for waste-water treatment with enhanced visible-light photocatalytic performance enriched with adsorption

Ni-doped WS
²
@WO
³
heterojunction bifunctional photocatalysts with enhanced adsorption of various WS
²
:WO
³
ratios and Ni contents were synthesized and used for methylene blue removal. (Ni-doped) tungsten oxide was first synthesized by a hydrothermal method and the WS
²
: WO
³
ratio was tuned by its sulfurization/partial oxidation at different temperatures and periods of times. The nanostructured samples were characterized by XRD, BET surface area measurement, FESEM, PL, FTIR spectroscopy, temperature programmed oxidation (TPO), and zeta potential measurement methods. TPO helped finding a mild oxidation temperature of 360°C for the partial oxidation process and also an estimation of sulfide percentage in samples. The optimum ratio of WS2:WO3 of 1: 1.72 was attained at 400°C sulfurization temperature. 8 mol%Ni-doped WS
²
@WO
³
exhibited 99% of MB removal by an integrated photodegradation and adsorption.