Heterovalent State and Oxygen Vacancy Defect Structure-Associated V/S Co-Doped SnO for Catalytic Reduction of Organic and Cr Pollutants in the Dark

V/S co-doped SnO bimetal sulfur-oxides catalysts labeled as (Sn,V)(S,O) or (SnVSO) with heterovalent state and oxygen vacancy defect are prepared via a green and facile method. The presence of SnVSO in the heterovalent states of Sn/Sn and V/V facilitates the rapid transfer of the electrons. It improves the electronic charge lifetime, accelerating the efficiency of the catalytic reduction of pollutants. The V/S co-doped SnO regulates the bandgap energy structure. The hydrazine adjusts the heterovalent metal states to reduce Sn to Sn and V to V. Also, it introduces oxygen vacancies to SnVSO to maintain the charge equilibrium and increase the active surface reactive sites, which enhance the catalytic activity. The SnVSO-3 prepared with 0.4 mL hydrazine exhibits excellent catalytic activity, which wholly reduces 20 ppm of 100 mL methyl orange (MO), rhodamine B (RhB), methylene blue (MB), hexavalent chromium (Cr), and 4-nitrophenol (4-NP) within 6 min. In addition, the SnVSO-3 also has good stability after repeated 6 runs with a reduction efficiency of 96.8%. Therefore, the V/S co-doped SnO sulfur oxide catalysts have a promising potential for reducing Cr and organic pollutants.