Insight into heterogeneous Fenton-sonophotocatalytic degradation of nitrobenzene using metal oxychlorides

•UV/US double irradiation with H2O2 (5 mM) as an oxidant is a successful approach for the degradation of NB using metal oxychlorides as catalysts.•Performance of oxychlorides follows the order FeOCl > CuOCl > BiOCl > ZnOCl.•The synergistic effect plays a vital role through generated reactive radicals besides photo-born holes and electrons.•Synergy is correlated to band gap values, that also dictated the variable activities shown by different metal oxychlorides.•Photo-generated electrons act as degradation inhibitors.