Mn-Ce-Co complex oxide nanoparticles: Hydrothermal synthesis and their catalytic subcritical oxidation of 4,4′-Dibromobiphenyl

► The in situ observation of 4,4′-DBB indicates that in subcritical water it can form a homogenous phases. ► Some Co doping in Mn-Ce complex oxides enhance catalytic activity in subcritical water oxidation of 4,4′-DBB. ► The main intermediate products of oxidative degradation of 4,4′-DBB are benzoic acid and phenol. ► The Ea are 35.92 and 46.69 kJ/mol for 5% Mn0.9Ce1Co0.1 as catalyst and no catalyst on COD. ► With 5% Mn0.9Ce1Co0.1, the oxidative degradation of 4,4′-DBB exceeds 99% at the temperature of 613 K at 25 min.