Constructing oxygen vacancies for δ-MnO2 based monolithic catalyst by Cu intercalation to enhance toluene oxidation

[Display omitted] •Developing a novel molten salt method to in situ construct monolithic catalysts.•Simultaneously achieving of Cu intercalating δ-MnO2 and its loading on Ni foam.•Cu intercalation increases the oxygen vacancy concentration of δ-MnO2. The construction of monolithic catalysts is indispensable for the practical application of thermal catalytic oxidation technology in volatile organic compounds (VOCs) degradation. In this work, a feasible molten salt method is employed to simultaneously construct the Cu intercalated ultrathin δ-MnO2 nanosheet and in situ support it on Ni foam. The resulting monolithic catalyst exhibits a remarkable enhancement on catalytic performance of toluene oxidation compared with the pristine δ-MnO2 supported on Ni foam. Microstructure studies suggest that the interlayer Cu of δ-MnO2 with two-dimensional structure can enhance the disorder of MnO2 lattice, which promotes the formation and exposure of numerous oxygen vacancies and enables lattice oxygen reactivity. Consequently, oxygen activation is improved to generate abundant reactive oxygen species and lattice oxygen is more easily activated, which can accelerate the production and consumption of intermediates during toluene oxidation. This research proposes new insights of designing monolithic catalysts with abundant oxygen vacancies for efficient VOCs oxidation.