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Selective dissolution is a common corrosion process in dealloying in which an alloy is immersed in acid to remove the active element, leaving behind an inert constituent. We introduce this technique into the treatment of oxide catalysts. A three-dimensionally ordered macroporous LaMnO3 perovskite has been prepared and treated with diluted HNO3 to selectively remove La cations, acquiring a novel γ-MnO2-like material. LaMnO3 is not a satisfactory catalyst on CO oxidation. Upon the removal of La cations, the obtained sample showed a significantly higher CO oxidation catalytic activity (T50=89 °C) than the initial precursor LaMnO3 (T50=237 °C) and ordinary γ-MnO2 (T50=148 °C). A large surface area, a high degree of mesoporosity, excellent low-temperature reducibility, and especially improved surface oxygen species are deduced to be responsible for CO oxidation at lower temperatures.
Si et al. (Tue,) studied this question.