Abstract

This study demonstrates that the catalytic efficiency of manganese oxides in hydrogen peroxide decomposition is governed primarily by the crystalline phase, which sustains controlled and reversible redox cycling, rather than by specific surface area or bulk reducibility alone. Pyrolusite-rich MnO2 synthesized from a nitrate precursor (MnO2-N) exhibited outstanding performance, achieving more than 95% of the theoretical oxygen yield within 15 min, despite its low specific surface area (2.4 m2 & sdot;g-1). In contrast, a high-surface-area bixbyite-rich Mn2O3 catalyst (MnO2-oxa, 47 m2 & sdot;g-1) showed faster initial kinetics but significantly lower overall oxygen yield (72.6%). Structural and redox characterization by XRD, BET, FTIR, and H2-TPR revealed that the superior performance of MnO2-N arises from the stable pyrolusite framework, which enables efficient and reversible Mn4+/Mn3 + redox cycling under oxidative conditions. Radical scavenger experiments indicated that Mn2O3-rich catalysts predominantly follow a hydroxyl radical-mediated pathway, promoting rapid initial reaction rates but limiting oxygen utilization efficiency and long-term stability. Iron oxide catalysts exhibited negligible activity, and no synergistic effects were observed in Mn-Fe oxide combinations. These findings establish that controlled redox cycling within a stable crystalline framework is the key descriptor governing H2O2 decomposition efficiency, providing critical guidance for the rational design of robust, cost-effective catalysts for oxygen generation and advanced oxidation processes.