Mesoporous Mn1.8Fe1.2O4 nanocubes as robust catalysts for water oxidation

• Nanocube Mn1.8Fe1.2O4 is synthesized through simple self-assembly and calcination.
• The Mn1.8Fe1.2O4 has a uniform structure, a high surface area, and a narrow pore size distribution.
• Varying the temperature of calcination leads to different catalytic performance.
• Mn1.8Fe1.2O4 exhibits high oxygen evolution activity and excellent stability.

We report mesoporous Mn1.8Fe1.2O4 nanocubes that are synthesized through simple self-assembly and calcination. By changing the calcination temperature, we investigated the correlation between the nanostructure and catalytic performance of mesoporous Mn1.8Fe1.2O4 catalysts. Mesoporous Mn1.8Fe1.2O4 exhibited high oxygen evolution activity in both the photochemical and cerium (IV)-driven water oxidation systems. The highest initial turnover frequency (TOF) of 4.6 × 10−4 s−1 per metal atom is obtained at neutral pH in photocatalytic water oxidation reaction, compared with those nonporous MnFe2O4, Fe3O4, and Mn3O4. In a cerium (IV)-driven environment, a high TOF of 1.8 × 10−3 s−1 per metal atom is achieved, which is at least two orders of magnitude more active than that of nonporous MnFe2O4. Multiple experimental results (e.g., XRD, FT-IR, SEM, TEM, and XPS) confirmed that mesoporous Mn1.8Fe1.2O4 materials are highly stable. Our results provide a facile method for synthesis of an inexpensive and highly active heterogeneous catalyst for the oxygen evolution reaction.

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