摘要
Manganese-based oxides, particularly spinel Mn 3 O 4 , are promising candidates for alkaline oxygen evolution reaction (OER) catalysts due to their atomic structure, which mimics that of the natural photosynthetic oxygen-evolving complex, and their tunable electronic properties. However, the intrinsic catalytic activity and stability of Mn 3 O 4 remain insufficient for high-performance OER, primarily due to limited oxygen adsorption/desorption capabilities and weak Mn O bonds. In this study, Cu doping is introduced into the tetrahedral sites of the Mn 3 O 4 spinel structure to enhance its catalytic performance. The optimal Cu-doped Mn 3 O 4 catalyst shows a significant reduction in overpotential, from 534 mV to 393 mV at 10 mA cm −2 , along with a decrease in the Tafel slope from 141.9 to 110 mV dec −1 . Additionally, its stability is notably improved, maintaining performance for 130 h compared to just 35 h for undoped Mn 3 O 4 . Experimental results demonstrate that Cu 2+ ions preferentially occupy tetrahedral Mn 2+ sites, which induces an increase in the Mn 3+ content accompanied by the formation of additional oxygen vacancies. This modification not only tunes the electronic structure but also improves charge transfer, electronic conductivity, and the electrochemical surface area. Density functional theory (DFT) calculations reveal that Cu incorporation at tetrahedral sites of Mn 3 O 4 strengthens Mn O d–p hybridization, optimizing the adsorption kinetics of oxygen intermediates and stabilizing the structure, which together enhance both the OER activity and durability. When used as an anode in an anion exchange membrane water electrolyzer (AEMWE), the Cu-doped Mn 3 O 4 exhibits a cell voltage of 2.7 V at 300 mA cm −2 while maintaining excellent stability. This tetrahedral-site doping strategy offers a general approach for enhancing the activity and stability of Mn 3 O 4 and can be extended to other spinel-based OER catalysts.
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