Electronic\nSynergistic Effects on the Stability and\nOxygen Evolution Reaction Efficiency of the Mesoporous LiMn<sub>2–<i>x</i></sub>M<sub><i>x</i></sub>O<sub>4</sub> (M =\nMn, Fe, Co, Ni,

Stable porous manganese oxide-based electrodes are essential\nfor\nclean energy generation and storage because of their high natural\nabundance and health safety. This investigation focuses on mesoporous\nLiMn<sub>2–<i>x</i></sub>M<sub><i>x</i></sub>O<sub>4</sub> (where M is Fe, Co, Ni, and Cu and <i>x</i> is 0, 0.1, 0.3, 0.5, and 0.67) electrodes and thin/thick films.\nThe mesoporous electrodes and films are fabricated by coating clear\nand homogeneous ethanol solutions of the salts (LiNO<sub>3</sub>,\n[Mn(OH<sub>2</sub>)<sub>4</sub>](NO<sub>3</sub>)<sub>2</sub>, and\n[M(OH<sub>2</sub>)<sub><i>x</i></sub>](NO<sub>3</sub>)<sub>2</sub>) and surfactants (P123 and CTAB) and calcining at elevated\ntemperature (denoted as F-LiMn<sub>2–<i>x</i></sub>M<sub><i>x</i></sub>O<sub>4</sub>, G-LiMn<sub>2–<i>x</i></sub>M<sub><i>x</i></sub>O<sub>4</sub>, and <i>meso</i>-LiMn<sub>2–<i>x</i></sub>M<sub><i>x</i></sub>O<sub>4</sub>, respectively). The electrochemical\nproperties, stability, and oxygen evolution reaction (OER) performance\nof the F/G-LiMn<sub>2–<i>x</i></sub>M<sub><i>x</i></sub>O<sub>4</sub> electrodes are investigated in alkaline\nmedia using a three electrode setup. The F-LiMn<sub>1.33</sub>M<sub>0.67</sub>O<sub>4</sub> electrodes (where M is Mn, Fe, Co, and Ni)\nexhibit low Tafel slopes of 60, 43, 44, and 32 mV/dec, respectively.\nWhile all the Mn-rich and F-LiMn<sub>2–<i>x</i></sub>Fe<sub><i>x</i></sub>O<sub>4</sub> electrodes degrade via\nMn(VI) disproportionation reaction, the 33% Co electrode shows high\nstability during the OER. The nickel-based electrodes are stable with\nas little as 15% Ni and display excellent OER performance over 25%\nNi, albeit undergoing a transformation that accumulates Ni(OH)<sub>2</sub> species on the electrode surface. Copper in the F-LiMn<sub>2–<i>x</i></sub>Cu<sub><i>x</i></sub>O<sub>4</sub> electrodes is homogeneous at low Cu percentages but forms\na CuO phase above 15% Cu, undergoes degradation, and displays a weak\nOER performance. In short, Co and Ni stabilize the F-LiMn<sub>1.33</sub>Co<sub>0.67</sub>O<sub>4</sub> and F-LiMn<sub>1.7</sub>Ni<sub>0.3</sub>O<sub>4</sub> electrodes, which display excellent OER performance.