Co-based oxides have recently emerged as suitable electrocatalysts for the water oxidation reaction due to their low cost and high activity. Here, we present a comparative study of the electrochemical behavior of pure and metal-ion-substituted cobalt oxides, Co₃O₄(110) and M_xCo_3–xO₄(110), (M = Fe, Ni, Cu; x = 25% and 50%) in order to elucidate the effect of the cation distribution in the surface of the crystal lattice. We have used density functional theory calculations with on-site Coulomb repulsion of the energetics of the oxygen evolution reaction (OER) on these surfaces, and substantial work has been targeted to understand the relation between structure, mechanism, and activity. The activity of the substituted spinels increases relative to that of pure Co₃O₄, with a considerable decrease in overpotential values. This agrees well with the experimental findings. We find the activity of the Co-based oxides toward the OER is in the following order where we have considered that O₂ evolution occurs at the substituent site: Fe_xCo_3–xO₄ (x = 50%) (0.77 V) > pure Co₃O₄ (0.76 V) > Fe_xCo_3–xO₄ (x = 25%) (0.69 V) > Ni_xCo_3–xO₄ (x = 50%) (0.61 V) > Cu_xCo_3–xO₄ (x = 50%) (0.56 V) > Ni_xCo_3–xO₄ (x = 25%) (0.53 V) > Cu_xCo_3–xO₄ (x = 25%) (0.41 V). Our results indicate that 25% Cu-substituted Co₃O₄ has by far the lowest overpotential value of 0.41 V.

中文翻译：

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水氧化对纯铁和（铁，镍和铜）取代的Co ₃ O _4的氧化作用

由于钴基氧化物的低成本和高活性，最近已经出现了作为水氧化反应的合适电催化剂的钴基氧化物。在这里，我们对纯和金属离子取代的钴氧化物Co ₃ O ₄（110）和M _x Co _{3– x} O ₄（110）的电化学行为进行比较研究，（M = Fe，Ni，Cu ；x= 25％和50％），以阐明阳离子在晶格表面的分布效果。我们已经利用密度泛函理论计算对这些表面上的析氧反应（OER）的能量进行了库仑排斥，并且进行了大量工作来理解结构，机理和活性之间的关系。相对于纯Co ₃ O ₄，取代的尖晶石的活性增加，而超电势值则显着降低。这与实验结果非常吻合。我们发现Co基氧化物对OER的活性按以下顺序排列，其中我们认为O _2的演化发生在取代基部位：Fe _x Co_{3– x} O ₄（x = 50％）（0.77 V）>纯Co ₃ O ₄（0.76 V）>铁_x Co _{3– x} O ₄（x = 25％）（0.69 V）> Ni _x Co _{3– x} O ₄（x = 50％）（0.61 V）> Cu _x Co _{3– x} O ₄（x = 50％）（0.56 V）> Ni _x Co _{3– x} O ₄（x = 25％）（0.53 V ）> Cu _x Co _{3– x}O ₄（x = 25％）（0.41 V）。我们的结果表明，25％的Cu取代的Co ₃ O ₄具有最低的0.41 V的超电势值。