Superior bifunctional oxygen electrocatalysts based on Co2MnO4 with mixed site occupancy, Mn-rich surfaces and twin defects
Superior bifunctional oxygen electrocatalysts based on Co2MnO4 with mixed site occupancy, Mn-rich surfaces and twin defects
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DOI：
10.1016/j.cej.2023.146183
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发表时间：
2023-11
影响因子：
15.1
通讯作者：
Jing Li;Xiyu He;Yunzhu Du;Min Jiang;Qiaodan Hu;Jiewei Yin;F. Yang;Junliang Zhang
中科院分区：
文献类型：
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作者：
Jing Li;Xiyu He;Yunzhu Du;Min Jiang;Qiaodan Hu;Jiewei Yin;F. Yang;Junliang Zhang
Co/Mn基尖晶石氧化物是用于氧还原反应（ORR）和析氧反应（OER）的有前途的电催化剂，然而，在一种组合物中同时实现ORR和OER的高活性具有挑战性。在这里，我们报道了通过简单的共沉淀和退火路线合成的具有富锰表面和丰富孪生缺陷的Co2MnO4（C2M），其表现出优异的ORR活性（半波电位E1/2 = 0.830 V）、长ORR耐久性（在0.45 V vs. RHE下进行12小时计时电流测试后保留91％的电流）和低ΔE = 0.767 V在碱性电解液中介于E1/2和E10 mA/cm2之间，这使其在可充电锌空气电池中表现出优异的性能，表现出136 mW/cm2的高峰值能量密度和809.4 mAh/gZn的大比容量。结合全面的实验研究和DFT模拟，我们发现富Mn表面有利于O2的桥吸附，促进ORR中的4电子反应途径，并且晶体结构中的混合位点占据诱导Mn/Co-O轨道杂化，在带隙中形成杂质能级，以促进电荷转移。此外，通过酸处理可以进一步增强双功能性能和 ORR 耐久性，以显示较低的 ΔE= 0.750 V，并在 12 小时内保留 98.5% 的 ORR 电流。这项工作不仅提供了一种有前途的双功能电催化剂，而且为探索适合大规模生产具有高活性表面的电催化剂的简单合成方法提供了新的视角。
Co/Mn-based spinel oxides are promising electrocatalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), however, it is challenging to achieve high activities for ORR and OER simultaneously in one composition. Here, we report Co2MnO4(C2M) with Mn-rich surfaces and abundant twin defects synthesized by a simple coprecipitation and annealing route, which exhibits excellent ORR activity (half-wave potentialE1/2= 0.830 V), long ORR durability (91% current retained after 12 h-chronoamperometry test at 0.45 V vs. RHE) and a low ΔE= 0.767 V betweenE1/2andE10 mA/cm2in alkaline electrolyte, which enables its excellent performances in rechargeable Zn-air batteries showing a high peak energy density of 136 mW/cm2and a large specific capacity of 809.4 mAh/gZn. Combining comprehensive experimental investigations and DFT simulations, we reveal that the Mn-rich surfaces benefit bridge adsorption of O2to promote the 4-electron reaction pathway in ORR, and the mixed site occupancy in the crystal structure induces Mn/Co-O orbital hybridizations to form an impurity energy level in the band gap to facilitate charge transfer. Furthermore, the bifunctional performance and the ORR durability can be further enhanced by acid treatment to show a lower ΔE= 0.750 V and to retain 98.5% ORR current in 12 h. This work provides not only a promising bifunctional electrocatalyst but also a new perspective of exploring simple synthesis method suitable for mass-producible electrocatalysts with highly active surfaces.