Significant advancements towards enhancing the catalytic activity of spinel ferrites in oxygen evolution reaction (OER) have been achieved, however, further studies are required on this regard. In this study, Cr-doped spinel ferrite (NiFeO) embedded in N-doped C (Cr-NiFeO@NC) was synthesized via a high-temperature treatment using an NiFe Prussian blue analog as a precursor and KCrO as a Cr source. Owing to the strong octahedral site preference energy, Cr ions were successfully doped into octahedral sites and tailored the electronic configuration of NiFeO, as confirmed by XPS. The Cr-substituted Cr-NiFeO@NC exhibited the overpotential of 241 mV at 10 mA cm, which was smaller than that of NiFeO@NC (266 mV) at the same current density. Meanwhile, the Tafel slope of Cr-NiFeO@NC (65.32 mV dec) was also lower than that of NiFeO@NC (86.96 mV dec). Therefore, the Cr substitution can improve the electrocatalytic OER performance of NiFeO@NC. In particular, an assembled rechargeable Zn-air battery using Cr-NiFeO@NC as the cathode catalyst afforded a high power density (61.1 mA cm) together with a high specific capacity (740 mA g). Amazingly, it could power light-emitting diodes, demonstrating its real-world application. Density functional theory calculations revealed that Cr ion doping led to electron transfer in NiFeO, resulting in a density of electronic states close to the Fermi level, which probably regulated the adsorption/desorption behaviors of oxygenate intermediates (*O and *OOH), thus promoting the reaction kinetics of the OER. This study provides a helpful basis for the development of spinel oxides with high electrocatalytic OER activity and durability via cation doping.

中文翻译：

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Cr掺杂剂调节NiFe尖晶石氧化物的d轨道电子构型以改善锌空气电池中的析氧反应

在提高尖晶石铁氧体在析氧反应（OER）中的催化活性方面已经取得了重大进展，但是，这方面还需要进一步研究。在这项研究中，使用 NiFe 普鲁士蓝类似物作为前驱体，KCrO 作为 Cr 源，通过高温处理合成了嵌入 N 掺杂 C 中的 Cr 掺杂尖晶石铁氧体 (NiFeO) (Cr-NiFeO@NC)。 XPS 证实，由于具有强的八面体位点偏好能量，Cr 离子成功掺杂到八面体位点中并定制了 NiFeO 的电子构型。 Cr取代的Cr-NiFeO@NC在10 mA cm下表现出241 mV的过电位，小于相同电流密度下NiFeO@NC的过电位（266 mV）。同时，Cr-NiFeO@NC (65.32 mV dec) 的塔菲尔斜率也低于 NiFeO@NC (86.96 mV dec)。因此，Cr取代可以提高NiFeO@NC的电催化OER性能。特别是，使用 Cr-NiFeO@NC 作为阴极催化剂的组装可充电锌空气电池提供了高功率密度（61.1 mA cm）和高比容量（740 mA g）。令人惊讶的是，它可以为发光二极管供电，展示了其在现实世界中的应用。密度泛函理论计算表明，Cr离子掺杂导致NiFeO中的电子转移，导致电子态密度接近费米能级，这可能调节含氧中间体（*O和*OOH）的吸附/解吸行为，从而促进OER 的反应动力学。这项研究为通过阳离子掺杂开发具有高电催化OER活性和耐久性的尖晶石氧化物提供了有用的基础。