第一作者：荆淇

通讯作者：郭洪*

单位：云南大学

在可充电锌空气电池（ZABs）等清洁能源技术中，铂基和钌基材料通常用作氧还原反应（ORR）和析氧反应（OER）的电催化剂，但其高成本及催化活性单一阻碍了锌空气电池的大规模应用。因此，开发一种低成本的双功能电催化剂迫在眉睫。非贵金属催化剂，如过渡金属-氮-碳（TM-N-C）催化剂表现出优异的催化性能。TM-N-C结构中的过渡金属具有典型的方形平面D_4h局部对称特性，由于其3d未占满轨道，可以表现出不同自旋状态的3d电子构型。

基于此，云南大学郭洪教授，在国际知名期刊 Chemical Engineering Journal 上发表题为“3d orbital electron engineering in oxygen electrocatalyst for zinc-air batteries”的研究论文。

该研究将酞菁铁和酞菁镍堆叠在氮掺杂多壁碳纳米管的表面，得到(Fe, Ni)@N-MWCNTs。通过Fe-Ni位点协同作用和碳基底提供的电荷优化金属位点3d电子构型，改变其自旋状态。并根据含氧中间体与具有不同3d电子构型的金属阳离子之间的轨道相互作用预测(Fe, Ni)@N-MWCNTs可能表现出良好的双功能催化活性。结合密度泛函理论与实验结果对其催化活性来源进行进一步理解。此外，(Fe, Ni)@N-MWCNTs组装的两种锌空气电池表现出优异的性能和循环稳定性，证明了其应用潜能。该工作对过渡金属催化剂的设计以及理解具有一定的指导意义。

SCHEME 1 (Fe, Ni)@N-MWCNTs is prepared to understand the effect of 3d electron configuration changes on catalytic activity. Experiment and theoretical calculations prove that 3d electron configurations optimization and the charges donated from the carbon substrate can enhance the OER and ORR performance.

通过ZFC测试及其他物相表征表明Fe-Ni位点协同作用和碳基底的外部电荷捐赠成功优化了金属离子的自旋构型。此外，不同自旋状态的金属离子与含氧中间体表现出不同的轨道相互作用，从而成功预测优化电子构型后的电催化剂适合双功能催化。

Fig. 1. (a) XRD patterns and (b) Raman spectrum of the pristine N-MWCNTs, N-MWCNTs, Fe@N-MWCNTs, Ni@N-MWCNTs, and (Fe, Ni)@N-MWCNTs. SEM images and EDS mapping images of (c) N-MWNCTs, (d) Fe@N-MWCNTs, (e) Ni@N-MWCNTs, and (f) (Fe, Ni)@N-MWCNTs. (g) TEM, HAADF-STEM image, and the corresponding EDS mapping images of (Fe, Ni)@N-MWCNTs.

Fig. 2. (a) Fe 2p, (b) Ni 2p, (c) N 1s and (d) C 1s XPS spectra of (Fe, Ni)@N-MWCNTs, Fe@N-MWCNTs, Ni@N-MWCNTs, N-MWCNTs, the pristine FePc, and NiPc. The ×n above the curves represents that the image is magnified by n times in the vertical direction.

Fig. 3. (a) EPR spectra of N-MWCNTs, Fe@N-MWCNTs, Ni@N-MWCNTs, and (Fe, Ni)@N-MWCNTs. (b) χm plots for ZFC and the calculated number of the unpaired electrons in the 3d orbitals of Fe@N-MWCNTs, Ni@N-MWCNTs, and (Fe, Ni)@N-MWCNTs. (c) 3d electron configurations changes of Fe³⁺, Ni²⁺, and Fe²⁺. (d) The possible orbital interaction between cations and the intermediate species of OER and ORR.

要点二：理论与实验相结合

DFT理论计算进一步证明，FePc、NiPc和N-MWCNTs的协同作用可以增强(Fe，Ni)@N-MWCNTs费米能级以下的电子态，优化Fe-Ni位点d带中心以及平衡OER和ORR过程决速步之间的竞争。

Fig. 4. (a) LSV curves of OER at a scan and rotation rates of 5 mV s⁻¹ and 1600 rpm in O₂-saturated 1 M KOH solution and (b) the corresponding Tafel plots. (c) EIS plots of the N-MWCNTs, Fe@N-MWCNTs, Ni@N-MWCNTs, and (Fe, Ni)@N-MWCNTs, with the inset showing the equivalent circuit used for fitting the experimental data (Rs, solution resistance; Rct, charge transfer resistance and CPE, constant phase element). (d) Cdl, overpotential, and Tafel slope before and after 5000 CV cycles and the relative current after 80000 seconds measured by chronoamperometric test at 1.6 V.

Fig. 5. (a) CV curves at a scan rate of 5 mV s⁻¹ in O₂-saturated 0.1 M KOH solution and the dotted line is the CV curves in O₂-saturated 0.1 M KOH with 1.0 M CH₃OH solution. (b) LSV curves of ORR at a scan and rotation rates of 5 mV s⁻¹ and 1600 rpm in O₂-saturated 0.1 M KOH solution and (c) the corresponding Tafel plots. (d) Curves of the electron transfer number and peroxide yield measured by the RRDE at a scan and rotation rates of 5 mV s⁻¹ and 1600 rpm in O₂-saturated 0.1 M KOH solution. (e) Bar plots of relative current after 80000 seconds measured by chronoamperometric test at −0.6 V. (f) The overall LSV curves and the bar plots of ΔE (inset).

Fig. 6. (a) Schematic structure model of (Fe, Ni)@N-MWCNTs, Fe@N-MWCNTs, and Ni@N-MWCNTs from the side and top views. (b) DOS for (Fe, Ni)@N-MWCNTs, Fe@N-MWCNTs, and Ni@N-MWCNTs. (c) PDOS of Fe and Ni sites of (Fe, Ni)@N-MWCNTs, Fe@N-MWCNTs, and Ni@N-MWCNTs. (d) Reaction scheme with the intermediates of OER and ORR. Gibbs free energy diagrams of (e) (Fe, Ni)@N-MWCNTs (Fe sites), (f) Fe@N-MWCNTs, and (g) Ni@N-MWCNTs for the adsorption of intermediates at different voltages.

要点三：在锌空气电池中具有良好应用潜力

(Fe, Ni)@N-MWCNTs组装的水系锌空气电池表现出优异的性能和循环稳定性，驱动的可穿戴柔性锌空气电池在不同弯折角度下表现出良好的充放电循环，并可用作腕带点亮LED灯。

Fig. 7. Performance of rechargeable ZABs assembled with (Fe, Ni)@N-MWCNTs and commercial Pt/C + RuO₂ electrocatalysts. (a) Galvanostatic discharge of aqueous ZABs at 5 mA cm⁻². The inset shows the results tested by a multimeter. (b) Charge and discharge polarization curves and power density plots of aqueous ZABs. (c) Galvanostatic discharge curves of aqueous ZABs at different current densities from 2 mA cm⁻² to 10 mA cm⁻² (d) Galvanostatic discharge curves of aqueous ZABs at 10 mA cm⁻², the specific capacity is calculated by the mass of zinc consumed (inset). (e) Galvanostatic charge and discharge curves of aqueous ZABs at 5.0 mA cm⁻² with the scan rate of 600 s per cycle. The insets show cycling performances at 1st to 10th, 400th to 410th, and 990th to 1000th cycles. (f) Diagram of the wearable flexible ZABs. (g) Galvanostatic charge and discharge curves of wearable flexible ZABs at 1.0 mA cm⁻² with the scan rate of 600 s per cycle. The electrocatalysts loaded in the battery tests from Fig. 7a–e is 0.45 mg cm⁻² and in Fig. 7g is 0.5 mg cm⁻².

郭洪教授简介：云南大学教授，博士生导师，国际科学组织Vebleo协会Fellow，全球学者库 “全球顶尖科学家”，云南省学术带头人，云南大学东陆学者，中国硅酸盐学会固态离子学分会理事（CSSI），国际能源与电化学科学研究院(IAOEES)理事,国际电化学会（ISE）会员，国家科技专家库在库专家。

主持完成国家自然科学基金面上项目、973计划课题项目、云南省重点、教育部重点项目等20余项省部级及以上课题。主要从事电化学储能及环境催化研究。以第一作者及通讯作者在Adv. Mater., ACS Energy Lett., Energy Storage Mater., Adv. Funct. Mater., Nano Energy., Appl. Catal. B-Environ.等学术期刊发表论文100余篇，引用超过6000次，申请及授权30余项中国发明专利。

荆淇，云南大学材料科学与工程专业硕士研究生，目前从事电催化方向的研究。

云南大学郭洪教授课题组常年招收二次电池关键技术及光、电催化方向师资（科研）博士后及优秀青年学者，

联系邮箱：guohong@ynu.edu.cn。