祝贺课题组在尖晶石掺杂取代和结构调控方面再次取得重要突破！祝贺孙静博士在Nano Letters 发表重要学术成果！(DOI: 10.1021/acs.nanolett.1c04425)

Nano Letters封面

       金属离子取代和阴离子交换是调控尖晶石电子结构的两种有效策略。然而，外来金属阳离子的最佳位置以及这些金属和阴离子的确切作用仍然难以捉摸。在此，通过Cr³⁺取代和S^2-交换制备了具有优异OER活性的CoFe₂O₄基空心纳米球。 X射线吸收光谱和理论计算表明，Cr³⁺可以精确掺杂到八面体（Oh）Fe位点，同时诱导Co空位，可以激活相邻的四面体（Td）Fe³⁺。此外，由于压缩应变效应，S^2- 交换导致 Td-Fe 的结构变形。 Td-Fe局部晶体结构的变化导致*OOH中间体偏离y轴平面，从而增强*OOH的吸附。Co空位和S^2-交换可以调整Td-Fe的晶体结构和电子结构，从而激活惰性Td-Fe，提高电化学性能。

Figure 1. (a) Schematic illustration of the synthetic strategy for CFCS; (b) crystal structure of CoFe₂O₄; (c) XRD patterns of CoFe2O4, CFC, and CFCS; SEM images of (d) CoFe2O4, (e) CFC, and (f) CFCS; (g) TEM image, (h) HR-TEM, (i) HAADF-STEM image, and (j−n) elemental mapping results of the CFCS catalyst. 

Figure 2. (a) Mössbauer spectra of the CoFe2O4 and CFCS; (b) PALS; XANES spectra of (c) Co K-edge and (d) Fe K-edge; Fourier-transformed EXAFS k²χ(k) data of (e) Co K-edge and (f) Fe K-edge; (g) scattering path of CFCS Fe K-edge; (h) WT-EXAFS plots of CFCS; (i) Fouriertransformed EXAFS k²χ(k) data of Cr K-edge. 

Figure 3. (a) OER polarization curves, (b) Tafel slopes, (c) Nyquist plots measured at 0.55 V, (d) OER performance comparison of overpotentials at 10 mA·cm⁻² of recently spinel-based catalysts, (e) O₂ faraday efficiency at 350 mV, and (f) chronopotentiometric durability test of the catalyst in 1.0 M KOH solution (inset image shows the LSV curves of CFCS before and after cycles). High-resolution XPS spectra of CFCS electrode cycling at different voltages (0, 0−0.1, 0−0.3, 0−0.5 V): (g) Co 2p and (h) O 1s. (i) Co K-edge XANES spectra for CFCS and cycled at different voltages. 

Figure 4. (a) ORR polarization curves, (b) overall polarization curves of the catalysts for ORR and OER, and (c) peroxide percentage (H₂O₂ %) and the corresponding number of electron transferred. (d) Schematic diagram of Zn−air battery, (e) charge−discharge polarization curves, (f) power density, (g) open-circuit voltage of 1.39 V, (h) the fan powered by a Zn−air battery, and (i) cycling performance. 

Figure 5. Computational structure models of the pristine (a) CoFe2O4, (b) CFC, and (c) CFCS slabs; (d) Gibbs free energy change diagram on Td-Fe site during the OER process; (e, f) standard scaling relationship (ΔG_OOH = ΔG_OH + 3.2) for *OOH and *OH of CoFe2O4, CFC, and CFCS on Td site; (g) partial density of states in the Td Fe site; (h, i) calculated differential charge density around the Td-Fe site in CoFe2O4, CFC, and CFCS (isosurface 0.01 e/bohr.36 Cyan electronic clouds denote loss of electrons and yellow clouds denote gain of electrons).  

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