DOI: https://doi.org/10.1016/j.jpowsour.2024.235821
原文链接：https://www.sciencedirect.com/science/article/pii/S0378775324017737
对于电极材料而言，通过元素掺杂、界面改性等可以有效提升电化学性能，其中掺杂过渡金属（Fe、Co、Ni）原位还原析出纳米颗粒是非常可行的策略，在CO2电解、H2O电解中具有广泛的应用。为了进一步提升性能，对于电极结构，通过电纺丝构筑纳米纤维结构，之后原位析出纳米颗粒，可以进一步提升性能，关于此策略，推荐大家阅读John Irvine教授的两篇文章：
M. Xu, C. Liu, A. B. Naden, H. Früchtl, M. Bühl, J. T. S. Irvine, Electrochemical Activation Applied to Perovskite Titanate Fibers to Yield Supported Alloy Nanoparticles for Electrocatalytic Application. Small 2023, 19, 2204682. https://doi.org/10.1002/smll.202204682；
Xu, M., Cao, R., Wu, S., Lee, J., Chen, D. and Irvine, J.T., 2023. Nanoparticle exsolution via electrochemical switching in perovskite fibers for solid oxide fuel cell electrodes. Journal of Materials Chemistry A, 11(24), pp.13007-13015.
在本篇工作中，研究者通过静电纺丝直接获得 Ni 掺杂的 Sr0.95Ti0.3Fe0.7O3-δ/Ce0.9Gd0.1O2-δ（表示为 STFN/GDCN）纳米纤维复合材料。然后，通过 10%H2/Ar 还原将 Ni 纳米颗粒双脱溶，原位锚定在 STFN 和 GDCN 表面（表示为 Ni@STFN/GDCN），用作 SOEC 阴极。这种复合阴极不仅有利于 CO2 还原反应 (CO2RR) 速率，而且还能抵抗热聚集和碳沉积。Ni@STFN/GDCN 阴极在纯 CO2 中工作，施加电压为 1.6 V，电流密度达到 1.85 A cm−2，超过了其他工作中报告的大多数先进电极。此外，在电流密度为 1.5 A cm−2 的 CO2RR 测试中，180 小时内没有明显的电压波动，表现出优异的长期稳定性。测试结果表明，锚固在异质复合纳米纤维上的原位双脱溶纳米金属是一种可靠、稳定的 SOEC 阴极，可用于直接、高效的 CO2电解。
Fig. 1. (a) Schematic of the fabrication of dual-exsolved Ni@STFN/GDCN composite nanofibers. SEM images of 1: 1 STFN/GDCN composite nanofibers (b) before and (c) after reduction. (d) XRD patterns of STFN/GDCN and Ni@STFN/GDCN samples.
Fig. 2. (a) HRTEM image of the reduced Ni@STFN/GDCN composite nanofiber. Squares A, B and C are the partial magnification for the selected regions of TEM images. (b) HAADF-STEM image and EDS mappings of the reduced nanofiber.
Fig. 3. XPS spectra of (a) Ni 2p, (b) Fe 2p, (c) Ce 3d and (d) O 1s for STFN/GDCN and Ni@STFN/GDCN, (e)Thermogravimetric analyses for the weight variation of STFN/GDCN and Ni@STFN/GDCN exposing in air from room temperature to 800 °C.
Fig. 4. (a) The cross-section image of single cell sandwich structure evaluated by SEM, and the electrochemical performance evaluated at 800 °C by (b) I-V-P curves, (c) EIS spectra, (d) DRT analysis of the EIS spectra shown in (c).
Fig. 5. I-V-P curves (a–b) and EIS spectra (c–d) of cells with STFN/GDCN and Ni@STFN/GDCN as electrodes and testing under different H2 partial pressures at 800 °C, and the corresponding DRT analysis (e) and (f) originated from the EIS spectra in (c) and (d).
Fig. 6. CO2 electrolysis performance of SOECs with STFN/GDCN and Ni@STFN/GDCN as electrodes testing in pure CO2 and at 800 °C. (a) I-V curves, (b) Comparison of the CO2 electrolysis performance with other advance electrode testing at 1.6 V voltage, (c) EIS spectra, (d) potentiostatic tests at different voltages, (e) CO production rate and Faradaic efficiency with applying voltage from 1.0 V to 1.6 V.
Fig. 7. (a) Long-term stability of Ni@STFN/GDCN electrode for CO2RR test with a current density of 1.5 A cm−2 at 800 °C, (b) EIS spectra before and after test, (c) Raman and (d) XPS analysis after test, SEM images of (e) Ni@STFN/GDCN electrode and (f) the cross section of cathode/electrolyte/anode structure, (g) schematic of Ni@STFN/GDCN electrode for CO2RR.
总而言之，采用静电纺丝相转化和原位脱溶技术制备了以Ni@STFN/GDCN纳米纤维为阴极的LSF/GDC阳极负载SOEC。将其用于直接电解CO2，获得了良好的电化学活性和稳定性。Ni纳米颗粒从STFN和GDCN表面双脱溶，不仅增加了氧空穴浓度，而且加速了直接电解CO2的催化活性。Ni@STFN/GDCN电极对CO2电解表现出优异的催化性能，并在高电流密度下具有高稳定性。这项工作表明，具有异质结构的复合纳米纤维为未来高性能、稳定的CO2电解阴极材料提供了一种可行的设计。
