MnO2-Ir 纳米线：将超小纳米颗粒尺寸、O 空位和低贵金属负载与改进的氧还原反应活性相结合,Nanomaterials

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MnO2-Ir 纳米线：将超小纳米颗粒尺寸、O 空位和低贵金属负载与改进的氧还原反应活性相结合
Nanomaterials ( IF 4.4 ) Pub Date : 2022-09-01 , DOI: 10.3390/nano12173039
Scarllett L S de Lima ₁ , Fellipe S Pereira ₂ , Roberto B de Lima ₂ , Isabel C de Freitas ₃ , Julio Spadotto ₄ , Brian J Connolly ₄ , Jade Barreto ₅ , Fernando Stavale ₅ , Hector A Vitorino ₆ , Humberto V Fajardo ₇ , Auro A Tanaka ₂ , Marco A S Garcia ₂ , Anderson G M da Silva ₁

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尽管利用氧还原反应 (ORR) 生产清洁能源可以被认为是一种有前途的策略，但这种方法仍然具有挑战性，因为它依赖于高负载的贵金属，主要是铂 (Pt)。因此，人们一直致力于开发新的高效电催化剂，以降低 Pt 含量（例如，通过纳米技术工具或合金化）或在这些系统中完全替代它们。目前的研究表明，通过在低 Ir 负载（1.2 wt.%）下沉积在 MnO _{2纳米线表面上的 1.8 ± 0.7 nm Ir 纳米粒子 (NPs) 可以实现对 ORR 的高催化活性。}有趣的是，我们观察到 MnO ₂-Ir 纳米杂化物对 ORR 具有接近商业 Pt/C（20.0 wt.% Pt）的高催化活性，表明它可以使用简单的合成程序获得有效的性能。相对于商业 Pt/C， MnO ₂ -Ir 电催化剂也显示出改进的稳定性，其中在 50 个反应循环后仅观察到轻微的活性损失。考虑到我们的研究结果，MnO ₂ -Ir 纳米杂化物提供的卓越性能可能与（i）还原的 Mn ³⁺物质的显着浓度有关，导致其表面氧空位浓度增加；(ii) 存在强金属-载体相互作用 (SMSI)，其中 MnO _{x之间的电子效应}和 Ir 可以增强 ORR 过程；(iii) 纳米线表面由 Ir 超小尺寸组成的独特结构，能够暴露高能表面/刻面、高表面体积比及其均匀分散。

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MnO2-Ir Nanowires: Combining Ultrasmall Nanoparticle Sizes, O-Vacancies, and Low Noble-Metal Loading with Improved Activities towards the Oxygen Reduction Reaction

Although clean energy generation utilizing the Oxygen Reduction Reaction (ORR) can be considered a promising strategy, this approach remains challenging by the dependence on high loadings of noble metals, mainly Platinum (Pt). Therefore, efforts have been directed to develop new and efficient electrocatalysts that could decrease the Pt content (e.g., by nanotechnology tools or alloying) or replace them completely in these systems. The present investigation shows that high catalytic activity can be reached towards the ORR by employing 1.8 ± 0.7 nm Ir nanoparticles (NPs) deposited onto MnO₂ nanowires surface under low Ir loadings (1.2 wt.%). Interestingly, we observed that the MnO₂-Ir nanohybrid presented high catalytic activity for the ORR close to commercial Pt/C (20.0 wt.% of Pt), indicating that it could obtain efficient performance using a simple synthetic procedure. The MnO₂-Ir electrocatalyst also showed improved stability relative to commercial Pt/C, in which only a slight activity loss was observed after 50 reaction cycles. Considering our findings, the superior performance delivered by the MnO₂-Ir nanohybrid may be related to (i) the significant concentration of reduced Mn³⁺ species, leading to increased concentration of oxygen vacancies at its surface; (ii) the presence of strong metal-support interactions (SMSI), in which the electronic effect between MnO_x and Ir may enhance the ORR process; and (iii) the unique structure comprised by Ir ultrasmall sizes at the nanowire surface that enable the exposure of high energy surface/facets, high surface-to-volume ratios, and their uniform dispersion.

更新日期：2022-09-01

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