Spectroscopic Characterization of Highly Active Fe–N–C Oxygen Reduction Catalysts and Discovery of Strong Interaction with Nafion Ionomer,ACS Applied Energy Materials

当前位置： X-MOL 学术 › ACS Appl. Energy Mater. › 论文详情

Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)

Spectroscopic Characterization of Highly Active Fe–N–C Oxygen Reduction Catalysts and Discovery of Strong Interaction with Nafion Ionomer
ACS Applied Energy Materials ( IF 5.4 ) Pub Date : 2023-12-28 , DOI: 10.1021/acsaem.3c02522
Roman Ezhov ₁ , Olga Maximova ₁ , Xiang Lyu ₂ , Denis Leshchev ₃ , Eli Stavitski ₃ , Alexey Serov ₂ , Yulia Pushkar ₁

Affiliation

Scaling up clean-energy applications necessitates the development of platinum group metal (PGM)-free fuel cell electrocatalysts with high activity, stability, and low cost. Here, X-ray absorption (XAS) at the Fe K-edge and Fe K_β X-ray emission (XES) spectroscopies were used to study the electronic structure of Fe centers in highly active Fe–N–C oxygen reduction catalysts with significant commercial potential. X-ray absorption near-edge structure (XANES) analysis has shown that the majority (>95%) of Fe centers are in the Fe³⁺ oxidation state, while extended X-ray absorption fine structure (EXAFS) detected a mixture of single site Fe–N₄ centers (>95%) and centers with short (∼2.5 Å) Fe–Fe interactions of Fe metal and/or Fe-carbide nanoparticles (<5%) featuring the Fe⁰ oxidation state. Surprisingly, addition of Nafion, the most widely used ionomer, resulted in pronounced changes in the XAS spectra, consistent with a strong catalyst–ionomer interaction where long Fe–Fe interactions at ∼3.1 Å were shown to be a feature of Fe³⁺ ions bound with the Nafion. We conclude that exposure to Nafion during the device formulation has a different effect from the aggressive acid leaching typically used in the preparation of Fe–N–C catalysts. It was hypothesized that the polymer interacts with single sites’ Fe³⁺ centers, as well as with graphene layers protecting the Fe⁰ nanoparticles, and extracts some Fe ions into the Nafion matrix.

中文翻译：

高活性 Fe-N-C 氧还原催化剂的光谱表征以及与 Nafion 离聚物强相互作用的发现

扩大清洁能源应用需要开发具有高活性、稳定性和低成本的不含铂族金属（PGM）的燃料电池电催化剂。在这里，Fe K 边缘的 X 射线吸收（XAS）和 Fe K _β X 射线发射（XES）光谱用于研究高活性 Fe-N-C 氧还原催化剂中 Fe 中心的电子结构，具有显着的催化活性。商业潜力。X射线吸收近边结构（XANES）分析表明，大多数（>95%）Fe中心处于Fe ³⁺氧化态，而扩展X射线吸收精细结构（EXAFS）检测到单一的混合物位点 Fe-N _{4中心 (>95%) 和具有 Fe}⁰氧化态的 Fe 金属和/或 Fe-碳化物纳米颗粒 (<5%) 的短 (∼2.5 Å) Fe-Fe 相互作用的中心。令人惊讶的是，添加最广泛使用的离聚物 Nafion 导致 XAS 光谱发生显着变化，这与强催化剂-离聚物相互作用一致，其中~3.1 Å 的长 Fe-Fe 相互作用被证明是 Fe ³⁺离子的特征与 Nafion 绑定。我们得出的结论是，在器件配制过程中暴露于 Nafion 与 Fe-N-C 催化剂制备中通常使用的侵蚀性酸浸具有不同的效果。据推测，聚合物与单位点的 Fe ³⁺中心以及保护 Fe ⁰纳米粒子的石墨烯层相互作用，并将一些 Fe 离子提取到 Nafion 基质中。

更新日期：2023-12-28

点击分享查看原文

点击收藏

阅读更多本刊新发论文本刊介绍/投稿指南