Marine ferromanganese crusts are considered to be the potential Pt deposits, and recent studies report a strong association between Pt and vernadite in these crusts. However, there are still uncertainties regarding the molecular processes involved in the enrichment of Pt by vernadite. This study investigates the adsorption behavior and molecular-scale immobilization mechanisms of Pt at water/vernadite interfaces through a combination of batch adsorption and desorption experiments, X-ray absorption fine structure (XAFS) analyses, and atomic resolution chemical imaging. Our findings suggest that the Pt enrichment on vernadite is attributed to an isomorphic substitution of Mn by Pt. The extended X-ray absorption fine structure (EXAFS) analysis reveals that Pt undergoes ligand exchange reactions during the enrichment process, and provides a comprehensive explanation of how Pt penetrates into the vernadite structure starting from the surface. Scanning transmission electron microscopy high-angle annular dark field (STEM-HAADF) observations visually confirm the infiltration of Pt atoms into the crystal structure of vernadite. Additionally, we demonstrate that the Pt enrichment in vernadite is a multi-stage chemical process. X-ray absorption near edge structure (XANES) analysis shows that Pt is initially rapidly adsorbed onto the surface of vernadite and then slowly oxidized. Our study provides a detailed understanding of the molecular-scale mechanisms involved in the adsorption of Pt onto vernadite and its subsequent structural incorporation. This knowledge is valuable for gaining insights into the Pt enrichment in marine ferromanganese crusts.

中文翻译：

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Pt在合成蛭石（δ-MnO2）上的同象取代行为：阐明海相铁锰结壳中Pt富集机制的模型反应

海洋铁锰结壳被认为是潜在的铂矿床，最近的研究报告称这些结壳中的铂与斑驳矿之间存在很强的关联。然而，Vernadite 富集 Pt 所涉及的分子过程仍存在不确定性。本研究通过批量吸附和解吸实验、X 射线吸收精细结构 (XAFS) 分析和原子分辨率化学成像相结合，研究了 Pt 在水/蛭石界面上的吸附行为和分子尺度固定机制。我们的研究结果表明，斑驳矿上 Pt 的富集归因于 Pt 对 Mn 的同象取代。扩展X射线吸收精细结构（EXAFS）分析揭示了Pt在富集过程中发生了配体交换反应，并全面解释了Pt如何从表面开始渗透到蛭石结构中。扫描透射电子显微镜高角度环形暗场 (STEM-HAADF) 观察直观地证实了 Pt 原子渗入到了斑鸠菊晶体结构中。此外，我们还证明了斑驳矿中 Pt 的富集是一个多阶段的化学过程。 X射线吸收近边结构（XANES）分析表明，Pt最初被快速吸附到蛭石表面，然后缓慢氧化。我们的研究提供了对 Pt 吸附到蛭石上及其随后的结构掺入所涉及的分子尺度机制的详细了解。这些知识对于深入了解海洋铁锰结壳中的 Pt 富集非常有价值。