Resolving the three-dimensional structure of transition metal oxide nanoparticles (TMO-NPs), upon self-restructuring from solution, is crucial for tuning their structure–functionality. Yet, this remains challenging as this process entails complex structure fluctuations, which are difficult to track experimentally and, hence, hinder the knowledge-driven optimization of TMO-NPs. Herein, we combine high-energy synchrotron X-ray absorption and X-ray total scattering experiments with atomistic multiscale simulations to investigate the self-restructuring of self-assembled Co-NPs from solution under dark or photocatalytic water oxidation conditions at distinct reaction times and atomic length-scales. Using the atomic range order as a descriptor, we reveal that dissolution of a Co-salt in BO₃ buffer leads to a self-optimization route forming disordered oxyborate Co₃BO_x-NPs unveiling a high oxygen yield due to the formation of surface oxo/hydroxo adsorbates. Those Co₃BO_x-NPs further self-restructure into distorted Co₃O₄-NPs and, lastly, into distorted CoOOH-NPs through a rate-limiting step integrating Co³⁺-states during the course of a representative photocatalytic assay. Self-restructuring does not proceed from amorphous-to-ordered states but through stochastic fluctuations of atomic nanoclusters of ≈10 Å domain size. Our key insight into the structure-selection dynamics of TMO-NPs from solution offers a route for tuning their structure–function relationships for wide-ranging emergent technologies.

中文翻译：

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溶液合成中钴纳米颗粒的结构选择动力学及其对析氧反应的影响


解析过渡金属氧化物纳米颗粒 （TMO-NPs） 从溶液中自我重构后的三维结构对于调整其结构-功能至关重要。然而，这仍然具有挑战性，因为这个过程需要复杂的结构波动，很难通过实验进行跟踪，因此阻碍了 TMO-NPs 的知识驱动优化。在此，我们将高能同步加速器 X 射线吸收和 X 射线全散射实验与原子多尺度模拟相结合，以研究在黑暗或光催化水氧化条件下在不同反应时间和原子长度尺度下从溶液中自组装的 Co-NPs 的自重组。使用原子范围顺序作为描述符，我们揭示了 BO₃ 缓冲液中辅盐的溶解导致形成无序羟硼酸盐 Co₃BO_x-NPs 的自优化路线，由于表面氧代/羟基羟基吸附物的形成而揭示了高氧产率。在代表性光催化测定过程中，这些 Co₃BO_x-NPs 进一步自我重组成扭曲的 Co₃O_4-NPs，最后，通过整合 Co³⁺ 状态的限制步骤自我重组成扭曲的 CoOOH-NPs。自重构不是从无定形到有序状态，而是通过 ≈10 Å 畴大小的原子纳米团簇的随机波动进行。我们从解决方案中对 TMO-NPs 的结构选择动力学的关键见解为调整其结构-功能关系提供了一条途径，适用于广泛的新兴技术。