The researchers first deposit Ir nanoparticles with an average size of 1.7 nm onto a gas diffusion layer. After applying an initial reducing potential of 0.2 V versus the reversible hydrogen electrode (V_RHE), operando X-ray total scattering with pair distribution function (PDF) analysis and small-angle X-ray scattering (SAXS) reveal that the metallic Ir nanoparticles exhibit a decahedral shape with crystalline face-centred cubic and hexagonal close-packed features. By anodically increasing the potential above 1.1 V_RHE iridium oxide starts forming while still co-existing with metallic Ir, with local rutile oxide features but lacking long-range order. These local rutile motifs can extend up to 1 nm and are composed of edge- and corner-connected [IrO₆] units. Under OER-relevant current densities, such as 1.5 V_RHE, iridium is fully oxidized but the lack of long-range crystalline order persists. The increased oxidizing potential induces a contraction in the Ir–O bond length, as also confirmed by X-ray absorption spectroscopy, as well as an increase in atomic mobility.

Original reference: J. Am. Chem. Soc. https://doi.org/10.1021/jacs.4c08149 (2024)

研究人员首先将平均尺寸为 1.7 nm 的 Ir 纳米颗粒沉积到气体扩散层上。在与可逆氢电极 （V_RHE） 相比施加 0.2 V 的初始还原电位后，具有对分布函数 （PDF） 分析和小角 X 射线散射 （SAXS） 的原位 X 射线全散射显示，金属 Ir 纳米颗粒表现出十面体形状，具有晶面中心的立方体和六方紧密堆积特征。通过阳极氧化增加 1.1 V 以上的电位，_RHE 氧化铱开始形成，同时仍与金属 Ir 共存，具有局部金红石氧化物特征，但缺乏长程有序。这些局部金红石基序可以延伸到 1 nm，由边缘和角落连接的 [IrO₆] 单元组成。在与 OER 相关的电流密度（如 1.5 V_RHE）下，铱被完全氧化，但长程晶序的缺乏仍然存在。氧化电位的增加导致 Ir-O 键长收缩，X 射线吸收光谱也证实了这一点，原子迁移率也增加了。

原始参考资料：J. Am. Chem. Soc.https://doi.org/10.1021/jacs.4c08149 （2024）