Molecular materials must deliver high current densities to be competitive with traditional heterogeneous catalysts. Despite their high density of active sites, it has been unclear why the reported O₂ reduction reaction (ORR) activity of molecularly defined conductive metal–organic frameworks (MOFs) have been very low: ca. −1 mA cm^–2. Here, we use a combination of gas diffusion electrolyses and nanoelectrochemical measurements to lift multiscale O₂ transport limitations and show that the intrinsic electrocatalytic ORR activity of a model 2D conductive MOF, Ni₃(HITP)₂, has been underestimated by at least 3 orders of magnitude. When it is supported on a gas diffusion electrode (GDE), Ni₃(HITP)₂ can deliver ORR activities >−150 mA cm^–2 and gravimetric H₂O₂ electrosynthesis rates exceeding or on par with those of prior heterogeneous electrocatalysts. Enforcing the fastest accessible mass transport rates using scanning electrochemical cell microscopy revealed that Ni₃(HITP)₂ is capable of ORR current densities exceeding −1200 mA cm^–2 and at least another 130-fold higher ORR mass activity than has been observed in GDEs. Our results directly implicate precise control over multiscale mass transport to achieve high-current-density electrocatalysis in molecular materials.

中文翻译：

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使用导电 MOF 将 O2 电还原率提高一千倍

分子材料必须提供高电流密度才能与传统的多相催化剂竞争。尽管它们的活性位点密度很高，但目前尚不清楚为什么报告的分子定义的导电金属-有机框架 (MOF) 的 O ₂还原反应 (ORR) 活性非常低：约。-1 毫安厘米^–2。在这里，我们结合使用气体扩散电解和纳米电化学测量来提升多尺度 O ₂传输限制，并表明模型 2D 导电 MOF Ni ₃ (HITP) ₂的固有电催化 ORR 活性被低估了至少 3 个数量级量级。当它被支撑在气体扩散电极 (GDE) 上时，Ni ₃(HITP) ₂可以提供 >-150 mA cm ^–2的 ORR 活性和重量 H ₂ O ₂电合成速率，超过或与之前的非均相电催化剂相当。使用扫描电化学电池显微镜强制实现最快的质量传输速率表明，Ni ₃ (HITP) ₂的 ORR 电流密度能够超过 -1200 mA cm ^–2，并且 ORR 质量活性至少比 GDE 中观察到的高 130 倍. 我们的结果直接暗示了对多尺度质量传输的精确控制，以实现分子材料中的高电流密度电催化。