Mariano Ruperto G, Wahab Oluwasegun J, Rabinowitz Joshua A, Oppenheim Julius, Chen Tianyang, Unwin Patrick R, Dincǎ Mircea
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Department of Chemistry, University of Warwick, Coventry CV4 7AL, U.K.
ACS Cent Sci. 2022 Jul 27;8(7):975-982. doi: 10.1021/acscentsci.2c00509. Epub 2022 Jul 1.
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 O reduction reaction (ORR) activity of molecularly defined conductive metal-organic frameworks (MOFs) have been very low: ca. -1 mA cm. Here, we use a combination of gas diffusion electrolyses and nanoelectrochemical measurements to lift multiscale O transport limitations and show that the intrinsic electrocatalytic ORR activity of a model 2D conductive MOF, Ni(HITP), has been underestimated by at least 3 orders of magnitude. When it is supported on a gas diffusion electrode (GDE), Ni(HITP) can deliver ORR activities >-150 mA cm and gravimetric HO 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 Ni(HITP) is capable of ORR current densities exceeding -1200 mA cm 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.
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。尽管它们具有高密度的活性位点，但尚不清楚为什么已报道的分子定义的导电金属有机框架（MOF）的氧还原反应（ORR）活性非常低：约为-1 mA/cm²。在这里，我们结合气体扩散电解和纳米电化学测量来消除多尺度氧传输限制，并表明一种二维导电MOF模型Ni(HITP)的本征电催化ORR活性被低估了至少3个数量级。当它负载在气体扩散电极（GDE）上时，Ni(HITP)可以提供大于-150 mA/cm²的ORR活性，并且其重量法过氧化氢电合成速率超过或与先前的多相电催化剂相当。使用扫描电化学池显微镜实现最快可达的传质速率表明，Ni(HITP)能够实现超过-1200 mA/cm²的ORR电流密度，并且其ORR质量活性比在GDE中观察到的至少高130倍。我们的结果直接表明，精确控制多尺度传质对于在分子材料中实现高电流密度电催化至关重要。
