Rademaker Dana, Tanase Stefania, Hetterscheid Dennis G H
Leiden Institute of Chemistry, Leiden University, 2300 RA, Leiden, The Netherlands.
Van't Hoff Institute for Molecular Sciences, Universiteit van Amsterdam, 1098 XH, Amsterdam, The Netherlands.
ChemSusChem. 2025 May 19;18(10):e202402295. doi: 10.1002/cssc.202402295. Epub 2025 Jan 30.
Electrocatalysis in metal-organic frameworks is an interplay between the diffusion of charges, the intrinsic catalytic rate, and the mass-transport of reactants through the pores. Here a systematic study is carried out to investigate the role of the electrolyte nature and concentration on the oxygen reduction reaction (ORR) with the PCN-224(Co) MOF in aqueous electrolyte. It was found that the ORR activity is slightly influenced by the nature of the ions in solution, providing that the ionic strength is high enough to minimize the resistivity during the measurement. The ORR activity was found to be 1.3-1.5 times lower in lithium acetate compared to sodium acetate, while the ORR activity in cesium acetate was 1.3-1.6 times higher compared to the activity in sodium acetate. Moreover, there was no dependency found of the ORR catalysis on the size of the anion, buffer concentration, or oxygen concentration. These findings suggest that ORR catalysis in PCN-224(Co) is limited by the intrinsic ORR rate at the active site rather than charge transport through the porous structure or substrate transport in the pores. Therefore, optimization of ORR catalysis with this MOF might be achieved by the optimization of the electronics at the cobalt active site.
金属有机框架中的电催化作用是电荷扩散、本征催化速率以及反应物通过孔隙的传质之间的相互作用。在此，开展了一项系统研究，以考察电解质性质和浓度对在水性电解质中使用PCN - 224(Co)金属有机框架进行氧还原反应（ORR）的作用。研究发现，只要离子强度足够高以在测量期间使电阻率最小化，ORR活性受溶液中离子性质的影响较小。结果发现，与醋酸钠相比，在醋酸锂中ORR活性低1.3 - 1.5倍，而与醋酸钠中的活性相比，醋酸铯中的ORR活性高1.3 - 1.6倍。此外，未发现ORR催化作用与阴离子大小、缓冲液浓度或氧浓度有关。这些发现表明，PCN - 224(Co)中的ORR催化作用受活性位点处的本征ORR速率限制，而非通过多孔结构的电荷传输或孔隙中的底物传输。因此，通过优化钴活性位点处的电子性质，可能实现用这种金属有机框架对ORR催化作用的优化。
