Tuning the Reconstruction of Metal–Organic Frameworks during the Oxygen Evolution Reaction

Abstract

High Resolution Image Download MS PowerPoint Slide Recently, there has been growing interest in the conversion of metal–organic frameworks (MOFs) into metal-hydroxide catalysts for alkaline oxygen evolution reactions (OERs). While studies have shown that the initial OER performance of MOF-derived intermediates surpasses that of traditional metal-hydroxide catalysts, ongoing debates persist regarding these catalysts' durability and electrochemical stability. Moreover, the inevitable reorganization (aging) of MOF-derived catalysts from disordered to ordered phases, particularly those primarily composed of nickel oxyhydroxides, remains a topic of discussion. To address these issues, we propose a straightforward approach to mitigating MOF reconstruction and modulating aging in harsh alkaline environments by introducing additional organic carboxylate linkers into electrolytes. Specifically, we focus on two examples: Ni-BPDC-MOFs and NiFe-BPDC-MOFs, of formula [M 2 (OH) 2 BPDC] (M: Ni and Fe; BPDC = 4,4′-biphenyldicarboxylate). Experimental results indicate that alkaline electrolytes containing additional BPDC linkers exhibit enhanced OER activity and a prolonged electrochemical lifespan. Complemented by in situ Raman spectroscopy, our findings suggest that manipulating the coordination equilibrium of the organic linker involved in Ni-MOF formation (linker assembly) and reconstruction (linker leaching) leads to the formation of more disordered nickel oxyhydroxide phases as the active catalyst material, which shows enhanced OER performance.