Engineering modulated microscale assembly of MOF derived iron/nickel selenide for optimizing the oxygen evolution reaction

Abstract

Formulating hierarchical structures via systematic assembly of MOF-derived electrocatalysts emerges as a potent strategy to dictate the electrocatalytic efficacy of the oxygen evolution reaction. However, research into the microscale implications of assemblies is notably lacking and is critical for bubble modulation along with the OER process. Herein, the MOF assembly process is precisely engineered by adjusting the concentration of lyophilized slurry. This approach enables the accurate modulation of macropores in MOF assemblies at the micrometer scale. Following high-temperature selenization, the assembled composite transforms into a carbon skeleton-supported iron/nickel selenide (FeSe₂/NiSe₂) structure. This structure maintains the integrated architecture and the inherent concentration gradient relationship of the original composition. The OER electrocatalytic performance exhibits a significant dependence on the micrometer-scale dimensions, a relationship that becomes especially pronounced at higher current density. Observations gleaned from optical microscopy, finite element simulations, and extensive experimental evidence underscore the importance of meticulously regulating the microscale assembly of MOF derived electrocatalysts for bubble-dynamics modulation, which is essential for optimizing OER performance.