MOF Derived Phosphide Nanocubes with Internal Heterojunction: A Study Powered by Single Entity Electrochemistry

Metal–organic frameworks (MOFs) and their derivatives have captivated immense interest due to their tunable chemical composition and structures. Our research introduces an elegant strategy for advancing hybrid MOF-based electrocatalysts, employing scanning electrochemical cell microscopy (SECCM) for single-entity electrochemistry probing of individual particles with precisely engineered compositions and structures. We achieved controlled phosphidation of Prussian blue analogues, forming hollow nanocubes with Fe-doped CoP/Co2P heterojunctions, which demonstrated significantly enhanced hydrogen evolution reaction (HER) activity, emphasizing the pivotal role of structural and compositional tuning in transition metal phosphide catalysts. Utilizing SECCM, we probed the intrinsic HER activity of individual nanocubes, correlating their electrochemical behavior with their size and composition. Computational insights revealed that the heterojunctions enhanced the electronic conductivity and spin density, established internal electric fields, and minimized the Gibbs free energy barrier. This study paves the way toward advanced nanostructured electrocatalysts, underscoring the crucial interplay between size, structure, composition, and catalytic efficacy.