Atomically dispersed Ru in ZIF-67 as a high-performance HER catalyst: in situ structural evolution and deactivation...

Despite the prevalence of zeolitic imidazolate framework (ZIF-67)-derived catalysts for the hydrogen evolution reaction (HER), the catalytic potential of pristine ZIF-67 remains obscured by its inherent inertness. In this work, we address this gap by developing an annealing-free strategy to implant atomically dispersed noble metals (Ru, Rh, and Pd) into the intact ZIF-67 framework. Remarkably, Ru single-atom modification reduces the HER overpotential of ZIF-67/CC by 252 mV at 10 mA cm^-2 (from 331 mV to 79 mV) and slashes the Tafel slope by 70%, representing the most significant activation of pristine ZIF-67 reported for the HER. Operando studies combined with theoretical calculations uncover an electrochemical reconstruction pathway: during operation, the ZIF-67 skeleton collapses into Co(OH)₂, while Ru atoms aggregate into nanoparticles, causing phase segregation. This transformation excessively strengthens hydrogen adsorption, ultimately degrading performance. Our work establishes single-atom engineering as an effective approach to unlock the latent activity of pristine MOFs while revealing their reconstruction behavior under cathodic conditions.