Operando Investigation of Mechanochemically Synthesized Ni-Based Metal-Organic Frameworks for Electrocatalytic...

A nickel-based metal-organic framework (Ni-MOF) with mixed N- and O-donor linkers was synthesized via both mechanochemical and solvothermal routes and evaluated as an electrocatalyst for alcohol oxidation reactions (AORs). Despite having identical crystal and electronic structures, the mechanochemically synthesized Ni-MOF (termed as MC-MOF) exhibited markedly superior catalytic activity compared to its solvothermally synthesized analog (ST-MOF). Structural characterization confirmed that enhanced performance arises from the distinct morphology and higher density of accessible Ni active sites in MC-MOF. Specifically, the MC-MOF exhibited a roughly 4.4-fold higher electrochemically active surface area, enabling the highly stable, selective oxidation of various alcohols to valuable products over 24 h of continuous operation. Operando quick X-ray absorption spectroscopy revealed that under alkaline conditions, MC-MOF undergoes potential-dependent structural evolution, displaying distinct catalytic pathways for oxygen evolution and AORs. While Ni centers oxidize to higher valence states during the oxygen evolution reaction, they remain largely in the Ni²⁺ state during AORs, indicating selective suppression of high-valent Ni-oxygenated species in the presence of alcohol molecules in the electrolyte medium. This study demonstrates that mechanochemical synthesis can effectively tailor the morphology and catalytic behavior of MOF-based electrocatalysts, offering an environmentally benign and scalable route for developing advanced materials for sustainable energy conversion.