Lab‐on‐Fiber Operando Deciphering of a MOF Electrocatalyst

Abstract Despite the great success in deploying metal‐organic frameworks (MOFs) as efficient electrocatalysts, the low adoption of operando methods hinders the understanding of underlying mechanism. By leveraging the subtle refractive index evolution, including both the real and the imaginary parts, an entirely new concept of a lab‐on‐fiber operando method and its feasibility for “pristine‐immersion‐operando‐post analysis” of electrocatalyts are demonstrated. Concurrent collection of absorption spectra and surface plasmon resonance is achieved by engineering fiber‐optic waveguides to simultaneously induce guided light attenuation and plasmonic coupling. In situ‐formed Co hydroxide and oxide reactive intermediates in zeolitic imidazolate framework‐67 (ZIF‐67) electrocatalyst are optically identified, which shows its underlying self‐reconstruction conversions at different stages during electrocatalytic oxygen evolution reactions, and address the gap in knowledge concerning whether ZIF‐67 is a precatalyst for real catalyst production. This illuminating operando method offers intriguing opportunities to collect all the observables in a single fiber, provides an exciting potential of a new class of device with long‐sought integration and miniaturization capability, and is expected to enable the electrocatalysis community to conquer challenges with conducting multimodal operando experiments outside the laboratory.