Ultrathin metal-organic framework array for efficient electrocatalytic water splitting

TLDR

Two-dimensional metal‑organic frameworks are known for their attractive chemical and structural properties but are typically produced as bulk powders. The study presents a generic method to fabricate ultrathin MOF nanosheet arrays on various substrates via dissolution–crystallization. The fabrication employs a dissolution–crystallization process that yields ultrathin nanosheet arrays. The resulting ultrathin MOF arrays exhibit highly exposed active sites, enhanced conductivity, and hierarchical porosity, enabling a nickel‑iron MOF array to achieve OER with 240 mV overpotential at 10 mA cm⁻², 3.8 s⁻¹ turnover frequency at 400 mV, and stable operation for 20 000 s, while also performing well in HER and overall water splitting.

Abstract

Abstract Two-dimensional metal-organic frameworks represent a family of materials with attractive chemical and structural properties, which are usually prepared in the form of bulk powders. Here we show a generic approach to fabricate ultrathin nanosheet array of metal-organic frameworks on different substrates through a dissolution–crystallization mechanism. These materials exhibit intriguing properties for electrocatalysis including highly exposed active molecular metal sites owning to ultra-small thickness of nanosheets, improved electrical conductivity and a combination of hierarchical porosity. We fabricate a nickel-iron-based metal-organic framework array, which demonstrates superior electrocatalytic performance towards oxygen evolution reaction with a small overpotential of 240 mV at 10 mA cm −2 , and robust operation for 20,000 s with no detectable activity decay. Remarkably, the turnover frequency of the electrode is 3.8 s −1 at an overpotential of 400 mV. We further demonstrate the promise of these electrodes for other important catalytic reactions including hydrogen evolution reaction and overall water splitting.