Karst Cave EffectInduced Dandelion-Like Porous Cobalt-Nickel Silicate Hydroxide: Enhanced Oxygen Evolution Reaction Performance via LOM Mechanism.

Enhancing the kinetics and mass transfer efficiency is the central issue in the research of the catalytic oxygen evolution reaction (OER). Here, an in situ hydrothermal transformation method for synthesizing ultra-porous cobalt-nickel silicate hydroxide (CNSH) with a layered double hydroxide (LDH) is demonstrated. This in situ variation from well-crystallized carbonate to amorphous silicate hydroxide leads to a dandelion-like structure originating from framework reconstruction as topotactic transformation process, defined as "karst cave effect". Moreover, the specific coordination environment in CNSH not only enhances Metal-Oxygen Covalency (MOC) for promoting lattice oxygen-mediated mechanism (LOM), but also improves structural stability. CNSH demonstrates superior OER performance, including low overpotentials of 275 mV and 313 mV for current densities of 10 and 100 mA cm-2, respectively, as well as exceptional long-term stability for 800 h at 1 A cm-2. This work provides an innovative and feasible pathway for the rational design of electrocatalysts with both porous structure and rapid kinetics for efficient and stable water oxidation.