Iron Doping Optimizes CoFeCr LDH for Ultrasound‐Assisted Water Splitting

Abstract Ultrasound can remove bubbles and significantly enhance the performance of the hydrogen evolution reaction (HER), yet its impact on the oxygen evolution reaction (OER) is minimal. Improving hydrophilicity has been found to address this issue. CoFeCr LDH/NF, a bifunctional electrocatalyst with good hydrophilicity and a nanoflower structure, is synthesized via a hydrothermal method. Hydrophilicity affects the size of bubbles produced, with better hydrophilic electrodes generating smaller, more easily disrupted bubbles. The cavitation effect upon bubble rupture releases heat, breaking water molecules to produce free OH⁻ and promoting the reconstruction of CoFeCr LDH. Additionally, the nanoflower structure of CoFeCr LDH features numerous micropores, enhancing the surface roughness of NF, and resulting in more uniform bubble sizes. Solution convection induced by ultrasound gathers small bubbles into larger ones, which are more easily removed by ultrasound. At 30 mA cm −2 , ultrasound reduces the overpotential for HER and OER by 17 mV and 16 mV, respectively. Enhanced hydrophilicity significantly improves the efficiency of CoFeCr LDH/NF in water electrolysis, especially in OER.