Engineering Amorphous/Crystalline Nanoflower Heterostructures for Enhanced Electrocatalytic Acidic Water Oxidation

Abstract Efficient water electrolysis for green hydrogen production relies on the development of robust oxygen evolution reaction (OER) catalysts, particularly for acidic environments. This study introduces amorphous/crystalline Mn─Ru binary oxides nanoflowers (a/c‐Mn 0.9 Ru 0.1 O 2 ) as a promising acidic OER catalyst, synthesized via a two‐step phase engineering approach. The optimized a/c‐Mn 0.9 Ru 0.1 O 2 ‐200 composition exhibits exceptional OER activity, requiring a low overpotential of 168 mV to achieve a current density of 10 mA/cm 2 and demonstrating remarkable stability over 28 h. This significantly outperforms commercial RuO 2 catalysts, which require an overpotential of 320 mV at 10 mA/cm 2 and exhibit a stability of only 0.5 h under identical conditions. X‐ray absorption spectroscopy (XAS) and X‐ray photoelectron spectroscopy (XPS) analysis results reveal the formation of Mn─O─Ru linkages and an optimized d ‐band electronic structure, attributed to strong electronic coupling at the amorphous/crystalline interface. This unique architecture promotes optimal adsorption/desorption of OER intermediates, leading to enhanced catalytic performance. This study offers a novel strategy for the rational design and production of efficient acidic OER catalysts.