Facet-selective etching by pyridazine toward robust ruthenium-based oxygen evolution catalysts

Stable oxygen evolution reaction (OER) catalyst alternatives to the precious IrO₂ catalysts are of great importance to the next-generation proton-exchange membrane (PEM) electrolyzers. RuO₂-based materials are promising candidates but suffer from low stability under highly anodic potentials. Here, we reported a facet-selective etching strategy to improve the stability of polycrystalline RuO₂ without significantly affecting the activity. The selective etching was enabled by the specific chemisorption of pyridazine (pyd) with contingent N atoms onto the RuO₂ surface. The pyd-RuO₂ catalyst, after etching, exhibited a low overpotential 247 mV at 100 mA·cm⁻² and obvious stability improvement of over 200 h at 100 mA·cm⁻² with only 0.63% Ru loss in acidic conditions. Combining various characterization techniques and theoretical calculations, we revealed that the crystalline RuO₂ (110) facet is favorably etched by the coordination of pyridazine while protecting other surfaces, which significantly enriches the RuO₂ (110) facets toward higher OER stability via the dynamic dissolution and repair mechanism in the ordered manner. This study offers alternative perspectives on the dissolution and stability mechanism of RuO₂ and the facet-selective modulation of nanocrystals by ligand-driven etching.