Two-Dimensional Self-assembly of Unconventional fcc Ru3Ir Nanocrystals for Efficient and Robust Acidic Water Oxidation

Acidic oxygen evolution reaction (OER) catalysts face the fundamental challenge of the trade-off between activity and durability that has not yet been well addressed. Herein, we integrate high activity of nanoparticles and good stability of bulk materials into a "macro-nano" catalyst through twodimensional self-assembling of unconventional fcc phase Ru3Ir nanocrystals. Such catalysts deliver a low overpotential of 190 mV at 10 mA cm-2 and stably maintain this over 400 h or 10,000 potential cycles for acidic OER, surpassing previously reported metallic-based catalysts. Operando X-ray absorption spectroscopy and DFT calculations reveal that the high activity is derived from self-reconstructed surface Ru3IrOx species during OER, which are electronically modulated by the fcc-Ru3Ir substrate and lower the energy barrier of the potential-determining O* -> OOH* step. Control experiments reveal that two-dimensional self-assembled structures significantly enhance the corrosion resistance ability of 2D fcc-Ru3Ir by inhibiting the excessive dissolution of surface Ru3IrOx species during the OER process. This nano-to-macro strategy may provide a guideline for designing efficient and robust catalysts for acidic OER and beyond.