Water electrolysis is a crucial technology for clean hydrogen production, but its widespread adoption is hindered by the high cost and low efficiency of oxygen evolution reaction (OER) catalysts, especially in acidic media. This paper introduces a highly efficient and stable Ru-Ir nanocoral (RuIr-NC) catalyst for overall water splitting in acid. RuIr-NC, composed of 3 nm-thick sheets with only 6 at.% Ir, exhibits superior intrinsic activity and stability compared to other OER catalysts. A water-splitting cell using RuIr-NC as both electrodes achieves 10 mA cm⁻²geo at 1.485 V for 120 h without degradation, surpassing existing cells. Operando spectroscopy and atomic-resolution microscopy reveal that the high performance stems from the {0001} facets' resistance to the formation of dissolvable metal oxides and their ability to stabilize Ru as a long-lived catalyst.
