A grand challenge for proton exchange membrane electrolyzers is the rational design of oxygen evolution reaction electrocatalysts to balance activity and stability. Here, we report a support-stabilized catalyst, the activated ~200 nm-depth IrW nanochannel that achieves the current density of 2 A cm⁻² at an overpotential of only ~497 mV and maintains ultrastable gas evolution at 100 mA cm⁻² at least 800 h with a negligible degradation rate of ~4 μV h⁻¹. Structure analyses combined with theoretical calculations indicate that the IrW support alters the charge distribution of surface (IrO₂)_n clusters and effectively confines the cluster size within 4 (n≤4). Such support-stabilizing effect prevents the surface Ir from agglomeration and retains a thin layer of electrocatalytically active IrO₂ clusters on surface, realizing a win-win strategy for ultrahigh OER activity and stability. This work would open up an opportunity for engineering suitable catalysts for robust proton exchange membrane-based electrolyzers.

The fatigue behaviour of additively manufactured (AM) 316L stainless steel is investigated with the main emphasis on internal porosity and surface roughness. A transition between two cases of failure are found: failure from defects in the surface region and failure from the internal defects. At low applied load level (and consequently a high number of cycles to failure), fatigue is initiating from defects in the surface region, while for high load levels, fatigue is initiating from internal defects. Porosities captured by X‐ray computed tomography (XCT) are compared with the defects initiating fatigue cracks, obtained from fractography. The fatigue data are synthesised using stress intensity factor (SIF) of the internal and surface defects on the fracture surface.