Iridium-Based Cubic Nanocages with 1.1-nm-Thick Walls: A Highly Efficient and Durable Electrocatalyst for Water Oxidation in an Acidic Medium

We report a highly active and durable water oxidation electrocatalyst based on cubic nanocages with a composition of Ir44Pd10, together with well-defined {100} facets and porous walls of roughly 1.1nm in thickness. Such nanocages substantially outperform all the water oxidation electrocatalysts reported in literature, with an overpotential of only 226mV for reaching 10mAcm(geo)(-2) at a loading of Ir as low as 12.5 mu g(Ir)cm(-2) on the electrode in acidic media. When benchmarked against a commercial Ir/C electrocatalyst at 250mV of overpotential, such a nanocage-based catalyst not only shows enhancements (18.1- and 26.2-fold, respectively) in terms of mass (1.99Amg(Ir)(-1)) and specific (3.93mAcm(Ir)(-2)) activities, but also greatly enhanced durability. The enhancements can be attributed to a combination of multiple merits, including a high utilization efficiency of Ir atoms and an open structure beneficial to the electrochemical oxidation of Ir to the active form of IrOx.