Low‐Coordinate Iridium Oxide Confined on Graphitic Carbon Nitride for Highly Efficient Oxygen Evolution

Highly active and durable electrocatalysts for the oxygen evolution reaction (OER) is greatly desired. Iridium oxide/graphitic carbon nitride (IrO 2 /GCN) heterostructures are designed with low‐coordinate IrO 2 nanoparticles (NPs) confined on superhydrophilic highly stable GCN nanosheets for efficient acidic OER. The GCN nanosheets not only ensure the homogeneous distribution and confinement of IrO 2 NPs but also endows the heterostructured catalyst system with a superhydrophilic surface, which can maximize the exposure of active sites and promotes mass diffusion. The coordination number of Ir atoms is decreased owing to the strong interaction between IrO 2 and GCN, leading to lattice strain and increment of electron density around Ir sites and hence modulating the attachment between the catalyst and reaction intermediates. The optimized IrO 2 /GCN heterostructure delivers not only by far the highest mass activity among the reported IrO 2 ‐based catalysts but also decent durability.