Improving the Lattice Oxygen Reactivity of Rutile IrO2 via Partial Sn Substitution for Acidic Water Oxidation

The successful deployment of proton-exchange membrane water electrolyzers (PEMWEs) relies on the development of an active and durable electrocatalyst for the anodic oxygen evolution reaction (OER). Although rutile IrO2 shows excellent durability due to its stable crystal structure, it suffers from unsatisfactory activity. Here, we report a partial Sn substitution strategy to trigger lattice oxygen reactivity toward boosted OER. The similar crystal structures of IrO2 and SnO2 promote uniform incorporation of Sn into the lattice of IrO2, thus retaining the durability of the pristine rutile phase. More importantly, the electron transfer from Ir to Sn through the local structure of Ir–O–Sn was found to enhance the Ir–O bond covalency, which in turn activated the lattice oxygen to participate in OER. The enhanced lattice oxygen mechanism (LOM) was further verified by in situ 18O isotope labeling in situ differential electrochemical mass spectroscopy (DEMS). Due to these attributes, the as-designed Ir0.83Sn0.17O2 catalyst showed significantly improved performance, with an overpotential of only 284 mV at a current density of 10 mA cm–2, 38 mV lower than that of the commercial IrO2. In addition, the mass activity of the Ir0.83Sn0.17O2 catalyst reaches as high as 130 A gIr–1 at 1.55 V, which is 2.58 times higher than that of commercial IrO2. Beyond that, the intrinsic stability of the rutile phase endows the Ir0.83Sn0.17O2 catalyst with excellent operational durability. This work provides a novel insight into the improvement of catalyst activity and inspires the design of highly active and stable OER catalysts.