Tuning the hybridization state of Ir-O to improve the OER activity and stability of iridium pyrochlore via Zn doping

Developing high-active, stable, and cost-efficient electrocatalysts for oxygen evolution reaction (OER) is urgent task in water splitting. Recently, iridium pyrochlores (A 2 Ir 2 O 7 ) have attracted broad attention as promising catalysts due to their unique electronic properties and the less iridium content relative to IrO 2 , while in iridium pyrochlores, the relatively high concentration of oxygen vacancies decreases the Ir-O hybridization, hindering the OER process. The electronic states of iridium-based pyrochlore M 2 Ir 2 O 7 (M = Lu, Pr) are rationally tuned through partial substitution in A-site of Zn 2+ for Lu 3+ or Pr 3+ , efficiently promoting its intrinsic activity. The optimal Pr 1.8 Zn 0.2 Ir 2 O 7 and Lu 1.8 Zn 0.2 Ir 2 O 7 electrocatalysts exhibit 114.6 and 135.32 A g Ir −1 high mass activity at 1.58 V vs. RHE. Combining X-ray absorption spectrum with DFT calculations , we demonstrate that the doping of Zn 2+ reduces the defective oxygen and regulates the electron distribution . The decrease of defective oxygen leads to the O-2p band center upshift, resulting in the Ir–O covalency promotion and the decrease of the binding energy between oxygen intermediates and Ir to accelerate the OER process. This work provides a fresh idea introducing small ionic radius Zn to solve the problem of high concentration of oxygen vacancies inevitably produced in the synthesis of pyrochlores.