Mechanism from catalyst to catalysis on Ir segregated SrIrO3 for hydrogen evolution reaction

Understanding the intricate mechanisms from material fabrication to catalytic reaction is crucial in energy chemistry. Herein, we elucidate the underlying mechanisms from catalyst to catalysis on Ir-segregated SrIrO 3 (Ir/SrIrO 3 ) as an efficient hydrogen evolution reaction (HER) catalyst in acidic conditions. During the phosphorization-assisted reduction process, in-situ spectroscopic analysis revealed that hydrogen radicals (H·) from the dissociation of P-H bonds attack the lattice oxygen at edge Ir-O sites, resulting in the segregation of Ir atoms and the formation of robust Ir-O interfacial structures between exsolved Ir clusters and the oxygen sites in SrIrO 3 . These interfacial structures are essential for the high performance of HER, while SrIrO 3 provides structural stability. The protons in the electrolyte are activated at the Ir nanocluster sites, incorporating oxygen in SrIrO 3 through the Ir-O interface, forming a reconstructed Ir-OH structure. This structure maintains both thermodynamic and electrochemical stability by adjusting hydrogen diffusion, embedding, and surface hydrogen coverage to sustain dynamic equilibrium during the catalytic process. Theoretical analysis confirms the necessity of the stable Ir-O interface via Ir- 5d and O- 2p orbital hybridization and hydrogen intercalation, optimizing charge redistribution, hydrogen bond length, and hydrogen adsorption free energy for enhanced HER kinetics. This study provides new insights into catalyst development by elucidating the relationship between catalyst structure and catalytic performance.