Crystalline-Amorphous IrO Supported on Perovskite Nanotubes for pH-Universal OER

Designing catalysts with desirable oxygen evolution reaction (OER) performance under pH-universal conditions is of great significance to promote the development of hydrogen production. Herein, we successfully synthesized a crystalline-amorphous IrO supported on perovskite oxide nanotubes to obtain IrO@La_0.6Ca_0.4Fe_0.8Ni_0.2O₃ with superior OER performance in whole pH media. The overpotential of the IrO@La_0.6Ca_0.4Fe_0.8Ni_0.2O₃ catalyst in media of pH 14, 7.2, and 1 has been demonstrated to be 120, 400, and 143 mV, respectively, with no significant element dissolution as well as double-layer capacitance decay after the durability test. Through comparative experiments with IrO@CNT and the physical mixture of IrO and La_0.6Ca_0.4Fe_0.8Ni_0.2O₃, it is found that the strong metal-support interaction (SMSI) in IrO@La_0.6Ca_0.4Fe_0.8Ni_0.2O₃ makes IrO exist in an amorphous state rich in Ir³⁺, which is closely associated with the surface-active species Ir-OH. Through the regulation of Ir by a perovskite oxide support at the heterointerface, the reaction breaks through the limitation of the adsorbate evolution mechanism (AEM) and converts to a lattice-oxygen-mediated mechanism (LOM), which was fully demonstrated by the addition of the probe tetramethylammonium cation (TMA⁺), a LOM reaction intermediate, to the electrolyte. This work fills the research gap of perovskite oxide supported Ir-based catalysts with heterogeneous structures, providing an excellent strategy for the structural design of efficient pH-universal OER catalysts for hydrogen production systems.