Crystalline–Amorphous IrO_x 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 x supported on perovskite oxide nanotubes to obtain IrO x @La 0.6 Ca 0.4 Fe 0.8 Ni 0.2 O 3 with superior OER performance in whole pH media. The overpotential of the IrO x @La 0.6 Ca 0.4 Fe 0.8 Ni 0.2 O 3 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 x @CNT and the physical mixture of IrO x and La 0.6 Ca 0.4 Fe 0.8 Ni 0.2 O 3, it is found that the strong metal–support interaction (SMSI) in IrO x @La 0.6 Ca 0.4 Fe 0.8 Ni 0.2 O 3 makes IrO x exist in an amorphous state rich in Ir 3+, 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.