Crystalline–Amorphous IrO<sub><i>x</i></sub> Supported on Perovskite Nanotubes for pH-Universal OER
Xinyi Li, Ziling Wang, Zijie Peng, Junfang Cheng, Fenghua Zheng, Yuanxing Wang, Yunfeng Tian, Bo Chi, Guanghua Wei, Junliang Zhang
Abstract
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.