Enhanced Oxygen Evolution Activity at Amorphous Hydroxide/Perovskite\nInterfaces

With\nincreasing focus on sustainable development and clean energy,\nwater electrolysis for hydrogen production is gaining attention as\na green and renewable method. The oxygen evolution reaction (OER)\nat the anode, a four-electron transfer process, limits the efficiency\nof this reaction. In this work, we design an interface consisting\nof amorphous strontium-doped iron hydroxide (Sr–Fe(OH)<sub><i>x</i></sub>) and Ruddlesden–Popper (RP) type\nSr<sub>3</sub>Fe<sub>2</sub>O<sub>7−δ</sub> perovskite\n(SFO<sub>7</sub>) via high concentration NaBH<sub>4</sub> treatment.\nThe formed catalyst (denoted as SFO<sub>7</sub>–S) offers a\n180 mV overpotential at 10 mA cm<sup>–2</sup> and an 18×\nactivity enhancement at a 250 mV overpotential compared to the pristine\nSFO<sub>7</sub>. Electrochemical impedance spectroscopy measurements,\ntetramethylammonium (TMA<sup>+</sup>) tests, and in situ Raman spectroscopy\nstudies reveal that the interfaces between amorphous Sr–Fe(OH)<sub><i>x</i></sub> and SFO<sub>7</sub> perovskite facilitate\nintermediate adsorption and electron transfer, and thus enhancing\nthe overall OER performance via the lattice oxygen pathway. In a membrane\nelectrode assembly electrolyzer using 1 M KOH at 50 °C, SFO<sub>7</sub>–S achieves 200 h stable electrolysis at 300 mA cm<sup>–2</sup> and 1.58 V with a cell degradation rate of 1.3 mV\nh<sup>–1</sup>.