Amorphous-crystalline interface coupling induced highly active ultrathin NiFe oxy-hydroxide design towards accelerated alkaline oxygen evolution.

[Display omitted] • Amorphous-crystalline interface coupling deign is proposed for active OER catalyst. • It is demonstrated by crystalline Fe 2 O 3 supported ultrathin amorphous NiFe(OH) x. • Reduced surface charge accumulation and promoted high valence Ni state is confirmed. • Enhanced OER activity is achieved in AEM electrolyzer at high current density. Amorphous NiFe-based oxyhydroxides can provide abundant active sites for oxygen evolution reaction (OER) in alkaline water splitting, but their disordered atomic arrangement leads to severe charge accumulation and electrochemical polarization at high current density. To address this issue, a crystalline Fe 2 O 3 supported ultrathin amorphous NiFe oxy-hydroxide amorphous-crystalline interface coupling design is proposed. In this design, the interfacial Fe3+ in Fe 2 O 3 as a strong Lewis acid is conducive for trapping the electrons in amorphous NiFe(OH) x , reducing the surface charge accumulation, electrochemical polarization, and improves its OER performance. Meanwhile, in-situ Raman, in-situ IR and XPS analysis reveal that, the electrons transfer is accompanied with Ni2+ oxidation into the highly OER active Ni3+ species. Benefited from this design, the OER overpotentials of the resulting NiFe(OH) x /Fe 2 O 3 NAs catalyst are measured to be 111 and 233 mV at 10 and 100 mA cm−2, respectively, superior than many reported OER electrocatalysts. The anion exchange membrane water electrolyzer using NiFe(OH) x /Fe 2 O 3 NAs delivers a current density of 600 mA cm−2 at a small cell voltage of 1.75 V, and exhibits excellent stability performance in high-current–density condition. This work provides a promising alternative strategy for the development of high-performance amorphous OER catalysts. [ABSTRACT FROM AUTHOR]