NiFe-based electrocatalysts have attracted great interests due to the lowp rice and high activity in oxygen evolution reaction (OER). However,t he complex reaction mechanism of NiFe-catalyzedOER has not been fully explored yet. Detection of intermediate species can bridge the gap between OER performances and catalyst component/structure properties.H ere,w ep erformed label-free surface-enhanced Raman spectroscopic (SERS) monitoring of interfacial OER process on Ni 3 FeO x nanoparticles (NPs) in alkaline medium. By using bifunctional Au@Ni 3 FeO x core-satellite superstructures as Raman signal enhancer,wefound direct spectroscopic evidence of intermediate O-O À species.According to the SERS results,Featoms are the catalytic sites for the initial OH À to O-O À oxidation. The O-O À species adsorbed across neighboring Fe and Ni sites experiences further oxidation caused by electron transfer to Ni III and eventually forms O 2 product.

Hybrid nanoparticles combining plasmonic and catalytic components have recently gained interest for their potential use in sunlight‐to‐chemical energy conversion. However, a deep understanding of the structure–performance that maximizes the use of the incoming energy remains elusive. Here, a suite of Au and Pd based nanostructures in core–shell and core‐satellites configurations are designed and their photocatalytic activity for Hydrogen (H2) generation under sunlight illumination is tested. Formic acid is employed as H2 source. Core‐satellite systems show a higher enhancement of the reaction upon illumination, compared to core–shell ones. Electromagnetic simulations reveal that a key difference between both configurations is the excitation of highly localized and asymmetric electric fields in the gap between both materials. In this scheme, the core Au particle acts as an antenna, efficiently capturing visible light via the excitation of localized plasmon resonances, while the surrounding Pd satellites transduce the locally‐enhanced electric field into catalytic activity. These findings advance the understanding of plasmon‐driven photocatalysis, and provide an important benchmark to guide the design of the next generation of plasmonic bimetallic nanostructures.

NiFe‐based electrocatalysts have attracted great interests due to the low price and high activity in oxygen evolution reaction (OER). However, the complex reaction mechanism of NiFe‐catalyzed OER has not been fully explored yet. Detection of intermediate species can bridge the gap between OER performances and catalyst component/structure properties. Here, we performed label‐free surface‐enhanced Raman spectroscopic (SERS) monitoring of interfacial OER process on Ni3FeOx nanoparticles (NPs) in alkaline medium. By using bifunctional Au@Ni3FeOx core‐satellite superstructures as Raman signal enhancer, we found direct spectroscopic evidence of intermediate O‐O− species. According to the SERS results, Fe atoms are the catalytic sites for the initial OH− to O‐O− oxidation. The O‐O− species adsorbed across neighboring Fe and Ni sites experiences further oxidation caused by electron transfer to NiIII and eventually forms O2 product.