Dynamic active sites in NiFe oxyhydroxide upon Au nanoparticles decoration for highly efficient electrochemical water oxidation

Noble metal decoration is one of the most efficient strategies to boost the performance for water oxidation. However, identifying the role of noble metals and especially the active sites remain a persistent challenge. Here, we report a direct synthesis of Au nanoparticles (NPs) decorated NiFe oxyhydroxides via in-situ electrochemical conversion and a comprehensive study of the activity boost via a combination of systematic experimental and theoretical studies. We found that Fe doping greatly improved the electrical conductivity and the Fe sites were the dominant active centers, collectively responsible for the remarkably enhanced performance in NiFe oxyhydroxide. Upon Au NPs decoration, the content of high-valence Fe/Ni ions was substantially reduced and the formation of surface oxygen vacancy was greatly suppressed. As a result, the dominant active centers transfer to the interfacial Au sites that directly participate in catalyzing water oxidation. Our study presents a fundamental insight into the origin of activity enhancement and especially the active centers in noble metal decorated NiFe oxyhydroxide catalysts. Au nanoparticles decoration could suppress the generation of surface oxygen vacancy and transfer charge to the substrate, and more importantly induce a transfer of the dominant active centers from Fe sites in Ni(Fe)OOH to the interfacial Au sites in Au@Ni(Fe)OOH. The Au@Ni(Fe)OOH catalyst exhibits an impressive activity and outstanding stability for the oxygen evolution reaction. • Au nanoparticles were deposited on Ni(Fe) oxyhydroxides that were obtained after sufficient OER. • The samples after OER were focused to capture useful information of the real active phases. • Au nanoparticle decoration induces a transfer of the dominate active sites.