摘要
Electronic states of active sites of catalysts play a key role in determining electrocatalytic performances. Engineering electronic states through decoration of functional entities is an effective way to advance catalyst design. In this work, Au nanocrystal decorated Fe, Co, and Ni based trimetallic metal organic frameworks (MOFs) (termed Au/(FCN)MOFs), grown in-situ on nickel plates (NP), are developed as high performance oxygen evolution reaction (OER) electrocatalysts. At optimal Au nanocrystal decoration, the Au/(FCN)MOF/NP electrode achieves significantly improved OER performances over the (FCN)MOF/NP electrode, lowering η 10 and η 500 from 242 and 340 mV to 216 and 290 mV, respectively, Tafel slope from 42.1 to 31.7 mV dec −1 , and current density decay from 6 to 5% after 50 h operations at an initial current density of 160 mA cm -2 . The enhancement is attributed to the significantly elevated oxidation states of Fe, Co, and Ni, induced by decoration of the Au nanocrystals of high electronegativity, as evidenced with high-resolution X-ray photoelectron spectroscopy and in-situ Raman spectroscopy studies. Furthermore, the main active metal centers are identified with in-situ X-ray absorption spectroscopy study to be Ni and Co, with Fe playing a supporting role to help Ni acquire high valence states to realize enhanced OER activities.