Oxygen Vacancy-induced Electron Density Tuning of Fe3O4for Enhanced Oxygen Evolution Catalysis

Despite the tremendous efforts devoted to enhancing the activity of oxygen evolution reaction (OER) catalysts, there is still a huge challenge to deeply understand the electronic structure characteristics of transition metal oxide to guide the design of more active catalysts. Herein, Fe(3)O(4)with oxygen vacancies (Fe3O4-Vac) was synthesized via Ar ion irradiation method and its OER activity was greatly improved by properly modulating the electron density around Fe atoms. The electron density of Fe3O4-Vac around Fe atoms increased compared to that of Fe(3)O(4)according to the characterization of synchrotron-based X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS) spectra, and density functional theory (DFT) calculation. Moreover, the DFT results indicate the enhancement of the desorption of HOO* groups which significantly reduced the OER reaction barrier. Fe3O4-Vac catalyst shows an overpotential of 353 mV, lower than that of FeOOH (853 mV) and Fe3O4(415 mV) at 10 mA cm(-2), and a low Tafel slope of 50 mV dec(-1)in 1 M KOH, which was even better than commercial RuO(2)at high potential. This modulation approach provides us with valuable insights for exploring efficient and robust water-splitting electrocatalysts.

Automated summary

The OER activity of Fe3O4 catalyst was greatly improved by properly modulating the electron density around Fe atoms through synthesizing Fe3O4 with oxygen vacancies. The Fe3O4-Vac catalyst exhibited lower overpotential and lower Tafel slope in 1 M KOH compared to commercial RuO2, showing potential as an efficient and robust water-splitting electrocatalyst.