Oxygen Vacancy‐induced Electron Density Tuning of Fe₃O₄ for Enhanced Oxygen Evolution Catalysis

Abstract

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 (Fe 3 O 4 ‐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 Fe 3 O 4 ‐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. Fe 3 O 4 ‐Vac catalyst shows an overpotential of 353 mV, lower than that of FeOOH (853 mV) and Fe 3 O 4 (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.