Oxygen-vacancy-rich MOF-derived amorphous Fe–Co–Se–O electrocatalyst for boosting the alkaline oxygen evolution reaction†

Electrochemical water splitting has been a major focus among researchers due to the degradation of fossil fuels. Here, we successfully synthesized an amorphous Fe–Co–Se–O-300 catalyst derived from the precursor FeSe₂@ZIF-67, featuring abundant oxygen vacancies (V_O), through a combination of ambient temperature stirring, hydrothermal treatment and high-temperature annealing. The Fe–Co–Se–O-300 catalyst required only an overpotential of 280 mV to achieve a current density of 10 mA cm⁻². Electron paramagnetic resonance (EPR) testing confirmed the presence of oxygen vacancies. The X-ray photoelectron spectroscopy (XPS) analysis also confirmed the existence of V_O and revealed that during the OER process, electrons transferred from the Fe species to the V_O species and then to the Co species. As a result, the Fe–Co–Se–O-300 catalyst contained more Co²⁺ and Fe³⁺ species, which enhanced its OER performance. The in situ Raman spectra indicated that the Se species were oxidized to SeO₃²⁻ due to the presence of V_O. Further experiments revealed that the surface-absorbed SeO₃²⁻ greatly improved the OER performance of the catalyst. In conclusion, the large number of oxygen vacancies modified the electronic structure of the catalyst and oxidized the Se species, both of which contributed to the enhancement of the OER performance. This work offers an energy-efficient approach for synthesizing non-precious metal catalysts with oxygen vacancies to catalyze the OER process more efficiently.