Vacancies boosting strategy enabling enhanced oxygen evolution activity in a library of novel amorphous selenite electrocatalysts

[Display omitted] •A vacancy-boosting strategy has been present in a library of novel selenite electrocatalysts.•All Fe-based sample delivers amorphous structure with rich oxygen/selenium vacancies.•The resulting Ni1Fe1SeO amorphous sample exhibits outstanding OER activity – and excellent stability.•The amorphous structure with abundant oxygen/selenium vacancies drastically decreases the energy barrier during the OER process. Transition metal selenites are promising in catalytic field, but their oxygen evolution reaction (OER) performance and the corresponding catalysis mechanism has rarely been reported. Here, we report a vacancy-boosting strategy to realize enhanced activity in a library of novel selenite electrocatalysts. Unexpectedly, we found that all Fe-based sample of this series delivers amorphous structure with rich oxygen/selenium vacancies compared to their crystalline counterparts. Consequently, the amorphous Ni1Fe1SeO sample displays outstanding OER activity with an overpotential of 257 mV at 10 mA cm−2, low Tafel slop of 34 mV·dec−1 and excellent stability. X-ray absorption near edge structure (XANES), electron paramagnetic resonance (EPR) characterizations and density functional theory (DFT) calculation reveal the amorphous structure with abundant oxygen/selenium vacancies drastically decreases the energy barrier during the OER process. Our study provides a library of novel OER electrocatalysts from amorphous metal selenites with superior activity through the vacancy-boosting strategy.