Removal and recycling of selenite anions by iron-doped cobalt-based metal organic frameworks for oxygen evolution reaction

Abstract

As the main form exists in selenium-containing wastewater, selenite (SeO32-) is often produced by human activities and is exceedingly difficult to be removed from wastewater. In this study, five iron-doped (Fe-doped) cobalt-based metal organic frameworks (Co/Fe-MOF) with different metal ratios were prepared to remove SeO32- anions. The prepared Co/Fe-MOF were confirmed by characterization and their adsorption properties experiments. They have excellent SeO32- removal performance at pH of 3–8 with a maximum adsorption capacity of 283.11 mg g−1 of Co-MOF. After uptaking SeO32- by Co/Fe-MOF, the used Co/Fe-MOF (U-Co/Fe) contains CoSeO4 and Fe2(SeO4)3 and can be used as electrocatalytic oxygen evolution catalysts. Their oxygen/selenium vacancies can reduce the overpotential of the oxygen evolution reaction (OER). In 1.0 M KOH, U-Co0.90Fe0.10 displayed the lowest overpotential 326 mV at 10 mA cm−2. This study reveals the mechanism and resource upgrading process of SeO32- removal by Co/Fe-MOF and demonstrates that a small amount of Fe doping could improve the performance of OER.