High-performance pseudocapacitive removal of cadmium via synergistic valence conversion in perovskite-type FeMnO3

Cadmium pollution is a serious threat for the global drink water and natural environment. Herein, a poly-pyrrole coated dual-metal perovskite-type oxide FeMnO3 (PFMO@PPy) was developed firstly as pseudocapacitive cathode for the reversible capture and release of cadmium ions by asymmetry pseudocapacitive deionization (APCDI) technology, extending the library of CDI electrodes. Our work highlighted several points: (i) PFMO@PPy achieved a maximum Cd-removal capacity of 144.6 mg g-1, and maintained the retention rate of 93.4% after 15-cycle CDI process for up to 150 h, far beyond other previous work. (ii) PFMO@PPy showed the superior removal ratio (~90%) under different real water environments such as tap water, lake water and the groundwater. (iii) The superior Cd(II) electrosorption and desorption behavior is ascribed to the reversible synergistic valence conversion (Fe3+/Fe0 and Mn3+/Mn2+), which is confirmed by ex-situ XPS measurement and electrochemical tests. (iv) DFT calculations confirmed the synergistic effect from Mn and Fe elements in perovskite-type bimetallic oxide FeMnO3. This study paves a new way for promising future applications of perovskite-type oxides containing dual Faradic redox-activity for wastewater treatment and environmental remediation.