Remarkable phosphate electrosorption/desorption by bimetallic MOF-derived hierarchically porous carbon electrode: In-situ creation of multiple active centers and boosting electrochemical activities

Elimination of phosphate is essential to control eutrophication and improve water quality. Nevertheless, the removal capacity of dephosphorization agents in conventional methods is far from satisfactory. Herein, we proposed an electro-assisted adsorption method and fabricated a novel bimetallic Zr-Al metal organic framework (MOF) derived hierarchically porous carbon (ZAMC-13) electrode for efficient phosphate electrosorption. The results of systematic experimental indicated that the synergistic contribution of Zr and Al can boost the electrochemical activities and oxygen vacancies, thus resulting in an increased reaction rate and removal capacity. The ZAMC-13 electrode, as expected, demonstrated a remarkable phosphate electrosorption capacity of 539.85 mg/g at 1 V, with an exceptional regeneration performance of 90.59% after 20 consecutive cycles using a reverse voltage. The electrosorption behavior was further revealed using kinetic and isotherm models. Besides, the phosphate electrosorption mechanisms, which were primarily dominated by ligand exchange, electrostatic attraction, oxygen vacancies consumption, and electric field, were elucidated. Furthermore, the energy consumption and operating cost for electro-assisted phosphate removal are as low as 0.0108 kWh/kg P and 0.020 $/m3, respectively. This work demonstrates a deep understanding and promotes a new level of electro-assisted phosphate adsorption.