Engineering bimetallic capture sites on hierarchically porous carbon electrode for efficient phosphate electrosorption: multiple active centers and excellent electrochemical properties

Abstract

Excessive phosphate in water bodies has become a major concern because it causes eutrophication and even disrupts the aquatic ecological balance. Electro-assisted adsorption exhibited great potential for wastewater treatment due to its efficient and rapid removal capacity, facile operation, and low cost. The key to electrosorption technology lies in the development of electrode materials. In this work, the bimetallic Ti–La active centers were created on novel hierarchically porous carbon electrode materials (TLPCs) via in situ growth of LaMOF on hierarchical TiO₂ followed by co-pyrolysis treatment. The TLPC2 electrode exhibited an exceptional phosphate removal capacity of 231.56 mg g⁻¹ with a rapid rate at 1.2 V, which is superb in comparison with that of other electrode materials from the literature. Higher correlation coefficients of the pseudo-second-order model demonstrate that the phosphate removal process involves both reaction on the electrode surface and chemisorption. The synergistic contribution of Ti and La not only delivers multiple active centers and plentiful oxygen vacancies but also boosts electrochemical activities. The superior phosphate removal capability can be ascribed to the coupling of electric field, ligand exchange, oxygen vacancy sites consumption, and electrostatic attraction. Moreover, the selectivity, stability, and actual water treatment for phosphate removal were maintained well even under comprehensive conditions. This study illustrates an insight into phosphate electrosorption and promotes the expectation for highly efficient electrode materials.