Constructing enhanced dual active centers on mesoporous carbon electrode for efficient phosphate removal through capacitive deionization

Capacitive deionization (CDI) emerges as an effective and straightforward strategy for the elimination of phosphate, addressing the need for mitigating water eutrophication. Exploring electrode materials with superior performance takes imperative precedence for technological advancement. Herein, CeO₂-anchored B, N co-doped mesoporous carbon composites (CeBCNx) were constructed through hard template and chemical deposition strategies. The multi-atom customization regulated the interfacial charge distribution and boosted the phosphate affinity and capturing potential. As anticipated, the CeBCN2 electrode exhibited dynamic and saturated removal capacities of 162.29 mg PO₄^3- g⁻¹ and 506.29 mg PO₄^3- g⁻¹ at 1.2 V. More importantly, the electrosorption system demonstrated deep elimination of phosphate from simulated low-concentration water. The removal rates for both 3.2 mg P/L and 6.3 mg P/L feed solutions exceeded 95 % over 240 min, in full compliance with the first-class discharge standard (0.5 mg P/L) in China. Theoretical calculations revealed that the combined effect of the B-N bond and Ce site endows reinforced dual active centers and high-speed electron transfer paths. Electrical double layer capacitance, ligand exchange, and electrostatic attraction were jointly involved in the phosphate removal procedure. This work elucidates the theoretical basis of dual active centers and promotes deep phosphate removal techniques.