Endowing turbostratically porous carbon with rich edge nitrogen active sites for efficient capacitive removal of phosphate

Abstract

The mitigation of phosphate in water is a pivotal concern for the prevention of eutrophication and enhancement of water quality. Capacitance deionization (CDI) technique possesses the merits of high removal efficacy, facile operation, and environmental friendliness, rendering it a promising strategy for phosphate elimination. Herein, the nitrogen-rich laminar porous carbon composites (NTPCs) prepared by direct pyrolysis of supermolecular precursor were utilized as phosphate capture electrodes. The resulting NTPC800 features a high nitrogen content turbostratically amorphous carbon framework, which facilitates efficient ion diffusion pathways and electron transfer. The abundant presence of edge nitrogen (pyridine and pyrrole nitrogen) optimizes the electronic structure of the carbon system and provides more active sites, thus leading to the boosted electrochemical activity and dephosphorization efficiency. Consequently, NTPC800 demonstrates a rapid phosphate removal capacity, achieving 73.51 mg g−1 within a mere 10 min at 1.2 V condition, which is nearly 6 times more efficient than that of the commercial activated carbon electrode. Moreover, it exhibited consistent phosphate removal efficiency across various pH ranges, coexisting ion interferences, and cyclic stability assessments. This study provides theoretical support for the utilization of edge nitrogen decorated carbonaceous electrodes to enhance charge transfer and provide additional active sites for efficient capacitive dephosphorization.