Nitrogen-doped carbon aerogel framework with in situ encapsulated ZrO2 nanoparticles as pseudocapacitive anode for phosphorus uptake

Phosphorus reduction is crucial for controlling eutrophication and protecting the aquatic environment. Nonetheless, traditional methods suffer from secondary pollution and high costs. Capacitive deionization (CDI) is a novel electrochemical approach for phosphorus removal, which is low-cost and environmentally friendly. Its performance is highly correlated with the electrode material. Herein, a novel nitrogen-doped carbon aerogel framework encapsulated with ZrO2 nanoparticles (ZrNC) was rationally fabricated and employed as an anode for phosphorus removal. The experimental results revealed that the N site and ZrO2 could enhance the physicochemical properties, electrochemical activity, and additional pseudocapacitive contribution, thus raising the phosphorus removal capacity. The optimal ZrNC-3 electrode demonstrated superior phosphorus capture (18.26 mg P/g), low energy consumption at 1.2 V (0.0256 kWh/m3 and 4.159 kWh/kg), outstanding phosphorus selectivity, and excellent stability. Mechanism investigation suggested phosphorus can form mono- or bi-dentate inner-sphere complexes (Zr–O–P) by ligand exchange with ZrO2 sites under an electric field and combined with unsaturated Zr sites and N species by electrostatic attraction. This study presents a promising conception for designing and applying metal oxide/carbon complexes in selective phosphorus uptake electrodes.