Modulating zero charge potential of Zn-doped N, P-containing carbon electrodes for efficient copper ion electrosorption

Nitrogen/phosphorus (N/P) doped carbon materials exhibit enhanced electro adsorption capability in capacitive deionization (CDI) applications. However, the incorporation of N/P atoms may introduce electron-withdrawing groups to the electrode surface, impacting the potential of zero charge (E_PZC) and thereby influencing its electro adsorption efficiency. This research explores the modulation of electrode surface charge by varying the N/P doping composition. Specifically, it presents a Zn and N/P co-doped carbon material employed as the CDI cathode, showcasing selective adsorption of Cu²⁺ ions. Under a voltage of 1.2 V, the adsorption capacity achieves 250 mg/g in a 500 mg/L Cu²⁺ ion solution. Furthermore, it demonstrates outstanding cycling stability, maintaining an adsorption capacity of 233 mg/g even after 21 cycles. This investigation introduces an innovative approach for E_PZC adjustment and offers a fresh theoretical framework for fabricating high-performance CDI electrodes.