Electrodeposition nanofabrication of graphene oxide/polypyrrole electrodes with high hybrid specific capacitance for enhancing U(VI) electrosorption

The uranium-containing wastewater generated in the nuclear fuel cycle poses a serious threat to the environmental ecosystem, and electrosorption can be an effective method for U(VI) removal. Herein, the electrodeposition nanofabrication of a novel composite electrode (GO/PPy) with high hybrid specific capacitance for U(VI) electrosorption. The results showed that the combination of GO with PPy significantly improved the specific capacitance, conductivity and cycling ability, thereby enhancing U(VI) electrosorption. Among various GO/PPy composites, GO/PPy-0.2 presented the highest specific capacitance, and its electrosorption capacity of U(VI) was also the highest, owing to its high specific capacitance and open interlayer channels for ion storage. The cyclic voltammetry characteristic of GO/PPy-0.2 is characterized by capacitive control, which highlights the contribution of PPy pseudocapacitance to electrosorption. The isotherms and kinetics of U(VI) electrosorption were found to be well-simulated by the Langmuir model and the PFO model, respectively. The maximum U(VI) electrosorption capacity reached 246.5 mg/g at pH 4.0 and 0.9 V. This work provides a feasible strategy for the electrodeposition nanofabrication of high-performance GO/PPy electrodes by incorporating a EDL capacitance material (GO) with a pseudo-capacitance material (PPy) to improve the specific capacitance and stability of the electrodes. Meanwhile, it also provides insights into electrosorption mechanism based on hybrid capacitance (double layer capacitance and pseudo capacitance) and N/O complexation, which was confirmed by XPS and FTIR characterization. Overall, the excellent electrochemical electrosorptive performance of GO/PPy-2 endows its promising application in CDI for efficient separation of U(VI) from radioactive wastewater.