Fabrication of an efficient hierarchical mesoporous 2D-MoS2/CNT/polypyrrole based composite electrodes for competitive and selective U6+ removal using capacitive deionization: Mechanistic evaluation through cyclic voltammetry

In this work, efficient and selective carbonaceous electrode materials based on hierarchical mesoporous functionalized carbon nanotubes, 2D-MoS2 nansheets electrodeposited with variable content of polypyrrole (PPy) were prepared. The simple etching reaction between HNO3 and carbon nanotubes did not only modify the surface but also improved its hydrophilicity. The annealing of carbon nanotubes and electrodeposition of polypyrrole increased the mesopore volume to total volume ratio (Vmeso/Vt) from 0.42 to 0.86. The composite materials were characterized wisely using different characterization techniques and employed for efficient U6+ electro-assisted sorption through capacitive deionization. Electrode material with polypyrrole content (0.3 M) exhibited good specific capacitance Csp (100.2 F/g), improved Vmeso (0.61 cm3/g), superb Vmeso/Vt ratio (0.86) and large specific surface area SBET (149.7 m2/g). The stated electrode showed fast sorption kinetics (teq=30 min), admirable selectivity and exhibited the experimental sorption capacity of 274.50 mg/g at -0.90 V. Electrochemical impendence spectroscopic study revealed that the resulting material exhibited relatively small charge transfer resistance (1.19 Ωcm2), minute electrolytic resistance (0.91 Ωcm2) and large double layer constant phase element (0.0368 S sn/ cm2). These significant characteristics promoted U6+ ions diffusion inside the hierarchical porous electrode surface for better performance of electrosorption process. This new class of hierarchical mesoporous composite electrodes may be used as potential supercapacitor materials not only for removal of uranium but also for other potent desalination applications.