Interlayer-expanded 1T-phase MoS2 as a cathode material for enhanced capacitive deionization

Abstract

Molybdenum disulfide (MoS2) is a potential material for capacitive deionization (CDI) electrodes due to its large surface area and theoretical capacitance. However, its low electrical conductivity and limited spacing between layers hinder the improvement of the desalination performance. In our research, we combined phase modulation and interlayer engineering methodologies to create a CDI electrode material made of metallic phase MoS2 with expanded interlayer spacing. The high conductivity of the metallic phase facilitates rapid charge transport, while the expanded interlayer spacing (increased from 6.2 Å to 9.8 Å) promotes effective utilization of active sites and reduces the barriers for ion diffusion. The created electrode showcases a notable specific capacitance (131.1 F g−1 at 10 mV s−1) and an elevated capacitive contribution percentage (81 %). Additionally, it demonstrates a high desalination capacity of 47.1 mg g−1 and a fast desalination rate of 2.4 mg g−1 min−1 in a 200 mg L−1 NaCl solution. Furthermore, our density functional theory (DFT) calculations validate the essential role played by enlarged interlayer spacing in promoting Na+ insertion and accelerating its diffusion kinetics.