Stable and efficient self-sustained photoelectrochemical desalination based on CdS QDs/BiVO4 heterostructure

Abstract

Herein, we propose a stable and efficient photo-driven electrochemical desalination technique without any external bias. The whole desalination process is driven by CdS quantum dots (QDs) sensitized BiVO4 photoanode, where I-/I3- redox couples are recirculated as the electrolyte. Two salt streams are sandwiched between the photoanode and cathode. The salt ions in desalted stream are continuously extracted by the redox reaction of I-/I3- electrolyte at their respective electrode chambers. The initial photocurrent of 2.58 mA/cm2 can be obtained in the present photoanode-assisted desalination device, which is much greater than the previous reported results. Besides, the electrical current of the photo-electricity conversion system is extremely stable in the current system. Within the four batch cycles, the variation of salt removal rate is as low as 2.3 μg/(cm2•min) without significant decay. The photoanode-electrolyte interface, charge separation and transportation are further investigated by photoluminescence, electrochemical impedance spectroscopy and Mott-Schottky analysis. The promising desalination performance can be attributed to the synergistic effect of CdS QDs and BiVO4 heterojunction which is applied in the field of solar-driven desalination for the first time. This work is significant for the design of high light-absorbing heterojunction photocatalysts for the dual functions of energy production and water desalination.