Photocathode-assisted redox flow desalination

Desalination techniques, such as reverse osmosis, distillation, capacitive deionization, and battery desalination, require lots of electrical or thermal energy consumption. Herein, we propose a consumption-free electrochemical desalination method based on a light-driven photocathode with a Pt/CdS/Cu 2 ZnSnS 4 (CZTS)/Mo architecture. Modification of a CdS layer on CZTS can improve the desalination performance due to the formation of inner p-n junction between CdS and CZTS which enhances the separation of the photoexcited carriers without recombination. This photocathode-assisted electrodialysis desalination plays the dual functions of both energy conversion and ion removal with the blocking of ion exchange membranes. The [Fe(CN) 6 ] 3−/4− redox couples are recirculated between the anode and photo-cathode as the electrolyte while the salt streams are fed into the middle compartment. Under light illumination, this architecture produces photo-generated electrons to the redox couples with the conversion of [Fe(CN) 6 ] 3− to [Fe(CN) 6 ] 4− at the positive chamber, causing cation capture in the presence of an ion-exchange membrane. At the same time, [Fe(CN) 6 ] 4− is oxidized at the negative reservoir. The light-driven electrochemical reaction of electrolyte redox couples can result in a continuous desalination process. This work will be significant for consumption-free photoelectrochemical desalination research. A consumption-free electrochemical desalination method is demonstrated to work based on a light-driven photocathode with a Pt/CdS/CZTS/Mo architecture.