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With the growing global freshwater crisis, seawater desalination has become an essential way to obtain freshwater resources. The flow-electrode-based electrochemical desalination is a promising desalination technology, which possesses the continuous desalting process and an unlimited desalination capacity in theory. Recently the redox couples are emerging as an additive to enhance the salt removal rate and lower the energy consumption. In this review, the flow-electrode based desalination technology is introduced based on carbon flow material and redox couples. The desalting mechanisms, configurations and performance indicators are analyzed and discussed. The impact factors of desalination performance such as the type and dosage of active materials, conductive additives, pretreatment processes, flow-electrode regeneration and operation conditions are further investigated. In the last section, the challenges and prospects are predicted for the future development of flow-electrode desalination system. The review and prospect will stimulate further research progress for the practical application of flow-electrode electrochemical desalination technology. • Flow-electrode electrochemical desalination technologies were summarized. • Desalting mechanisms, configurations & impact factors etc. were analyzed & discussed. • The other applications of device were explored except for desalination. • The challenges and prospects are predicted for the future development. [ABSTRACT FROM AUTHOR]

Typical desalination techniques, such as reverse osmosis, distillation, capacitive deionization, and battery desalination, require lots of electrical or thermal energy consumption. As a new emerging desalination technique, the solar-driven photoelectrochemical desalination (SD-PED) technology by using sustainable solar energy to remove salt ions without any external bias has been developed and caused much attention. The SD-PED technique with dual functions of desalination and photoelectric conversion driven by sunlight has demonstrated that a high initial photocurrent up to 9.5 mA can be obtained in the existing work with 99.95% salt removal rate. However, some limitations are remained such as the fast decline of photocurrent, difficulty in the seawater desalination, the long-term stability of system etc. To better understand this new desalination technique, herein, we comprehensively review and discuss the status of SD-PED system for the first time, including the device configuration, influencing factors and the active involved materials of solar absorbers and redox electrolyte species. Further, the strategies to improve the performance of long-term stability desalination are summarized, such as the configuration connection in series or parallel, the combination of photoanode and photocathode, the photosensitive material with wide solar absorption. At last, the challenge and prospect are further guided for the future development of SD-PED technology, which are expected to realize the commercialization. A new type of electricity-free solar-driven electrochemical desalination technique was proposed very recently which could achieve continuous desalination by circulating the redox flow electrolyte. This review comprehensively describes the recent development of SD-PED technique to determine its advantages and disadvantages with guiding further technology development. Followed by discussion the mechanism, device configuration, solar absorber materials, redox electrolyte species and influencing factors of SD-PED system. Finally, state the challenges, discussions for future work, conclusions and perspectives in the last section. The SD-PED technique is a promising solution to the worldwide energy and water shortage crisis. [Display omitted] • The SD-PED technology was reviewed for the first time. • Development and desalting mechanisms of SD-PED technology was summarized. • The configurations, materials and performance influence factors were analyzed. • The challenges & perspectives are guided for the future development of SD-PED. [ABSTRACT FROM AUTHOR]