Identifying Sweet Spots for Redox Reactions in Electrochemical Advanced Oxidation and Reduction Processes for Pollutant Degradation and Resource Recovery

There is a growing interest in transforming conventional infrastructure-heavy wastewater treatment processes into small-scale, modular, decentralized, electrified, and consequently resilient processes toward fit-for-purpose applications. Electrochemical wastewater treatment systems have emerged as one of the most promising candidates. However, electrochemical methods intended for wastewater treatment still need to overcome some unique technological hurdles compared to electrochemical systems operated under well-defined and often uniform conditions, such as those used in batteries and fuel cells. Developing active, selective, and stable electrode materials that can energy-efficiently drive desired anodic oxidation and cathodic reduction reactions under a complex wastewater matrix has been challenging despite extensive research. An equally critical subject is developing electrochemical systems that are energy- and cost-competitive with existing alternative technologies that achieve the same treatment goal. Finally, a fundamental understanding of electrochemical phenomena that are either advantageous or detrimental to water treatment applications must be further developed and leveraged through advanced characterization techniques and computational simulations. This critical review aims to identify future opportunities and prospects for electrochemical wastewater treatment for pollutant degradation and resource recovery. We discuss various materials, operating conditions, and system design strategies to enhance the catalytic performance and energy efficiency of the desired reactions. Furthermore, we extend the discussion to parasitic reactions involving various cations, anions, and organics that are detrimental to water treatment goals.