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Abstract In this work, we report the use of pseudocapacitive RuO 2 in a porous carbon-based substrate as a composite electrode for high-performance capacitive deionization (CDI). RuO 2 was electrodeposited onto inexpensive activated carbon (AC) via cyclic voltammetry to optimize the composite electrode (denoted as RuO 2 (20)-AC) fabrication. The electrochemical measurements indicate that the composite electrode with a specific surface area of 576 m2/g and hydrophilicity yields an improved specific capacitance and good cycling stability. The notably enhanced performance is attributed to the presence of RuO 2 , which allows rapid Faradaic charge-transfer reactions as well as pseudocapacitive charge storage. These results confirm that incorporating RuO 2 onto an AC electrode effectively reduces the electrical resistance and enhances the charge efficiency. Furthermore, batch-mode CDI experiments were conducted at 1.2 V in a 5 mM NaCl solution. As evidenced, the RuO 2 (20)-AC composite has a promising salt adsorption capacity of 11.26 mg/g, which is 3.7-fold higher than that of pristine AC. Therefore, using the RuO 2 (20)-AC composite as the cathode, an enhanced desalination performance can be achieved through a mixed capacitive-Faradaic process, resulting from two removal mechanisms of capacitive electrosorption and pseudocapacitive redox reactions. This work provides an efficient strategy to utilize RuO 2 on porous carbon-based substrates to improve CDI performance. Highlights • RuO 2 /activated carbon composite electrodes were prepared for CDI. • Electrodeposited RuO 2 showed good pseudocapacitive charge storage. • The metallic conductivity of RuO 2 ensures rapid ion transport. • The composite had a superior salt electrosorption capacity. • The combination of capacitive electrosorption and Faradaic reactions enhanced the CDI performance. [ABSTRACT FROM AUTHOR]

• Electrochemical separations can play a role in improving PFAS removal efficiency. • Electrosorption using functionalized carbon materials offers tunable selectivity. • Electrooxidation and plasma-based methods are promising electrically-driven methods for PFAS destruction. • Coupling of separation and reaction through electrochemical approaches can lead to process intensification in PFAS remediation. Organic anthropogenic pollutants such as per- and polyfluorinated alkyl substances (PFAS) present a severe threat to bodies of water and neighboring ecosystems, due to their toxicity and recalcitrance to current treatment methods. PFAS have highly stable carbon-fluorine bonds that contribute to the persistence of these compounds in the environment. Conventional separation methods based on membranes or adsorption materials can often be inefficient at targeting PFAS, or require significant energy or chemical consumption for regeneration.. Electrochemical approaches offer a sustainable and potentially energy-efficient solution to PFAS capture and degradation, with rapid development of new electrode materials and electrochemically-driven processes for the separation and reaction of these compounds. Here, we review electrochemical approaches for PFAS removal and degradation, including electrosorption and electrochemical oxidation/reduction processes. In particular, we discuss investigations using porous carbon electrodes and functional polymers for PFAS electrosorption, as well as electrodes used for PFAS defluorination such as boron-doped diamond. Finally, we present a perspective on emerging topics in electrochemical PFAS remediation, such as the integration of electrochemical reaction and separations, and the urgent need for remediation studies of short-chain PFAS. [ABSTRACT FROM AUTHOR]