Impact of harmful ions in seawater on electrolysis catalysts: challenges and mitigation strategies

Direct seawater electrolysis presents a promising solution to address both freshwater scarcity and the growing demand for green hydrogen in regions abundant in renewable energy. This study first investigates the electrochemical mechanisms of seawater electrolysis, decomposing the process into cathodic and anodic reactions. It then reviews the impact of seawater's complex ionic composition on electrocatalyst performance, focusing on activity, selectivity, and stability. The challenges posed by anionic interference from Cl- and Br-, and cationic interference from Mg2+ and Ca2+, are discussed, along with effective mitigation strategies. Solutions to mitigate the impact of anions on the anode, such as heterojunction engineering, nanostructure design and constructing anti-corrosion layers, are proposed. Anodic small molecule oxidation is employed as an alternative to the oxygen evolution reaction (OER) to decrease the overall energy consumption. For the cationic interference on the cathode, strategies like maintaining the hydrophobicity of the electrode and electrolysis cell design are suggested. Finally, this review summarizes the remaining challenges, presents feasible solutions, and highlights key considerations for scaling up seawater electrolysis for commercial hydrogen production. This review provides valuable insights to accelerate the development of sustainable, large-scale seawater hydrogen production technologies.