Cutting-Edge OER Electrocatalysts for Sustainable Seawater Electrolysis: Progress, Obstacles, and Future Prospects

The oxygen evolution reaction (OER) has a significant influence on the hydrogen evolution reaction (HER) in the electrocatalytic splitting of water/seawater, because of its sluggish reaction kinetics and complex mechanism. Additionally, in the case of seawater, the presence of chloride anions is harmful for the metallic electrocatalysts and their electrode surfaces, leading to oxidation and the generation of environmentally harmful chlorine gas or hypochlorite ion during the oxidation process, decreasing the efficiency for OER and hampering the overall electrolysis process. To tackle this problem, highly potent and advanced OER electrocatalysts needs to be designed for electrolyzing seawater. This paper presents a detailed discussion on the recent progress made in the research and development of OER electrocatalysts for the process of splitting seawater. It comprehensively explores the use of many types of catalysts, such as polymetallic and heterostructure phosphides, layered double hydroxide-based materials, transition-metal oxides, spinel and perovskite metal oxides, and nitride catalysts, in the process of seawater electrolysis. A summary of the overall seawater splitting performances of few recently reported catalysts falling in the above categories has been provided. An overview of the current state of affairs that includes the expenses, synthesis difficulties, activities, and electrocatalyst stability has been provided in order to aid in a more accurate assessment. The DFT calculations and in situ characterization methods that help in catalyst development are highlighted extensively in this article. Furthermore, a number of requirements that could come up during the electrochemical conversions have been covered, including high conductivity, corrosion resistance, and the ability to avoid aside oxidation and reduction processes. Additionally, the superhydrophilic and superaerophobic properties of the electrode have been incorporated. This particular property enhances the electrode's interaction with the electrolyte, increases mass transfer efficiency, and speeds up the removal of O2 bubbles during the electrocatalytic OER. Compared to freshwater electrolysis, a variety of challenges have been hampering the practical application of seawater electrolysis (SWE). This paper provides a thorough summary of all relevant data required to generate an effective and active catalyst for SWE.