Challenges of Hydrogen Evolution in Seawater Electrolysis: The Role of Chlorine Evolution

Abstract

The shift towards green hydrogen production is imperative for accomplishing sustainable energy goals, particularly through seawater electrolysis. However, the simultaneous occurrence of the chlorine evolution reaction (CER) poses a substantial challenge by competing with the oxygen evolution reaction at the anode, thereby reducing the catalyst's efficiency and selectivity. This review critically examines the modern strategies for mitigating CER, focusing on the development and application of advanced nanomaterials. The emphasis is on transition metals and their oxides, 2D materials, layered double hydroxide-based electrocatalysts, and core–shell nanostructure-based electrocatalysts, highlighting their electrocatalytic properties, structural advantages, and potential drawbacks. Moreover, this review presents a balanced assessment of their benefits, including improved catalytic activity and stability, and their limitations, such as cost and scalability. Furthermore, this review reports the advantages and disadvantages of the CER, revealing that competing CERs can suppress the HER Faradaic efficiency by 20%–30% in chloride-rich electrolytes (~ 0.5 mol L⁻¹ Cl⁻). The conclusion and future outlook focus on the key findings, highlighting the necessity for continued innovation in material design and engineering. This review aims to guide researchers and industry stakeholders in developing more efficient and sustainable technologies for seawater electrolysis.

Graphical Abstract

Keywords

Chlorine evolution reaction / Green hydrogen production / Sustainable energy / Methodologies / Strategies / Nanomaterials / Catalysis

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