A review on photocatalytic seawater splitting with efficient and selective catalysts for hydrogen evolution reaction

The rising global demand for clean and renewable energy has spurred interest in innovative technologies capable of addressing both energy production and environmental challenges. Among these, photocatalytic seawater splitting has emerged as a highly promising approach for generating hydrogen, a clean fuel, by harnessing sunlight. Unlike traditional water-splitting techniques that depend on freshwater resources, seawater splitting offers a sustainable alternative by utilizing the vast and readily available oceanic reserves. This process leverages advanced photocatalytic materials, such as metal oxides (e.g., TiO₂, ZnO), perovskites, and 2D materials like graphitic carbon nitride (g-C₃N₄), to enhance the efficiency of the hydrogen evolution reaction (HER). This review provides a comprehensive analysis of the latest advancements in photocatalytic seawater splitting, focusing on catalyst design, performance optimization, and overcoming key challenges such as corrosion, photocatalyst stability, and the detrimental effects of seawater components, including chloride ions and metal cations, on hydrogen production. Special attention is given to the role of novel materials, such as nanosheet arrays, metal-organic frameworks (MOFs), and defect-engineered catalysts, in improving charge separation, reducing recombination rates, and enhancing light absorption under solar irradiation. Furthermore, the review addresses the impact of seawater composition, including the presence of ions such as Na⁺, Mg²⁺, and Ca²⁺, on the photocatalytic process, and discusses strategies to mitigate undesirable side reactions, such as chlorine evolution. The commercial potential of photocatalytic seawater splitting is also considered, highlighting its scalability and integration into renewable energy infrastructures to produce hydrogen as a viable alternative to fossil fuels.