Lignin-Supported Heterogeneous Photocatalyst for the Direct Generation of H 2 O 2 from Seawater.

The development of smart and sustainable photocatalysts is in high priority for the synthesis of H 2 O 2 because the global demand for H 2 O 2 is sharply rising. Currently, the global market share for H 2 O 2 is around 4 billion US$ and is expected to grow by about 5.2 billion US$ by 2026. Traditional synthesis of H 2 O 2 via the anthraquinone method is associated with the generation of substantial chemical waste as well as the requirement of a high energy input. In this respect, the oxidative transformation of pure water is a sustainable solution to meet the global demand. In fact, several photocatalysts have been developed to achieve this chemistry. However, 97% of the water on our planet is seawater, and it contains 3.0-5.0% of salts. The presence of salts in water deactivates the existing photocatalysts, and therefore, the existing photocatalysts have rarely shown reactivity toward seawater. Considering this, a sustainable heterogeneous photocatalyst, derived from hydrolysis lignin, has been developed, showing an excellent reactivity toward generating H 2 O 2 directly from seawater under air. In fact, in the presence of this catalyst, we have been able to achieve 4085 μM of H 2 O 2 . Expediently, the catalyst has shown longer durability and can be recycled more than five times to generate H 2 O 2 from seawater. Finally, full characterizations of this smart photocatalyst and a detailed mechanism have been proposed on the basis of the experimental evidence and multiscale/level calculations.