Shedding light on the photocatalytic hydrogen generation from seawater using CdS

The current energy crisis, in addition to the severe drought our planet is suffering, had led to the search for new alternatives to obtain green and sustainable fuel sources. Green hydrogen as an energy vector is one of the most promising possibilities. In this context, emerging technologies, such as photocatalysis, that can be driven by solar light, become especially challenging when using natural seawater (NSW) directly, avoiding previous purification steps. The exploitation of this endless resource is key to tackle the climate and energy emergency, although it faces questions derived from the presence of dissolved salts at significant concentrations. So far, some reports attribute to the latter the catalyst deactivation and loss of performance, whereas other authors have compared the results obtained with NSW and synthetic seawater and have reported higher rates of hydrogen generation with NSW. To solve this controversy, further research is needed to assess both the viability of the photocatalytic hydrogen generation from NSW and the conditions for the optimum process performance. Within this context, this study has evaluated two easy to purchase photocatalysts, TiO2 as benchmark, and CdS, in a concentration range from 50 to 150 mg L-1. Different sacrificial agents are used depending on the catalyst, 20% CH3OH for TiO2 and 0 to 0.1 mol L-1 Na2S/Na2SO3 range for CdS. The experiments performed in batch mode gave promising results and shed new light on the positive influence of the buffer capacity of NSW, providing information about the mechanisms that take place during the process. Furthermore, this study fosters the advancement of hydrogen production technologies based on abundant and inexpensive raw materials.