(511g) Producing Hydrogen from Simulated Seawater Using a Novel Sonochemical Reactor and Titanium Dioxide Catalyst

Green hydrogen from seawater is highly desirable as it is the most abundant source of water. Yet achieving green hydrogen directly from such a source using conventional methods is challenged by the impurities found within seawater that impede and ultimately halt the production of hydrogen. Sonochemistry may provide an alternative path towards the production of green hydrogen from seawater.

Sonochemistry is the use of high frequency pressure waves (ultrasound) to facilitate or enable chemical reactions. It primarily uses cavitation to enact chemical effects within the liquid. Cavitation is the formation and subsequent behaviour of gas-vapour bubbles in solution owing to the large pressure changes in the liquid. These bubbles may violently collapse to produce extreme temperatures temporarily and locally. These temperatures can exceed 5000°C and is known to partially split water to hydroxyl and hydrogen radicals. These radicals may recombine to form hydrogen peroxide and hydrogen gas. Indeed, previous work has demonstrated that hydrogen can be produced from simulated seawater using conventional sonochemical reactors. Yet, these reactors are difficult to scale up and are not energy efficient, reducing the potential benefits of sonochemistry for green hydrogen.

Recently, we developed a novel sonochemical reactor. This reactor using cylindrically converging acoustic waves to greatly amplify the pressure amplitudes within the reactor. It also separates the ultrasound transducer from the reactor vessel, preventing the challenges presented by impurities within the seawater. This intensification of acoustic fields also concentrates cavitation and thus the chemical effects. The work presented here demonstrates the potential of using sonochemistry in combination with titanium dioxide catalysts to form hydrogen from simulated seawater. Specifically, we explore the performance of our reactor under different acoustic conditions to optimise hydrogen yield and production rate. We show that our novel reactor design in combination with catalysts is more energy efficient than previous work.