High Efficiency Water Splitting using Ultrasound Coupled to a BaTiO₃ Nanofluid

To date, a number of studies have reported the use of vibrations coupled to ferroelectric materials for water splitting. However, producing a stable particle suspension for high efficiency and long-term stability remains a challenge. Here, the first report of the production of a nanofluidic BaTiO₃ suspension containing a mixture of cubic and tetragonal phases that splits water under ultrasound is provided. The BaTiO₃ particle size reduces from approximately 400 nm to approximately 150 nm during the application of ultrasound and the fine-scale nature of the particulates leads to the formation of a stable nanofluid consisting of BaTiO₃ particles suspended as a nanofluid. Long-term testing demonstrates repeatable H₂ evolution over 4 days with a continuous 24 h period of stable catalysis. A maximum rate of H₂ evolution is found to be 270 mmol h^-1 g^-1 for a loading of 5 mg l^-1 of BaTiO₃ in 10% MeOH/H₂ O. This work indicates the potential of harnessing vibrations for water splitting in functional materials and is the first demonstration of exploiting a ferroelectric nanofluid for stable water splitting, which leads to the highest efficiency of piezoelectrically driven water splitting reported to date.