Retrievable Hierarchically Porous Ferroelectric Ceramics for “Greening” the Piezo-Catalysis Process

Powder-based piezo-catalysis, as an effective approach to degrade wastewater and produce hydrogen from water splitting, has been widely used in the field of energy conservation and pollution reduction. However, these hard-to-recycle powders pose a challenge of secondary pollution in the environment. As a result, this paper provides an alternative strategy based on the manufacture of porous ceramics as a green chemistry approach to replace ferroelectric powders currently used in traditional piezo-catalysis. The piezo-catalytic properties of Ba_0.75Sr_0.25TiO₃ (BST) ceramics prepared using freeze casting and direct ink writing techniques are investigated in detail. The positive effect of introducing micro- and macro-pores is explored and discovered, where a BST ceramic with hierarchical pore channels is prepared by a combination of direct ink writing and freeze casting and exhibts the highest first-order kinetic rate constant per mass of catalysts, k, of up to 2.91 min⁻¹ kg⁻¹ compared to bulk BST ceramics. This study therefore provides the first report for the benefits of hierarchical porous ferroelectric ceramics used in water splitting, with an average H₂ production rate reaching 848.88 nmol g⁻¹ h⁻¹.