Some people feel the rain. Others just get wet. - Bob Marley -

Under ambient conditions, all exposed surfaces are covered by a thin layer of adsorbed water, inherently modifying the electrochemical environment. Ferroelectric materials, especially, strongly interact with the polar water molecules, which can influence switching dynamics and the shape, size, and stability of the resulting domains, as well as modulating defect-mediated electrical transport at domain walls, while the water itself can condense in a polarisation-selective manner on the surface.

Here, we present our local studies of the interaction between water and ferroelectric materials, carried out by piezorespose force microcopy, electrostatic force microscopy, and Kelvin probe force microscopy imaging in Pb(Zr0.2Ti0.8)O3 thin films. Our studies address the influence of surface water on polarisation switching dynamics, and the role of polarisation orientation as well as switching/charging history on water adsorption and surface charge dissipation at varying relative humidities at room temperature. We also investigate the growth of ice-like water layers at low temperature and high humidity on ferroelectric thin films, demonstrating a polarisation-dependent control over the water layers at submicron scales. These “nanofluidics” could potentially provide a useful control in catalysis applications. Finally, we look at the role of relative humidity on the polarisation-dependent asymmetrical nanotribology induced in ferroelectrics as a result of high strain gradients under a scanning probe microscope tip.

Microfiltration (MF) membranes play a pivotal role in recycling water from food industry wastewater, but their efficiency is hampered by membrane fouling—a buildup of impurities that diminishes permeability.
Ceramic membranes (CMs) surpass polymeric counterparts in durability and lifespan, despite their higher cost. To gain their full potential, enhancing the antifouling performance of CMs is crucial.
Among CMs, self-cleaning piezoelectric technology stands out, demonstrating promising antifouling/defouling capabilities. The SELWA project, funded by NextGenerationEU - European Union, focuses on developing porous lead-free piezoelectric ceramics (BCTZ system) for microfiltration of wastewater. This work presents initial findings on the intricate processes involved, correlating them with microstructure and ferroelectric properties. It explores challenges in transitioning from bulk to porous structures, emphasizing the importance of ferroelectric and surface properties in membrane devices.

Wastewater remediation by advanced oxidation processing based on pyrocatalysis is an emerging topic in recent years. This technique utilizes the pyroelectric effect of crystals with a spontaneous polarization which varies in response to temperature changes. Under thermal cycling, respective variations of the polarization magnitude occur and polarization charges on the pyroelectric crystal surface build up. Although these polarization charges are accompanied by compensation charges at equilibrium, transient net charges can initiate redox reactions. Thus, pyroelectrically generated reactive oxygen species (ROS) such as OH radicals can convert organic micropollutants into nontoxic degradation products. The basic prerequisite for the catalytic process is cyclic and moderate temperature fluctuation which can be supported e.g., by thermal waste energy or solar energy.
Therefore, the pyrocatalytic water treatment has the potential to be applied in developing areas as well as for industry plants´ waste waters. The key to such water remediation reactors is the catalytic efficiency of the pyroelectric material.
Although several studies explored the potential of new pyrocatalytic materials to degrade harmful organic water pollutants, the role of important material properties is still unclear. In this contribution, we investigate the impact of agitator ball milling performed on BaTiO3 based materials that were synthesized by oxide reaction route on their catalytic activity. Results from experiments of pyrocatalytic oxidation of the dichlorofluorescein redox assay (DCHF to DCF) are evaluated with respect to the powder´s specific surface area; further factors that enhance pyrocatalytic activity are discussed. The influence of the synthesis route is considered as well, by including BaTiO3 powder from bottom-up synthesis into the evaluation.

Piezoelectric materials are crucial in modern applications like telecommunications, automotive, electronics, and aerospace. Recently, interest has grown in their use in liquid environments for diverse applications, including biomedical engineering, purification systems, electrocatalysis, fluid characterizations, and micro/nano electromechanical systems (MEMS/NEMS). Despite their significance, questions persist about characterizing and evaluating their performance in liquid media, particularly in understanding their interaction with surrounding ionic species under mechanical stress. This study introduces a novel experimental setup to characterize piezoelectric materials in liquid environments through electrokinetic measurements. Focusing on lead zirconate titanate (PZT) and barium titanate (BT), polarized piezoelectric samples, the research explores the correlation between applied mechanical stress and the resulting electrokinetic responses. The study demonstrates that stress variations on piezoelectric samples closely influence their electrokinetic responses in liquid media. The continuous streaming potential measurement reveals that the electrokinetic response follows the stress profile applied to the piezoelectric sample. In contrast, a non-piezoelectric material (alumina) shows almost no changes in electrokinetic properties under similar stress conditions. Finite element modeling is also employed to analyze the electric responses of the piezoelectric samples as the applied mechanical stress varies.