ABSTRACT: Nanofluidics has received increasing attention in the field of energy conversion in recent years. Various unique ion transport properties within nanochannels, including selective ion transport, ion current rectification, and ion concentration polarization, have been exploited to develop energy-harvesting devices. The ion transport can be caused by various driving forces, such as external pressure gradients, electrostatic forces, temperature, or concentration gradients. Thus, understanding the transport behavior of electrolyte solution through nanochannels is crucial to increasing the energy-conversion efficiency. Porous anodic alumina (AAO) is characterized by self-assembled straight cylindrical nanopores produced by electrochemical oxidation, making it particularly attractive as a material for nanofluidic platforms., The diameter and length of nanochannels can be varied by choosing optimal synthesis parameters. The pore walls are also available for further functionalisation, which makes it possible to use AAO membranes as fundamental materials for the preparation of various nanocomposites. In this work, ion transport within AAO nanochannels was studied, and the impact of the nanoporous platform structural parameters, the charge of the nanochannels` internal surface, and the type/concentration of the electrolyte on ion behavior in the solution was determined. For the current study, AAO membranes were fabricated using the two-step anodisation method in a 0.3 M sulfuric acid electrolyte. The nanochannels were infiltrated with aqueous electrolytes (NaCl, NaClO4, Na2SO4) in the concentration range from 3·10-5 M to 1 M using the hydrostatic pressure-induced method. The infiltration of nanochannels was controlled by electrochemical impedance spectroscopy (EIS). To determine the stability of AAO membrane in an aqueous electrolyte solution the morphology of the membranes before and after infiltration was examined using scanning electron microscopy (SEM). The dependence of ζ-potential values, determined by pressure-driven ion transport, on the charge of the nanochannel walls and solution pH, was established. Moreover, the changes in the electrolyte solution filtration rate were used to indicate the occurrence of nanoconfinement effects or damaging/degradation processes in AAO pore channels. 

This poster was presented by Dr Irina Oliseveca for the IEEE NAP conference held in Riga, Latvia, between September 8-13, 2024. TRANSLATE is a €3.4 million EU-funded research project that aims to develop a new nanofluidic platform technology to effectively convert waste heat to electricity. This technology has the potential to improve the energy efficiency of many devices and systems, and provide a radically new zero-emission power source. The TRANSLATE project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement number 964251, for the action of 'The Recycling of waste heat through the Application of Nanofluidic ChannelS: Advances in the Conversion of Thermal to Electrical energy'. More information can be be found on the TRANSLATE project website: https://translate-energy.eu/