Double-layer humidity to electricity converter based on oxide powders with opposite ionic conductivity for operation without humidity gradient

This article inform about creating a new variant of humidity to electricity converter (HEC) based on different types of zirconia powders – double-layer HEC. The powders that were used in the work differ in chemical composition (Y- and Mg-stabilized ZrO₂) and surface properties (positive and negative charged) and allow realizing the charge separation of moving water ions and generate the electric power under ion gradient diffusion in the presence of water molecules in the atmosphere without humidity gradient. Due to the opposite ionic conductivity with respect to protons and OH groups, this HEC separate charges more efficiently compared with converters operating only by the streaming potential mechanism under humidity gradient conditions. The resulting humidity to electricity converter can generate, for a long time, an open-circuit voltage of up to 120 mV combined with a power density of 2.2 μW on the optimal load resistance. Reducing the internal resistance of the converter by adding graphite particles to both parts of the converter and creating a network of percolation paths for water ions and electrons made it possible to increase the open-circuit voltage to 0.16 V, reduce the internal resistance to 120 Ohm and increase the power to 56 μW (4.7 μW/cm²).