Thermal-enhanced nanofluidic osmotic energy conversion with the interfacial photothermal method

Nanofluidic osmotic energy conversion is widely considered a promising technology that converts sustainable salinity-gradient energy. Current studies on temperature regulation require extra electrical consumption to raise the solution temperature, causing the deterioration of the net power generation. In this study, a thermal-enhanced nanofluidic osmotic energy conversion with photothermal conversion structure (PCS-TOEC) integrated device is proposed to utilize sustainable solar energy as the heat source. This device is a reformation by adding photothermal conversion structure (PCS) into a salinity gradient utilization component. PCS is composed of a high solar-absorption cupric oxide film and a high thermal-conductive silicon carbide porous foam, and it can efficiently convert solar energy into solution heat. In addition, PCS can promote bulk heating at a high rate. The experiment shows that the solution temperature is raised from 25 ℃ to 68 ℃ after 240 min under one sun illumination, and the output power density achieves 8.6 W/m² with 0.5 M/0.01 M NaCl solution, exhibiting a 188 % increase compared to that at room temperature. The increased bulk solution temperature under the photothermal effect can improve the ion diffusion coefficient and electrolyte convection, as well as reduce the electrolyte viscosity, resulting in the enhancement of the associated ion flux. The underlying mechanism of thermally enhanced osmotic power is primarily attributed to the elevated ion flux at increased bulk solution temperatures. Finally, the environmental adaptability of this device is verified over a wide range of concentration gradients (from 10-fold to 100-fold) and pH (from 4 to 10) conditions. In this work, a sustainable solution that enhances osmotic power generation is provided, and a novel method that achieves hybrid renewable energy cooperative utilization is developed.