PH-temperature coupled regulation for promoted nanofluidic osmotic energy conversion

Abstract

pH and temperature regulation effectively enhance the performance of nanofluidic osmotic energy conversion, but their combination is rarely studied numerically, causing unclear influences on selective ion transport and power generation. In this study, a model considering the coupled influence of pH and temperature on interfacial reactions is established for osmotic energy conversion. The increases in pH and temperature synergistically promote the interfacial deprotonation reaction and increase the surface charge density. Accordingly, the dimensionless number called the electrical double layer intensity is defined to describe the neutral deviation of the electrical double layer, which is obviously enhanced by raising the pH and temperature at low pH. Moreover, according to the pH value and ion selectivity, the energy conversion performance under temperature regulation is divided into the interface-dominant zone and the solution-dominant zone. The elevated temperature improves the osmotic energy conversion mainly by improving the interface property at a low pH but mainly by altering the solution properties at a high pH. Finally, fluid convection plays an important role at a relatively high pH value. This work provides a comprehensive understanding of the pH and temperature coupled regulation mechanisms and points out the design route for high output power.