Thermal Effects on Osmotic Power Generation in Graphene Oxide Nanochannel Membranes

In this study, we conducted both experimental and numerical investigations to elucidate the thermal effects on osmotic power generation in graphene oxide (GO) nanochannel membranes. The experimental results reveal that a higher power density is achieved when the temperature gradient is applied in the direction opposite to the salinity gradient, whereas a lower power density is observed when both gradients are aligned. Based on the theory of ionic thermoelectricity in nanoconfined electrolytes, we attribute this behavior to the temperature-dependent ion electrophoretic mobility (TDIEM), which plays a critical role in non-isothermal osmotic power generation. When the temperature gradient opposes the salinity gradient, the thermally induced ionic current arising from TDIEM aligns with the diffusion current, thereby enhancing the short-circuit current and, consequently, increasing the maximum power density. This experimentally observed trend is qualitatively consistent with the numerical predictions obtained from a non-isothermal Poisson–Nernst–Planck (PNP) model. These findings provide important insights into the design and optimization of non-isothermal osmotic energy harvesting systems.