Enhanced light-driven ion transport via graphene oxide composite membranes for ionic power harvesting

In nature, biological active ion transport plays a pivotal role in efficient energy harvesting. However, replicating this process in artificial systems to achieve comparable performance remains a significant challenge. Here, we demonstrate a substantial enhancement in light-driven active ion transport by intercalating one-dimensional (1D) carboxymethyl cellulose nanofibers (CNFs) into the layers of aligned two-dimensional (2D) graphene oxide (GO) nanosheets, forming GO composite membranes (GOCMs). The introduction of CNFs increases the interlayer spacing and modifies both the surface and the confined channel chemistry of the membrane. Under visible light illumination, the local electric potential and ion conductivity are significantly enhanced due to the optimal channel height, improved ion selectivity, and accelerated electron consumption. These improvements enable high-efficiency ionic power harnessing in equilibrium electrolyte solutions. Directional cationic transport from the illuminated to the unilluminated side was observed, with the GOCM containing 30 wt% CNFs achieving a peak photocurrent of 2.2 mu A cm-2, which is more than four times higher than that of a pure GO membrane (GOM). As a result of the enhanced light-driven ion transport, the system achieved a high-power density of 0.15 mW m-2 in equilibrium electrolyte solutions. This innovative strategy, based on photoinduced active ion transport, offers a novel approach for biomimetic energy harvesting.