Nanofluidic Photoionic Membranes for Light Energy Harvesting and Conversion

Abstract

Light energy harvesting and conversion are essential for addressing the global energy crisis. Inspired by the photoinduced energy conversion processes in biological systems, artificial nanofluidic membranes were developed with photoresponsive properties as ion transport media to harvest light, undergo various responses (cleavage, isomerization, and excitation), and ultimately build potential energy (chemical or electric) and ion-transport induced electron transfer (the origin of electricity). This review summarizes recent advances in photoionic membranes for solar-electric energy conversion, including photoactive materials, fabrication of membranes, and analysis of their energy conversion performance combined with some biomimetic features, e.g., anticoncentration gradient ion pumping and alternating ion transport. Current progress, challenges, and insights for future development are also discussed at the end.

Ion transport in nanofluidics under external fields

“…In addition to 2D nanosheet-based nanofluidic systems, hybrid nanofluidic membranes with different structures have also been conventionally used in ion pump systems. 263 Yang and co-workers fabricated a Janus microporous membrane by combining reduced graphene oxide (rGO) and a conjugated microporous polymer (CMP) for active ion transport and the direction of the ion flow can be controlled by manipulating the junction architecture. 38 Moreover, the MOF membrane enable precise and robust optoelectronic ion transport modulation, driving uphill cation transport with light, which results from the Schottky barrier formed upon decoration with platinum nanoparticles that facilitated charge separation.…”

Unipolar Ionic Diode Nanofluidic Membranes Enabled by Stepped Mesochannels for Enhanced Salinity Gradient Energy Harvesting

“…Over the past few decades, advances in nanofabrication and synthesis have greatly facilitated the research on nanofluidics, − which can manipulate ion flows at length scales of <100 nm. In nanofluidic ion channels, dominant intermolecular forces, such as steric interactions, hydration, van der Waals, and electrostatic interactions, endow them with unique selective mass transport capabilities. − These properties make nanofluidic ion channel membranes promising in various applications, including water purification, − energy conversion, − molecular sensing, , and resource recovery. , Among them, the nanofluidic energy harvesting of salinity gradients has experienced considerable research interest in recent years due to its high energy conversion efficiency and power density. − Fundamental studies on single-pore nanofluidic membranes have shown that nanofluidic membranes promise to achieve an ultrahigh power output. − For example, a single-layered MoS 2 sheet with a single nanopore has achieved an output power density of 10 6 W/m 2 , which is several magnitudes higher than conventional ion-exchange membranes . Nevertheless, to scale up these single-nanopore devices for practical use, two major hurdles need to be overcome.…”