Synergistic Photoelectric/Photothermal Effects Guided Ion Transport for Enhancing Multiple Climatic Osmotic Energy Conversion Efficiency

Abstract

Osmotic energy, also called blue energy, promotes sustainable energy development. Nanofluidic membranes constructed from various nanomaterials applied in reverse electrodialysis play an important role in enhancing the effective osmotic energy conversion. The fabrication of g-C₃N₄ modified MXene/regenerated cellulose composite nanofluidic membranes is developed. Optimization of advanced membrane structure not only designed a well-ordered layer arrangement resulting in low membrane impedance but also enabled photoelectric/photothermal guided ion transport to promote energy conversion. The photoelectric effect promoted the separation of electrons and holes between g-C₃N₄ and MXene to form a local electric field, causing the output current of thenanofluidic membrane-based reverse electrodialysis to jump sharply from 17 µA to a peak current of 28 µA (no light to light) and increasing the power density from 0.9 W m⁻² to 4.3 W m⁻². After 1200 s of illumination, the MXene channel created an inhomogeneous temperature gradient that triggered ion transport driven by thermal osmosis through the photothermal effect, resulting in an excellent output power density of 5.9 W m⁻². Photoelectric/photothermal enhanced osmotic energy harvesting over multiple climate changes. Thus, this work expands the way of photoelectric/photothermal guided ion transport to enhance the conversion of osmotic energy into electrical energy.