Biological electrogenic systems use protein‐based ionic pumps to move salt ions uphill across a cell membrane to accumulate an ion concentration gradient from the equilibrium physiological environment. Toward high‐performance and robust artificial electric organs, attaining an antigradient ion transport mode by fully abiotic materials remains a great challenge. Herein, a light‐driven proton pump transport phenomenon through a Janus graphene oxide membrane (JGOM) is reported. The JGOM is fabricated by sequential deposition of graphene oxide (GO) nanosheets modified with photobase (BOH) and photoacid (HA) molecules. Upon ultraviolet light illumination, the generation of a net protonic photocurrent through the JGOM, from the HA‐GO to the BOH‐GO side, is observed. The directional proton flow can thus establish a transmembrane proton concentration gradient of up to 0.8 pH units mm−2 membrane area at a proton transport rate of 3.0 mol h−1 m−2. Against a concentration gradient, antigradient proton transport can be achieved. The working principle is explained in terms of asymmetric surface charge polarization on HA‐GO and BOH‐GO multilayers triggered by photoisomerization reactions, and the consequent intramembrane proton concentration gradient. The implementation of membrane‐scale light‐harvesting 2D nanofluidic system that mimics the charge process of the bioelectric organs makes a straightforward step toward artificial electrogenic and photosynthetic applications.
Nanofluidic ion transport through van der Waals heterostructures, composed of two or more types of reconstructed 2D nanomaterials, gives rise to fascinating opportunities for light‐energy harvesting, due to coupling between the optoelectronic properties of the layered constituents and ion transport in between the atomic layers. Here, a photoinduced active ion transport phenomenon through transition metal dichalcogenides (TMDs)‐based van‐der‐Waals‐like multilayer heterostructures is reported for harnessing ionic power from equilibrium electrolyte solution. The binary heterostructure comprises sequentially stacked 2D‐WS2 and 2D‐MoS2 multilayers with sub‐1 nm interlayer spacing. Upon visible‐light illumination, a net ionic flow is initiated through the Janus membrane, suggesting a directional cationic transport from WS2 to MoS2 part. The transport mechanism is explained in terms of a photovoltaic effect due to type II band alignment of WS2/MoS2 heterostructures. The driving mechanism can be generally applied to a variety of heterogeneous TMD membranes with type II semiconductor heterojunctions. In equilibrium ionic solutions, the maximum ionic photoresponse approaches ≈21 µA cm–2 and ≈45 mV under one sun equivalent excitation. Under optimized conditions, the harvested power density reaches 2 mW m–2. The proof‐of‐concept demonstration of photonic‐to‐ionic power generation within angstrom‐scale confinement anticipates potential for light‐controlled ionic circuits, artificial photosynthesis, and biomimetic energy conversion.
2D nanofluidic systems are endowed with photo-responsive ionic rectification by asymmetric modification with spiropyran. Structural and photo-induced charge heterostructures result in smart 2D ionic rectifiers with a maximum rectification ratio of 48.
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