Cascade‐Heterostructured Nanofluidics for Photo‐Enhanced Upscaling Osmotic Energy Generation

ABSTRACT Ensuring energy and resource availability constitutes a fundamental pillar of sustainable socioeconomic development. Nanofluidics hold great promise for energy and resource harvesting. However, a critical bottleneck hinders commercialization, namely, that upscaling nanofluidic areas to boost ion currents triggers severe potential drop and concentration polarization, causing a drastic degradation in selectivity. Here, we engineered cascade‐heterostructured nanofluidics (CHS‐NFs) featuring numerous atomic‐level type‐I semiconductor heterojunctions and Schottky junctions to create continuous, ultrafast pathways for coupled electron‐ion transport. The heterointerfaces generate nanoscale localized asymmetric electric fields that mitigate concentration polarization and offset potential drops, thereby realizing high ion selectivity and flux. As a result, the CHS‐NFs achieve a record‐high energy conversion efficiency of 49.5%—approaching the theoretical limit of 50%—over a large area (28 mm 2 , 933 times larger than prior areas), with an exceptional Na + /Cl − selectivity of 332.3. The electricity produced by CHS‐NFs‐based osmotic cells is effectively stored in capacitors and ion batteries under simulated solar irradiation, exhibiting a 68.8% capacity increase compared with a non‐irradiated one. Notably, the cells can generate a high ionic current (467.6 µA), enabling the selective electrochemical recovery of gold from solutions with near‐100% purity, as well as other valuable metals, significantly reducing the energy footprint of industrial metallurgy.