Janus Membrane-Based Hydrovoltaic Power Generation with Enhanced Performance under Suppressed Evaporation Conditions

Abstract

We developed a novel hydrovoltaic power generator (HPG) using a Janus bilayer membrane with an asymmetric wettability. The Janus bilayer membrane was fabricated by stacking a hydrophobic graphene oxide (GO)-cellulose nanofiber (CNF) composite layer on a hydrophilic GO−CNF composite layer. Water supplied through the hydrophilic layer stops at the surface of the hydrophobic layer, producing separate wet and dry regions within the thin bilayer. Protons and sodium ions dissociate from oxygencontaining functional groups in the hydrophilic GO−CNF layer and migrate toward the hydrophobic layer, resulting in a maximum output voltage and current of 0.35 V and 20 μA, respectively, in deionized (DI) water. By replacement of DI water with a 0.6 M NaCl solution (i.e., the concentration of seawater), the output voltage and current were further increased to 0.55 V and 60 μA, respectively. This performance was consistent not only under low humidity due to the water supply but also under high humidity, where evaporation was restricted, indicating humidity-independent performance. The asymmetric wettability of the membrane remained stable throughout the experiment (7 days), enabling continuous power generation.

Assembly of Natural Clay Minerals as Highly Robust Evaporation-Driven Power Generator

“…Fluids flowing through micro- and nanochannels induce streaming of ionic current, which is attributed to an electrical double layer at the solid–liquid interface. Carbon-based materials like carbon soot, graphene oxide, and carbon films are top choices for this application. , These carbon nanomaterial-based generators rely on the gradient of water flowing through narrow pores or channels within the carbon particles, converting ambient thermal energy into electricity. Several polymers, proteins, and layered double-hydroxide-based materials were also proven successful in generating electrical power via the evaporation process at microwatts per cubic centimeter levels. − While these achievements are promising, these generators often involve complicated system designs or sophisticated material processing techniques, such as annealing and plasma treatments, which increase the cost and complexity of the fabrication process.…”