Gradient electrospun carbon nanomembranes with tailored interface convection: A platform for multiphysics applications

The construction and regulation of three-phase interfaces dominate interfacial mass and heat transfer, and regulating interfacial convection at structurally gradient interfaces remains a critical unsolved scientific challenge. Herein, multi-walled carbon nanotube-doped polyacrylonitrile-based carbon nanomembranes with gradient pore size and fiber diameter were prepared via gradient electrospinning. Combined with COMSOL Multiphysics simulations and experimental characterizations, we investigated the gas-liquid two-phase transport mechanism of the gradient structure, which realized synergistic regulation of gas-liquid transport, ion migration and heat transfer at the three-phase interface via capillary pressure gradient. The gradient membrane electrode showed a low overpotential of 347 mV at 30 mA cm -2 for oxygen evolution, with superior cycling stability. For seawater desalination, it achieved a stable evaporation rate of 0.166 g/(cm 2 ·h) and a solar evaporation efficiency of 76.8% under 1000 W simulated sunlight via optimized water transport and reduced heat loss. This work offers a new structural design strategy for multifunctional membrane materials, deepens the understanding of mass and heat transfer at gradient three-phase interfaces, and lays a theoretical and experimental foundation for energy conversion and environmental treatment devices. • Gradient electrospun carbon nanomembranes with tailored pore size/porosity are fabricated, creating capillary pressure gradients to accelerate bubble desorption and directional water transport at three-phase interfaces. • The gradient membranes exhibit superior OER performance with lower overpotential and excellent durability, and achieve a stable seawater evaporation rate of 0.166 g/(cm 2 ∙h) with 76.8% efficiency. • Multiphysics simulations reveal the mechanisms of enhanced heat/mass transfer in gradient structures, providing a rational design strategy for electrocatalysis and desalination devices.