Enhanced energy harvesting via pore-engineered ultrathin Ni foam: NiCo LDH-coated hydrovoltaic generator

Abstract

Water-driven energy harvesting has emerged as a sustainable approach to address the increasing global demand for renewable energy by utilizing abundant and eco-friendly resources. Nickel foam (Ni foam) serves as an excellent platform for hydrovoltaic applications due to its high porosity, mechanical stability, and superior conductivity, which enable efficient water transport and ion diffusion. In this study, we introduce a novel hydrovoltaic electricity generator that combines mechanical pore engineering of ultrathin Ni foam with surface modification via nickel–cobalt layered double hydroxides (NiCo LDH). By reducing the pore diameter from 148 μm to 37 μm through mechanical compression, we significantly increased capillary pressure, promoting enhanced water retention and sustained ion diffusion. This structural modification also reduced the evaporation rate, extending the hydration state and improving charge separation efficiency. This synergistic approach—integrating macro-scale structural control with nano-scale surface chemistry—enabled an eightfold enhancement in energy output (117.56 μWh/cm3) compared to uncoated Ni foam, and further optimization of the NiCo LDH coating led to a peak energy generation of approximately 550 μWh/cm3. Numerical simulations validated these findings, highlighting the interplay between capillary-driven water transport and controlled evaporation in optimizing hydrovoltaic performance. Our work provides the first experimental demonstration of a compression-driven design strategy for hydrovoltaic energy harvesting, offering a scalable and tunable platform for sustainable water-based electricity generation using nanostructured materials.