Gradience Free Nanoinsertion of Fe₃O₄ into Wood for Enhanced Hydrovoltaic Energy Harvesting

Hydrovoltaic energy harvesting offers the potential to utilize enormous water energy for sustainable energy systems. Here, we report the utilization and tailoring of an intrinsic anisotropic 3D continuous microchannel structure from native wood for efficient hydrovoltaic energy harvesting by Fe₃O₄ nanoparticle insertion. Acetone-assisted precursor infiltration ensures the homogenous distribution of Fe ions for gradience-free Fe₃O₄ nanoparticle formation in wood. The Fe₃O₄/wood nanocomposites result in an open-circuit voltage of 63 mV and a power density of ∼52 μW/m² (∼165 times higher than the original wood) under ambient conditions. The output voltage and power density are further increased to 1 V and ∼743 μW/m² under 3 suns solar irradiation. The enhancement could be attributed to the increase of surface charge, nanoporosity, and photothermal effect from Fe₃O₄. The device exhibits a stable voltage of ∼1 V for 30 h (3 cycles of 10 h) showing good long-term stability. The methodology offers the potential for hierarchical organic-inorganic nanocomposite design for scalable and efficient ambient energy harvesting.