Advancing Hydrovoltaic Energy Harvesting from Wood through Cell Wall Nanoengineering

Abstract

Converting omnipresent environmental energy through the assistance of spontaneous water evaporation is an emerging technology for sustainable energy systems. Developing bio-based hydrovoltaic materials further pushes the sustainability, where wood is a prospect due to its native hydrophilic and anisotropic structure. However, current wood-based water evaporation-assisted power generators are facing the challenge of low power density. Here, an efficient hydrovoltaic wood power generator is reported based on wood cell wall nanoengineering. A highly porous wood with cellulosic network filling the lumen is fabricated through a green, onestep treatment using sodium hydroxide to maximize the wood surface area, introduce chemical functionality, and enhance the cell wall permeability of water. An open-circuit potential of ≈140 mV in deionized water is realized, over ten times higher than native wood. Further tuning the pH difference between wood and water, due to an ion concentration gradient, a potential up to 1 V and a remarkable power output of 1.35 µW cm −2 is achieved. The findings in this study provide a new strategy for efficient wood power generators.

Surface Carbonized Natural Wood via Hydrogen–Oxygen Flame for Electricity Generation from Water Evaporation

“…Driven by a concentration gradient that diffused from the top to bottom, H + migration opposite to the direction of flow was formed, resulting conduction current. 41 At steady state, the conduction current equaled the traditional streaming current and established a maximum potential across the wood device. The surface carbonization strategy enhanced the electrical performance of the SCW-EIPG, which could be attributed to the synergistic effect of the surface carbonized layer and the internal non-carbonized layer: the inner layer of the SCW-EIPG maintained high hydrophilicity to carry out a stable capillary flow and a higher surface potential to form an EDL ensuring high selectivity of the channel for positive ions, which could promote the directional movement of H + in the channel; the surface carbonized layer provided an electron transport path to reduce the internal resistance of SCW-EIPG and enhanced the EDL effect at the water−channel interface due to the absorption of H + .…”

“…When the EDL was overlapped, there would exist massive H + in the channel of wood which moved with water flow and was enriched at the upper end of the device to establish a polarization distribution, as shown in Figure b. Driven by a concentration gradient that diffused from the top to bottom, H + migration opposite to the direction of flow was formed, resulting conduction current . At steady state, the conduction current equaled the traditional streaming current and established a maximum potential across the wood device.…”

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

“…Recently, our group reported hydrovoltaic energy harvesting from charged nanoporous wood aerogel in a water reservoir at a pH of 13.4. A V oc of 0.55 V and power density of 620 μW/m 2 were obtained under ambient conditions, 19 indicating the potential of wood nanostructure control for enhanced power generation. Further tailoring nanoengineered wood pH resulted in a V oc of 1 V. Current reports of wood for water evaporation-induced power generation were based on lignocellulose or carbon (carbonized wood) interfacial interactions with water, which shows limited water charge separation abilities.…”

Electricity Generation from Phase Transitions between Liquid and Gaseous Water

“…The sandwiched structure normally utilizes a porous top electrode which allows for water permeation and evaporation. [59][60][61][62][63] As water molecules evaporate from the top electrode surface, the inner water capillary flow within the nanochannels of active materials can be induced and electricity is continuously generated throughout the materials.…”