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•Wood-based Al-air batteries designed for miniaturized power sources.•Photothermal evaporation drives electrolyte flow through porous electrodes.•Integration of 3D wood-based ...microfluidics with solar energy utilization.•Impressive peak power density of 230 mW cm−3.•Stable discharge for over 11 h, ideal for long-lasting power supply.
Capillary microfluidics on porous substrates emerges as an innovative platform for constructing miniaturized electronics. However, maintaining a steady flow within microfluidics remains challenging, thus limiting their practical applications. Inspired by plant transpiration, this work presents a novel wood-based microfluidic Al-air battery (μAAB) configuration driven by a photothermal evaporator (biomimetic “leaf”). Except for the Al anode, the μAAB features an all-wood design, utilizing the well-aligned microchannels of the natural wood for electrolyte transportation, partially charred wood as photothermal evaporator for flow regulating, and wood-derived self-standing carbon cathode for the oxygen reduction reaction. These components are assembled through mortise-and-tenon joints, and the resulting μAAB exhibits a remarkable peak power density of 230 mW cm−3. The superior performance stems from the boosted mass transfer, maximized electrochemical interface and minimized depletion boundary layer provided by the 3D channeled structure of the wood-derived cathode. A steady discharge for over 11 h (200 mA cm−3) is obtained via the continuous electrolyte flow which is facilitated by the photothermal evaporator in the μAAB. This work not only presents a novel concept for miniaturized microfluidic power sources but also highlights the potential of 3D wood-based microfluidics combined with solar energy utilization.
Abstract Wood‐derived carbons demonstrate great potential as self‐standing electrodes in energy storage/conversion applications, including supercapacitors and water‐splitting devices. However, the ...key challenge remains the rational customization of surface functionalities for optimized performance. This study introduces an innovative approach to self‐standing wood‐derived carbons with tailored nitrogen and metal functionalities. In contrast to traditional impregnation techniques, which offer limited precision in surface modification, this approach entails the intentional attachment of amidoxime groups to the wood substrates. These groups serve as nitrogen sources, and create abundant surface anchoring sites for metal ions due to the chelation between the amidoxime groups and metals. The resulting carbons feature uniform and high dispersion of nitrogen and metal functionalities, along with a distinctive hierarchical porosity combining interconnected open channels with abundant mesopores. As a proof‐of‐concept, different metals are incorporated (i.e., Mn, Co, Ni) into the amidoximated‐wood precursors, and the resulting self‐standing carbons showcase excellent performance in both supercapacitors and water‐splitting applications. Leveraging the specific chelating ability of amidoxime groups toward metal ions, this strategy holds great potential as a generic approach to systematically tailoring the surface functionalities of carbon‐based materials for various electrochemical energy storage/conversion processes.
