Ultrathin, lightweight, and flexible electromagnetic interference (EMI) shielding materials are urgently demanded to address EM radiation pollution. Efficient design to utilize the shields' microstructures is crucial yet remains highly challenging for maximum EMI shielding effectiveness (SE) while minimizing material consumption. Herein, novel cellular membranes are designed based on a facile polydopamine‐assisted metal (copper or silver) deposition on electrospun polymer nanofibers. The membranes can efficiently exploit the high‐conjunction cellular structures of metal and polymer nanofibers, and their interactions for excellent electrical conductivity, mechanical flexibility, and ultrahigh EMI shielding performance. EMI SE reaches more than 53 dB in an ultra‐broadband frequency range at a membrane thickness of merely 2.5 µm and a density of 1.6 g cm−3, and an SE of 44.7 dB is accomplished at the lowest thickness of 1.2 µm. The normalized specific SE is up to 232 860 dB cm2 g−1, significantly surpassing that of other shielding materials ever reported. More, integrated functionalities are discovered in the membrane, such as antibacterial, waterproof properties, excellent air permeability, high resistance to mechanical deformations and low‐voltage uniform heating performance, offering strong potential for applications in aerospace and portable and wearable smart electronics.

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CO partial current densities of 144 [6g] and 147 mA cm −2 , [7a] respectively.Here, we investigate the electrocatalytic performance and stability of a GDE design for the electrocatalytic reduction of gaseous CO 2 employing earth-abundant tin/copper (Sn/Cu) catalysts. Sn-decorated Cu surfaces were shown previously to provide high selectivity for CO 2 to CO conversion in aqueous electrolyte and achieve CO partial current densities of up to 11.5 mA cm −2 . [8] However, at higher current densities, the hydrogen evolution reaction (HER) starts to dominate due to insufficient CO 2 supply. [8b] To enhance CO 2 mass transport, we develop a process to fabricate electrospun polyvinylidene fluoride (PVDF) nanofibers with uniform Cu coating, and employ electrochemical underpotential deposition (UPD) of Sn to decorate the Cu surface. We demonstrate that Sn/Cu-coated PVDF (Sn/Cu-PVDF) nanofiber GDEs have CO faradaic efficiencies (FEs) above 80%, and achieve high CO partial current densities of up to 104 mA cm −2 , representing the highest reported current density for a Sn/Cu-based catalyst for CO 2 RR to CO.We employ electrospun PVDF nanofiber membranes as templates for fabricating freestanding Cu-nanofiber electrodes (Figure 1; Figure S1, Supporting Information). The PVDF surface is activated by grafting a self-assembled polydopamine (pDA) layer. [9] The pDA layer provides nuclei for electroless Cu deposition from a precursor consisting of 50 × 10 −3 m Cu(II) ethylenediaminetetraacetate (Cu-EDTA) and 0.1 m borane dimethylamine complex. After a reaction at 35 °C for 2 h, conformally Cu-coated PVDF (Cu-PVDF) nanofibers form a conductive network with a sheet resistivity lower than 2.41 Ω. UPD, providing 2D deposition control, is employed to decorate the Cu-PVDF nanofibers with Sn. Control over the exact amount of Sn is critical to obtain high selectivity for CO 2 RR to CO. [8a,b] On CO-selective Sn/Cu catalysts, the initial intermediate of the CO 2 RR is proposed to bind to the surface via the carbon (*COOH). [8g,10] When the amount of Sn on the Cu surface exceeds the optimal value, CO 2 binds to the surface preferentially via the oxygen forming a bidentate *OCHO intermediate, [8g,10] and behaves similarly to a Sn electrode which is selective for HCOO − . [8c-g,11] To quantify the coverage of deposited Sn by UPD, we make use of a polycrystalline Cu rotating disk electrode with an electrochemical surface area of 0.686 cm 2 . Sn UPD from an Ar-saturated 1 × 10 −3 m SnSO 4 + 0.1 m H 2 SO 4 solution correlates to the reduction peak tailing to Earth-abundant Sn/Cu catalysts are highly selective for the electrocatalytic reduction of CO 2 to CO in aqueous electrolytes. However, CO 2 mass transport limitations, resulting from the low solubility of CO 2 in water, so far limit the CO partial current density for Sn/Cu catalysts to about 10 mA cm −2 . Here, a freestanding gas diffusion electrode design based on Sn-decorated Cu-coated electrospun polyvinylidene fluoride nanofibers is demonstrated. The use of gaseous CO 2 as a feedst...