Newly N-S-C coordination-structured active sites, originating from the integrity of edged thiophene S, graphitic N, and pentagon defects, were reconstructed by N-modified S defects in carbon aerogel with a 3D hierarchical macro-mesomicroporous structure. This metal-free material exhibited outstanding oxygen reduction reaction (ORR) activity (e.g., half-wave potentials of 0.76 V in 0.5 M H 2 SO 4 and 0.1 M HClO 4 ; 0.85 V in 0.1 M KOH) with good stability and high current density in both acidic and alkaline electrolytes. The experimental and computational results reveal that the pentagon S defect is essential for the ORR in acidic electrolytes because it provides a remarkable increase in reactivity. One graphitic-type N in the meta-position of the pentagon defect further significantly improves the reactivity as a result of locally precise control of the electronic structure, thus forming highly active sites for ORR in acid.

Defective or heteroatom-doped metal-free carbon materials (MFCMs) have been regarded as efficient oxygen reduction reaction (ORR) catalysts in the past decade. However, the active centers for ORR in MFCMs are hard to confirm precisely and synthesize controllably through common methods such as high-temperature pyrolysis or heteroatom doping. To verify the precise structure acting as the active center for the ORR, we first report two crystalline metal-free thiophene-sulfur covalent organic frameworks (MFTS-COFs) as ORR catalysts. The MFTS-COFs show more positive catalytic capability than the thiophenefree COF, indicating that pentacyclic thiophene-sulfur building blocks act as active centers to induce ORR catalytic activity. MFTS-COFs with higher contents of thiophene-sulfur exhibit better ORR performance. The experimental identification is supported by density functional theory calculations. These results thus demonstrate that rational design and precise synthesis of metal-free crystalline organic materials can promote the development of new ORR catalysts.

The development of three-dimensional (3D) functionalized covalent organic frameworks (COFs) is of critical importance for expanding their potential applications. However, the introduction of functional groups in 3D COFs remains largely unexplored. Herein we report the first example of 3D Salphenbased COFs (3D-Salphen-COFs) and their metal-containing counterparts (3D-M-Salphen-COFs), the later being further used as catalytic antioxidants. These Salphen-based COFs exhibit high crystallinity and specific surface area in addition to excel lent chemical stability. Furthermore, the Cu(II)-Salphen COF displayed high activity in the removal of superoxide radicals. This study not only presents a new pathway to construct 3D functionalized COFs, but also promotes their applications in biology and medicine.

The functionalization of three-dimensional (3D) covalent organic frameworks (COFs) is essential to broaden their applications. However, the introduction of organic groups with electroactive abilities into 3D COFs is still very limited. Herein we report the first case of 3D tetrathiafulvalene-based COFs (3D-TTF-COFs) with non- or 2-fold interpenetrated pts topology and tunable electrochemical activity. The obtained COFs show high crystallinity, permanent porosity, and large specific surface area (up to 3000 m2/g). Furthermore, these TTF-based COFs are redox active to form organic salts that exhibit tunable electric conductivity (as high as 1.4 × 10–2 S cm–1 at 120 °C) by iodine doping. These results open a way toward designing 3D electroactive COF materials and promote their applications in molecular electronics and energy storage.

can provide a promising strategy for green usage of CO 2 from the atmosphere. [6][7][8][9] The concept of aprotic lithium-CO 2 battery is proposed, in which the mechanism is based on the electrochemical reaction, 4Li + + 3CO 2 + 4e -<=> 2Li 2 CO 3 + C (E o = 2.80 V vs Li/Li + ), composed of CO 2breathing electrode as cathodes, lithium metal as anodes, and lithium salt dissolved in aprotic solvent as electrolyte. [6,9,10] Although the specific pathway of CO 2 reduction reaction is still unclear, it is generally accepted that the reduction reaction proceeds through the general steps shown below [8,9,11,12] ) has been proved to form on the electrode at the beginning of discharge process by the in situ surface-enhanced Raman spectroscopy. [11] And the mechanism of the electroreduction of CO 2 in aprotic solvents has also been reported, in which the CO 2 is reduced to CO 2 by one-electron reaction, Aprotic Li-CO 2 batteries are a new class of green energy storage and conversion system, which can utilize the CO 2 from the atmosphere in an environmentally friendly way. However, the biggest problem of the existing Li-CO 2 batteries is that they suffer from high polarization and poor cycling performance, mainly caused by the insulating and insoluble discharge product, Li 2 CO 3 . Herein, this study reports the synthesis of wrinkled, ultrathin Ir nanosheets fully anchored on the surface of N-doped carbon nanofibers (Ir NSs-CNFs) as an efficient cathode for improving the performance of lithium-CO 2 batteries. The battery can be steadily discharged and charged at least for 400 cycles with a cut-off capacity of 1000 mAh g −1 at 500 mA g −1 . Meanwhile, the cathode can effectively reduce the charge overpotential by showing a charge termination voltage below 3.8 V at 100 mA g −1 , which is the smallest charge overpotential reported to date. The ex situ analysis of the intermediate products reveals that during the discharge process, Ir NSs-CNFs can greatly stabilize amorphous granular intermediate (probably Li 2 C 2 O 4 ) and delay its further transformation into thin plate-like Li 2 CO 3 , whereas during the charge process, it can make Li 2 CO 3 be easily and completely decomposed, which is the key in greatly improving its performance for lithium-CO 2 batteries. Lithium-CO 2 BatteriesThe energy shortage and environmental pollution are the severe challenges for achieving the sustainable development of the human society. [1,2] Unfortunately, the main energy resources in the present society are still fossil fuels, which undoubtedly are nonrenewable, and produce a mass of greenhouse gases, resulting in accelerating the global temperature rise. [3][4][5] How to capture and convert CO 2 into renewable energy in an environmentally friendly way is attracting more intensive attention.Recently, the lithium-CO 2 battery as an innovative energy storageThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.

The electrochemical double‐layer capacitors (EDLCs) are highly demanded electrical energy storage devices due to their high power density with thousands of cycle life compared with pseudocapacitors and batteries. Herein, a series of capacitor cells composed of exfoliated mesoporous 2D covalent organic frameworks (e‐COFs) that are able to perform excellent double‐layer charge storage is reported. The selected mesoporous 2D COFs possess eclipsed AA layer‐stacking mode with 3.4 nm square‐like open channels, favorable BET surface areas (up to 1170 m2 g−1), and high thermal and chemical stabilities. The COFs via the facile, scalable, and mild chemical exfoliation method are further exfoliated to produce thin‐layer structure with average thickness of about 22 nm. The e‐COF‐based capacitor cells achieve high areal capacitance (5.46 mF cm−2 at 1,000 mV s−1), high gravimetric power (55 kW kg−1), and relatively low τ0 value (121 ms). More importantly, they perform nearly an ideal DL charge storage at high charge–discharge rate (up to 30 000 mV s−1) and maintain almost 100% capacitance stability even after 10 000 cycles. This study thus provides insights into the potential utilization of COF materials for EDLCs.

8487wileyonlinelibrary.com high-performance energy storage due to its limited control over specific surface area and insufficient porous channels. [5] And also, the current carbon-based energy storage materials suffer from poor kinetic problems associated with the inner-pore ion transports. [4] Tuning/ optimizing the pore shape, the pore sizes distribution, and the pore connectivity in carbon nanomaterials are very important for improving the electrochemical performance. [6] The hierarchically porous carbon (HPC) materials with optimized micro-, meso-, and macropores are considered to be ideal electrode materials for efficient energy storage. [7,8] Particularly, the mesopores in HPC materials can provide the low-resistant pathways for the ions through the porous particles. The ion-buffering reservoirs can be formed in the macropores that can minimize the ions diffusion distances between the interior surfaces. [9,10] Currently, the regular method to fabricate HPC is the use of hard templates. [11] However, the traditional strategies for fabricating hierarchical architectures hamper their commercial utilization due to the complicated preparation procedure and the involvement of expensive nonrenewable templates. It is still a great challenge for developing a template-free, ecofriendly, and scalable approach to fabricate HPC materials from readily available carbon sources, especially from renewable biomass.The increasing demand for efficient energy storage and conversion devices has aroused great interest in designing advanced materials with high specific surface areas, multiple holes, and good conductivity. Here, we report a new method for fabricating a hierarchical porous carbonaceous aerogel (HPCA) from renewable seaweed aerogel. The HPCA possesses high specific surface area of 2200 m 2 g −1 and multilevel micro/meso/macropore structures. These important features make HPCA exhibit a reversible lithium storage capacity of 827.1 mAh g −1 at the current density of 0.1 A g −1 , which is the highest capacity for all the previously reported nonheteroatom-doped carbon nanomaterials. It also shows high specific capacitance and excellent rate performance for electric double layer capacitors (260.6 F g −1 at 1 A g −1 and 190.0 F g −1 at 50 A g −1 ), and long cycle life with 91.7% capacitance retention after 10 000 cycles at 10 A g −1 . The HPCA also can be used as support to assemble Co 3 O 4 nanowires (Co 3 O 4 @HPCA) for constructing a high performance pseudocapacitor with the maximum specific capacitance of 1167.6 F g −1 at the current density of 1 A g −1 . The present work highlights the first example in using prolifera-green-tide as a sustainable source for developing advanced carbon porous aerogels to achieve multiple energy storage.Adv. Funct. Mater. 2016, 26, 8487-8495 www.afm-journal.de www.MaterialsViews.com Scheme 1. Scheme diagram for the fabrication of the hierarchically porous carbon. EP fibers were decolorized and freeze-dried to get the aerogel of EP. Precarbonized at 700 °C and then activated at 700, 800, a...

Carbon nanomaterials with both doped heteroatom and porous structure represent a new class of carbon nanostructures for boosting electrochemical application, particularly sustainable electrochemical energy conversion and storage applications. We herein demonstrate a unique large-scale sustainable biomass conversion strategy for the synthesis of earth-abundant multifunctional carbon nanomaterials with well-defined doped heteroatom level and multimodal pores through pyrolyzing electrospinning renewable natural alginate. The key part for our chemical synthesis is that we found that the egg-box structure in cobalt alginate nanofiber can offer new opportunity to create large mesopores (∼10–40 nm) on the surface of nitrogen-doped carbon nanofibers. The as-prepared hierarchical carbon nanofibers with three-dimensional pathway for electron and ion transport are conceptually new as high-performance multifunctional electrochemical materials for boosting the performance of oxygen reduction reaction (ORR), lithium ion batteries (LIBs), and supercapacitors (SCs). In particular, they show amazingly the same ORR activity as commercial Pt/C catalyst and much better long-term stability and methanol tolerance for ORR than Pt/C via a four-electron pathway in alkaline electrolyte. They also exhibit a large reversible capacity of 625 mAh g–1 at 1 A g–1, good rate capability, and excellent cycling performance for LIBs, making them among the best in all the reported carbon nanomaterials. They also represent highly efficient carbon nanomaterials for SCs with excellent capacitive behavior of 197 F g–1 at 1 A g–1 and superior stability. The present work highlights the importance of biomass-derived multifunctional mesoporous carbon nanomaterials in enhancing electrochemical catalysis and energy storage.