Ultrastable Surface-Dominated Pseudocapacitive Potassium Storage Enabled by Edge-Enriched N-Doped Porous Carbon Nanosheets

The development of ultrastable carbon materials for potassium storage poses key limitations caused by the huge volume variation and sluggish kinetics. Nitrogen-enriched porous carbons have recently emerged as promising candidates for this application; however, rational control over nitrogen doping is needed to further suppress the long-term capacity fading. Here we propose a strategy based on pyrolysis–etching of a pyridine-coordinated polymer for deliberate manipulation of edge-nitrogen doping and specific spatial distribution in amorphous high-surface-area carbons; the obtained material shows an edge-nitrogen content of up to 9.34 at %, richer N distribution inside the material, and high surface area of 616 m² g⁻¹ under a cost-effective low-temperature carbonization. The optimized carbon delivers unprecedented K-storage stability over 6000 cycles with negligible capacity decay (252 mA h g⁻¹ after 4 months at 1 A g⁻¹), rarely reported for potassium storage.     

Dual-Templating Approaches to Soybeans Milk-Derived Hierarchically Porous Heteroatom-Doped Carbon Materials for Lithium-Ion Batteries

Biomass derived carbon materials are widely available, cheap and abundant resources. The application of these materials as electrodes for rechargeable batteries shows great promise. To further explore their applications in energy storage fields, the structural design of these materials has been investigated. Hierarchical porous heteroatom-doped carbon materials (HPHCs) with open three-dimensional (3D) nanostructure have been considered as highly efficient energy storage materials. In this work, biomass soybean milk is chosen as the precursor to construct N, O co-doped interconnected 3D porous carbon framework via two approaches by using soluble salts (NaCl/Na₂CO₃ and ZnCl₂/Mg₅(OH)₂(CO₃)₄, respectively) as hard templates. The electrochemical results reveal that these structures were able to provide a stable cycling performance (710 mAh ⋅ g⁻¹ at 0.1 A ⋅ g⁻¹ after 300 cycles for HPHC-a, and 610 mAh ⋅ g⁻¹ at 0.1 A ⋅ g⁻¹ after 200 cycles for HPHC-b) in Li-ion battery and Na-ion storage (210 mAh ⋅ g⁻¹ at 0.1 A ⋅ g⁻¹ after 900 cycles for HPHC-a) as anodes materials, respectively. Further comparative studies showed that these improvements in HPHC-a performance were mainly due to the honeycomb-like structure containing graphene-like nanosheets and high nitrogen content in the porous structures. This work provides new approaches for the preparation of hierarchically structured heteroatom-doped carbon materials by pyrolysis of other biomass precursors and promotes the applications of carbon materials in energy storage fields.     

Ice/Salt-Assisted Synthesis of Ultrathin Two-Dimensional Micro/Mesoporous Iron and Nitrogen Co-Doped Carbon as an Efficient Electrocatalyst for Oxygen Reduction

An ice/salt-assisted strategy has been developed to achieve the green and efficient synthesis of ultrathin two-dimensional (2D) micro/mesoporous carbon nanosheets (CNS) with the dominant active moieties of Fe−N₄ (Fe-N-CNS) as high-performance electrocatalysts for the oxygen reduction reaction (ORR). The strategy involves freeze-drying a mixture of iron porphyrin and KCl salt using ice as template followed by a confined pyrolysis with KCl as an independent sealed nanoreactor to facilitate the formation of 2D carbon nanosheets, N incorporation, and porosity creation. The well-defined assembly of ultrathin 2D carbon nanosheets ensures high utilization of D1 and D3 Fe−N₄ active sites, and effectively promotes the mass transport of ORR reactants by virtue of the pronounced mesoporous structure. The resulting Fe-N-CNS electrocatalyst was shown to exhibit superior ORR activity, better electrochemical durability, and methanol tolerance towards ORR in alkaline electrolyte relative to the commercial Pt/C electrocatalyst.     

氮硫共掺杂多孔碳材料的制备及其在锂硫电池中的应用

锂硫电池因其较高的理论容量和对环境友好等优势被视为极具发展潜力的储能装置,但是多硫化物的穿梭效应极大地限制了锂硫电池的实际应用。本文以葡萄糖为碳源,离子液体为氮源和硫源,KCl和ZnCl₂为模板剂,KOH为活化剂,通过热解工艺合成了氮硫共掺杂多孔碳（NSPC）。XPS和极性吸附实验表明N、S杂原子成功引入并且提高了碳材料对多硫化物的吸附能力,有效缓解多硫化物的穿梭效应,而较高的比表面积（1290.67 m²·g^-1）有助于提高硫负载量。负载70.1wt.%的硫后（S@NSPC）作为锂硫电池的正极材料表现出了良好的电化学性能。在167.5 mA·g^-1的电流密度下S@NSPC的首次放电容量为1229.2 mAh·g^-1,远高于S@PC的861.6 mAh·g^-1,且S@NSPC循环500圈后容量为328.1 mAh·g^-1。当电流密度从3350 mA·g^-1恢复至167.5 mA·g^-1时,可逆容量达到首圈放电比容量的80%,几乎恢复至其初始值。     

High‐Yield Electrosynthesis of Hydrogen Peroxide from Oxygen Reduction by Hierarchically Porous Carbon

H₂O₂ production by electroreduction of O₂ is an attractive alternative to the current anthraquinone process, which is highly desirable for chemical industries and environmental remediation. However, it remains a great challenge to develop cost‐effective electrocatalysts for H₂O₂ synthesis. Here, hierarchically porous carbon (HPC) was proposed for the electrosynthesis of H₂O₂ from O₂ reduction. It exhibited high activity for O₂ reduction and good H₂O₂ selectivity (95.0–70.2 %, most of them >90.0 % at pH 1–4 and >80.0 % at pH 7). High‐yield H₂O₂ generation has been achieved on HPC with H₂O₂ concentrations of 222.6–62.0 mmol L^?1 (2.5 h) and corresponding H₂O₂ production rates of 395.7–110.2 mmol h^?1 g^?1 at pH 1–7 and ?0.5 V. Moreover, HPC was energy‐efficient for H₂O₂ production with current efficiency of 81.8–70.8 %. The exceptional performance of HPC for electrosynthesis of H₂O₂ could be attributed to its high content of sp³‐C and defects, large surface area and fast mass transfer.     

Regulating Oxygen Configuration in Hierarchically Porous Carbon Nanosheets for High-Rate and Durable Na+ Storage

Surface oxygen functionalities (particularly C−O configuration) in carbon materials have negative influence on their electrical conductivity and Na⁺ storage performance. Herein, we propose a concept from surface chemistry to regulate the oxygen configuration in hierarchically porous carbon nanosheets (HPCNS). It is demonstrated that the C−O/C=O ratio in HPCNS reduces from 1.49 to 0.43 and its graphitization degree increases by increasing the carbonization temperature under a reduction atmosphere. Remarkably, such high graphitization degree and low C−O content of the HPCNS-800 are favorable for promoting its electron/ion transfer kinetics, thus endowing it with high-rate (323.6 mAh g⁻¹ at 0.05 A g⁻¹ and 138.5 mAh g⁻¹ at 20.0 A g⁻¹) and durable (96 % capacity retention over 5700 cycles at 10.0 A g⁻¹) Na⁺ storage performance. This work permits the optimization of heteroatom configurations in carbon for superior Na⁺ storage.     

柚子皮衍生的分级多孔碳作为高性能超级电容器的电极材料

使用CTAB作为软模板,水热处理柚子皮,再以碳化和KOH活化过程得到了分级多孔碳(HPC),这种分级多孔碳材料的比表面积高达1 813 m~2·g~(-1),相比于没有水热步骤制备的多孔碳(PC),拥有更加丰富的介孔结构和更大的比表面积。XPS分析结果表明HPC的氧掺杂量更高,会比PC贡献更大的赝电容。三电极测试体系中,HPC的比电容达到285 F·g~(-1)(0.5 A·g~(-1),1 mol·L~(-1)KOH)。同时,组装的两电极对称超级电容器拥有很好的倍率性能,循环12 000次充放电后,比电容依旧保留99%。HPC拥有这样优异的性能归结于较大的比表面积,高氧掺杂量和合理的孔径分布的协同作用。     

A Site‐Selective Doping Strategy of Carbon Anodes with Remarkable K‐Ion Storage Capacity

The limited potassium‐ion intercalation capacity of graphite hampers development of potassium‐ion batteries (PIB). Edge‐nitrogen doping is an effective approach to enhance K‐ion storage in carbonaceous materials. One shortcoming is the lack of precise control over producing the edge‐nitrogen configuration. Here, a molecular‐scale copolymer pyrolysis strategy is used to precisely control edge‐nitrogen doping in carbonaceous materials. This process results in defect‐rich, edge‐nitrogen doped carbons (ENDC) with a high nitrogen‐doping level (up to 10.5 at %) and a high edge‐nitrogen ratio (87.6 %). The optimized ENDC exhibits a high reversible capacity of 423 mAh g^?1, a high initial Coulombic efficiency of 65 %, superior rate capability, and long cycle life (93.8 % retention after three months). This strategy can be extended to design other edge‐heteroatom‐rich carbons through pyrolysis of copolymers for efficient storage of various mobile ions.     

B,N Co-Doped Three-Dimensional Carbon Aerogels with Excellent Electrochemical Performance for the Oxygen Reduction Reaction

Herein, an ordinary and mass-production approach is reported to synthesize boron (B) and nitrogen (N) co-doped three-dimensional (3D) carbon aerogels (CA) by using glucose and borax as the raw materials by a simple hydrothermal method and then carbonization in NH₃ atmosphere. The porous material (BN-CA-900) possesses a large specific surface area (1032 m² g⁻¹) and high contents of doped pyridinic N and graphitic N. The onset potential (0.91 V vs. reversible hydrogen electrode, RHE), half-wave potential (0.77 V vs. RHE), and current density (5.70 mA cm⁻² at 0.2 V vs. RHE) of BN-CA-900 for ORR are similar to those of commercial Pt/C, indicating that BN-CA-900 has a comparable catalytic activity with Pt/C in alkaline media. The number of electron transfer is 3.86–3.99 and the yield of hydrogen peroxide is less than 6.8 %. BN-CA-900 also presents decent catalytic performance in acidic medium. Moreover, the stability and methanol tolerance of BN-CA-900 are superior to commercial Pt/C in both alkaline and acidic media. The prepared BN-CA-900 is a promising candidate that may be applied in other areas, such as the adsorption of pollution, porous conductive electrodes, and lithium-ion batteries.     

Facile Synthesis of Ultra-Small Few-Layer Nanostructured MoSe2 Embedded on N,P Co-Doped Bio-Carbon for High-Performance Half/Full Sodium-Ion and Potassium-Ion Batteries

Sodium/potassium-ion batteries (SIBs/PIBs) arouse intensive interest on account of the natural abundance of sodium/potassium resources, the competitive cost and appropriate redox potential. Nevertheless, the huge challenge for SIBs/PIBs lies in the scarcity of an anode material with high capacity and stable structure, which are capable of accommodating large-size ions during cycling. Furthermore, using sustainable natural biomass to fabricate electrodes for energy storage applications is a hot topic. Herein, an ultra-small few-layer nanostructured MoSe₂ embedded on N, P co-doped bio-carbon is reported, which is synthesized by using chlorella as the adsorbent and precursor. As a consequence, the MoSe₂/NP-C-2 composite represents exceedingly impressive electrochemical performance for both sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs). It displays a promising reversible capacity (523 mAh g⁻¹ at 100 mA g⁻¹ after 100 cycles) and impressive long-term cycling performance (192 mAh g⁻¹ at 5 A g⁻¹ even after 1000 cycles) in SIBs, which are some of the best properties of MoSe₂-based anode materials for SIBs to date. To further probe the great potential applications, full SIBs pairing the MoSe₂/NP-C-2 composite anode with a Na₃V₂(PO₄)₃ cathode also exhibits a satisfactory capacity of 215 mAh g⁻¹ at 500 mA g⁻¹ after 100 cycles. Moreover, it also delivers a decent reversible capacity of 131 mAh g⁻¹ at 1 A g⁻¹ even after 250 cycles for PIBs.     

ZIF‐8 Derived Graphene‐Based Nitrogen‐Doped Porous Carbon Sheets as Highly Efficient and Durable Oxygen Reduction Electrocatalysts

Nitrogen‐doped carbon (NC) materials have been proposed as next‐generation oxygen reduction reaction (ORR) catalysts to significantly improve scalability and reduce costs, but these alternatives usually exhibit low activity and/or gradual deactivation during use. Here, we develop new 2D sandwich‐like zeolitic imidazolate framework (ZIF) derived graphene‐based nitrogen‐doped porous carbon sheets (GNPCSs) obtained by in situ growing ZIF on graphene oxide (GO). Compared to commercial Pt/C catalyst, the GNPCSs show comparable onset potential, higher current density, and especially an excellent tolerance to methanol and superior durability in the ORR. Those properties might be attributed to a synergistic effect between NC and graphene with regard to structure and composition. Furthermore, higher open‐circuit voltage and power density are obtained in direct methanol fuel cells.     

百香果皮基原位氮掺杂多孔碳/硫复合正极的制备及储锂性能

以生物质百香果皮为碳源,KHCO3为活化剂,采用同步活化碳化方法制备原位氮掺杂的分级多孔碳材料,将其与单质硫复合制得多孔碳/硫正极材料。通过X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)等表征技术对制备材料的物相组成、微观形貌、比表面积及孔结构进行研究分析。同时,利用紫外可见吸收光谱研究了多孔碳对多硫化物的吸附作用,用恒电流充放电测试了不同硫含量(60%～80%)的多孔碳/硫复合正极材料的电化学性能。结果表明,制得的多孔碳材料为无定型,具有1 093 m²·g^-1的高比表面积和0.63 cm³·g^-1的孔容;丰富的多孔结构和原位氮掺杂对多硫化物的物理化学协同吸附作用,有效降低了锂硫电池的“穿梭效应”,提高了电池的放电比容量和循环性能。硫含量为60%的多孔碳/硫复合材料,在0.05C和0.2C倍率下可释放1 057.7和763.4 mAh·g^-1的高初始放电比容量,在1C的高倍率下循环300次后的保持率为75%。     

铁镍合金纳米颗粒镶嵌的多级孔氮掺杂碳催化剂的制备及析氧性能研究

非贵金属铁镍合金催化剂在析氧反应（OER）中性能优异，表现出取代贵金属RuO₂催化剂的巨大潜力.以SiO₂为大孔模板，多巴胺为氮碳源，Fe³⁺，Ni²⁺为金属源，通过原位吸附、聚合、焙烧、刻蚀等步骤制备得到铁镍合金纳米颗粒镶嵌的多级孔氮掺杂碳催化剂.碱性介质中的析氧反应测试表明，合金催化剂达到电流密度10 mA·cm^-2时过电位仅为286 mV，显著低于以RuO₂为催化剂的380 mV过电位；同时经过2000圈循环伏安老化后活性几乎无衰减，稳定性高.所制备的合金催化剂具有两方面结构优势：（1）铁镍合金以及单质铁纳米颗粒镶嵌于大孔碳的薄层孔壁中，有利于暴露活性位点；（2）石墨化氮碳层对合金纳米颗粒的保护提高了材料抗腐蚀性，进而提升其稳定性.     

氮掺杂石墨烯量子点/MOF衍生多孔碳纳米片构筑高性能超级电容器

首先采用溶液法在碳布上生长Co-MOF二维纳米片,通过高温退火和刻蚀后得到MOF衍生多孔碳纳米片。以Co-MOF衍生的多孔碳纳米片/碳布(CNS/CC)作为碳基骨架,采用电化学沉积法负载高活性氮掺杂石墨烯量子点(N-GQDs),制备得到分级多孔结构的N-GQD/CNS/CC复合材料。组装成自支撑且无粘结剂的N-GQD/CNS/CC电极,当电流密度为1 A·g~(-1)时,其比电容高达423 F·g~(-1)。通过储能机制和电容贡献机制的研究表明,在碳纤维上原位生长的具有高双电层电容的CNS和表面负载具有高赝电容的N-GQDs之间相互协同作用,使得N-GQD/CNS/CC电极具有高电容性能,是一种理想的超级电容器电极材料。电极材料的高导电、分级多孔结构有利于电子的传输和电解质离子的扩散,具有良好的动力学性能,能快速充放电和具有优异的倍率特性。将电极组装成对称型超级电容器,功率密度为250 W·kg~(-1)时对应的能量密度达到7.9 Wh·kg~(-1),且经过10 000次循环后电容保持率为91.2%,说明氮掺杂石墨烯量子点/MOF衍生多孔碳纳米片复合材料是一种电化学性能稳定的具有高电容性能的全碳电极材料。     

Oxygen-Vacancy-Abundant Ferrites on N-Doped Carbon Nanosheets as High-Performance Li-Ion Battery Anodes

Transition metal oxides, as one of the most promising anode materials for lithium-ion batteries, often suffer from poor electronic conductivity and serious structural collapse. In this work, oxygen-vacancy-abundant CoFe₂O₄ and NiFe₂O₄ deposited on N-doped carbon nanosheets are designed and fabricated through a calcination procedure and a solvothermal strategy using Zn-hexamine coordination frameworks as precursors. The as-prepared NC@CoFe₂O₄ and NC@NiFe₂O₄ hybrids display improved cycle performances and rate capacities compared with CoFe₂O₄, NiFe₂O₄, and Fe₂O₃. The enhanced lithium storage performances of NC@CoFe₂O₄ and NC@NiFe₂O₄ are attributed to the oxygen vacancies and conductive N-doped carbon nanosheets, which increase the electronic conductivity and electrochemical reaction kinetics. The synthetic process in this work provides a new perspective for designing other high-performance transition metal oxide anodes.     

Free‐Standing Air Cathodes Based on 3D Hierarchically Porous Carbon Membranes: Kinetic Overpotential of Continuous Macropores in Li‐O2 Batteries

Free‐standing macroporous air electrodes with enhanced interfacial contact, rapid mass transport, and tailored deposition space for large amounts of Li₂O₂ are essential for improving the rate performance of Li‐O₂ batteries. An ordered mesoporous carbon membrane with continuous macroporous channels was prepared by inversely topological transformation from ZnO nanorod array. Utilized as a free‐standing air cathode for Li‐O₂ battery, the hierarchically porous carbon membrane shows superior rate performance. However, the increased cross‐sectional area of the continuous macropores on the cathode surface leads to a kinetic overpotential with large voltage hysteresis and linear voltage variation against Butler–Volmer behavior. The kinetics were investigated based on the rate‐determining step of second electron transfer accompanied by migration of Li⁺ in solid or quasi‐solid intermediates. These discoveries shed light on the design of the air cathode for Li‐O₂ batteries with high‐rate performance.     

蟹壳基氮/氧共掺杂多孔炭的原位制备及其超级电容器性能

采用废弃蟹壳为碳源,KOH为活化剂原位制备了氮/氧共掺杂多孔炭,并研究其作为电极材料在超级电容器中的应用。 固定蟹壳与KOH的质量比为5:3,考察了煅烧温度对所得炭材料产率、孔结构和氮氧含量的影响。 结果表明,蟹壳基炭材料的孔结构和氮/氧含量可通过改变煅烧温度调变。 随着煅烧温度从500 ℃上升至700 ℃,多孔炭的比表面积和孔体积逐渐增大,而氮/氧含量随温度升高则降低。 采用循环伏安和恒流充放电对所得材料的电化学性能进行测试。 结果表明,所得多孔炭的电化学性能取决于其孔结构与氮/氧表面性质的协同作用,其中煅烧温度为600 ℃所得的多孔炭比表面积为612 m²/g,氮和氧含量分别为3.53%和32.8%,在50 mA/g的电流密度下比电容达到310 F/g,循环1000次比电容仍然保持95%以上,展现出良好的电化学性能。     

Porous Nitrogen‐Doped Carbon Microspheres Derived from Microporous Polymeric Organic Frameworks for High Performance Electric Double‐Layer Capacitors

This research presents a simple and efficient method to synthesize porous nitrogen‐doped carbon microspheres (PNCM) by the carbonization of microporous poly(terephthalaldehyde‐pyrrole) organic frameworks (PtpOF). The common KOH activation process is used to tune the porous texture of the PNCM and produce an activated‐PNCM (A‐PNCM). The PNCM and A‐PNCM with specific surface area of 921 and 1303 m² g^?1, respectively, are demonstrated as promising candidates for EDLCs. At a current density of 0.5 A g^?1, the specific capacitances of the PNCM and A‐PNCM are 248 and 282 F g^?1, respectively. At the relatively high current density of 20 A g^?1, the capacitance remaining is 95 and 154 F g^?1, respectively. Capacity retention of the A‐PNCM is more than 92 % after 10 000 charge/discharge cycles at a current density of 2 A g^?1.     

活性位高度暴露的钴/氮/碳电催化剂的构建及氧还原性能研究

金属/氮/碳催化剂（M/N/C，M=Fe、Co等）是最有发展前景的非贵金属电催化剂之一，其性能依赖于催化剂表面的活性物种密度.通过常规的热解含氮前驱物与金属盐的方法制得的催化剂往往存在金属活性物种被包埋而不能有效利用的缺点.考虑到石墨相氮化碳（g-C₃N₄）富含类吡啶氮和亚纳米孔腔结构，将g-C₃N₄包覆在高导电性碳纳米笼（hCNC）表面，进而利用表层g-C₃N₄的配位和限域作用锚定大量Co²⁺离子，获得的Co/g-C₃N₄/hCNC复合物经热解后形成了活性位高度暴露、导电性好、孔结构丰富的Co/N/C催化剂.800℃热解得到的最优化催化剂在碱性介质中展现出优异氧还原活性，其起始电位（0.97 V）与商业Pt/C催化剂相当，且抗甲醇干扰性能和稳定性优异.此项研究提供了一种构建具有高度暴露活性位的M/N/C催化剂的有效策略.