Transition-metal and nitrogen-codoped carbon-based (TM-N/C) catalysts are promising candidates for catalyzing the oxygen reduction reaction (ORR). However, TM-N/C catalysts suffer from insufficient ORR activity, unclear active site structure, and poor durability, particularly in acidic solution. Herein, we report single Co atom and N codoped carbon nanofibers (Co–N/CNFs) catalyst with high durability and desirable ORR activity in both acidic and alkaline solutions. The half-wave potential of the ORR shows a negligible decrease after a 10 000-cycle accelerated durability test. The high ORR durability is originated from the structural stability of the atomically dispersed Co-based active site, as revealed by probing analysis and density functional theory calculations. A passive direct methanol fuel cell with the Co–N/CNFs cathode delivers a maximal power density of 16 mW cm–2 and a remarkable stability during a 200 h test, demonstrating the application potential of Co–N/CNFs. The breakthrough of the highly durable TM-N/C ORR catalyst could open an avenue for affordable and durable fuel cells.
Abstract Single-site catalysts feature high catalytic activity but their facile construction and durable utilization are highly challenging. Herein, we report a simple impregnation-adsorption method to construct platinum single-site catalysts by synergic micropore trapping and nitrogen anchoring on hierarchical nitrogen-doped carbon nanocages. The optimal catalyst exhibits a record-high electrocatalytic hydrogen evolution performance with low overpotential, high mass activity and long stability, much superior to the platinum-based catalysts to date. Theoretical simulations and experiments reveal that the micropores with edge-nitrogen-dopants favor the formation of isolated platinum atoms by the micropore trapping and nitrogen anchoring of [PtCl 6 ] 2- , followed by the spontaneous dechlorination. The platinum-nitrogen bonds are more stable than the platinum-carbon ones in the presence of adsorbed hydrogen atoms, leading to the superior hydrogen evolution stability of platinum single-atoms on nitrogen-doped carbon. This method has been successfully applied to construct the single-site catalysts of other precious metals such as palladium, gold and iridium.
Proton exchange membrane fuel cells are promising candidates for a clean and efficient energy conversion in the future, the development of carbon based inexpensive non-precious metal ORR catalyst has becoming one of the most attractive topics in fuel cell field. Herein we report a Fe- and N- doped carbon catalyst Fe-PANI/C-Mela with graphene structure and the surface area up to 702 m2 g−1. In 0.1 M HClO4 electrolyte, the ORR onset potential for the catalyst is high up to 0.98 V and the half-wave potential is only 60 mV less than that of the Pt/C catalyst (Loadings: 51 μg Pt cm−2). The catalyst shows high stability after 10,000 cyclic voltammetry cycles. A membrane electrode assembly made with the catalyst as a cathode is tested in a H2-air single cell, the maximum power density reached ~0.33 W cm2 at 0.47 V.
Biological methods for nanoparticle synthesis are gaining increasing recognition due to their ability to enhance the biocompatibility of nanoparticles for biomedical and environmental applications. Surface modification via biotechnology to improve the biocompatibility of nanoparticles is an effective strategy. In this study, the synthesis of biosurfactant-silver nanoparticles (BS32-AgNPs) was mediated by lipopeptide biosurfactant as capping agents and stabilizers. The antimicrobial mechanisms and antibacterial properties of BS32-AgNPs were also explored. The results showed that the average particle size of BS32-AgNPs was 26 nm, exhibiting a face-centered cubic structural characteristic and high stability and dispersibility, with a Zeta potential value of –51.4 mV. BS32-AgNPs demonstrated significant antimicrobial activity, with minimum inhibitory concentration of 7.5 mg/l and 15 mg/l against E. coli DH5α (G-) and B. borstelensis (G+), respectively. Scanning electron microscope and transmission electron microscopy observations revealed that the antimicrobial mechanism of BS32-AgNPs involves adsorption onto the bacterial surface, interacting with the cell membrane, increasing membrane permeability, and ultimately leading to membrane disruption and cell death. Further experimental evaluation of the antimicrobial activity of BS32-AgNPs against sulfate-reducing bacteria (SRB) showed that at a concentration of 120 mg/l, the functional genes dsrB and aprA of encoding SRB accounted for nearly 0% of the total bacterial population, which demonstrates the stable and potent antimicrobial activity of BS32-AgNPs. Moreover, it provides a green and efficient new method for the suppression of SRB in oil reservoir environments.
吕金钊 a 胡仁之 a 卓欧 a 许波连 a 杨立军 a 吴强 a 王喜章 * ,a,b 范以宁 a 胡征 a,b ( a 介观化学教育部重点实验室 南京大学化学化工学院 南京 210093) ( b 南京大学(苏州)高新技术研究院 苏州 215123) 摘要 以碳氮纳米管(NCNTs)为载体, 利用氮的锚定作用, 采用三种不同的制备方法(等体积浸渍法、胶体法和沉积沉 淀法)方便地构建了负载铁物种的 Fe/NCNTs 催化剂.系统考察了制备方法对催化剂的结构及费托反应性能的影响.结 果表明, 制备方法影响铁纳米粒子的粒度和分布、催化剂的还原和碳化行为, 使催化剂表现出不同的催化性能.等体积 浸渍法得到分散性较好、粒径小和分布窄[(8±4) nm]、容易还原和碳化的催化剂, 反应中呈现出最高的低碳烯烃选择
Two phenothiazine derivatives and a Cd-MOF ( Cd-PTZ-db ) were synthesised and investigated for their anti-Kasha’s rule emissions in solid state. Cd-PTZ-db can be further applied for the detection of ClO − (hypochlorite).
The application of layered double hydroxides (LDHs) in supercapacitors is encouraged by their high capacitances but still limited by deficient cycling stability. The remarkable capacitance decay of LDHs during cycling mainly results from the narrowing of the interlayer distance due to the interlayer anion replacement. A polymer encapsulation strategy is developed to improve the cycling stability of LDHs by inhibiting the anion exchange, opening a new avenue to develop stable LDH-based supercapacitor materials.
Pd nanoflowers (Pd-NF) composed of ultrathin Pd nanosheets show significantly enhanced activity towards the electro-oxidation of formic acid compared to ordinary Pd nanoparticles.
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