Co-Fe普鲁士蓝(CoPBA)是目前被广泛研究的超级电容器正极材料,其比电容高循环性能好,但低导电性和较差的倍率性能限制了其在超级电容器中的应用.为了提高CoPBA的导电性和电化学性能,本文以Co-glycerate为前驱体,采用牺牲模板法制备了 Co-Fe普鲁士蓝/多壁碳纳米管(CoPBA/MWCNT)复合材料,利用XRD、SEM和FTIR等对复合材料的结构和形貌进行表征,使用电化学工作站在三电极体系和非对称超级电容器中测定了复合材料的电化学性能.实验结果表明:采用牺牲模板法成功合成出形貌较好的球状复合材料,以中性溶液Na2SO4为电解液,测得在1 A/g的电流密度下复合材料的质量比电容达到391.5 F/g.在10 A/g的高电流密度下比电容达到312.6 F/g,为1 A/g时的79.8％.利用软件模拟得出电荷转移电阻由3.9 Ω降低到1.1 Ω.以CoPBA/MWCNT为正极,以活性炭为负极制成非对称电容器,在功率密度为1092 W/kg时能量密度可达39.5 Wh/kg,5 000次循环后容量保持率为85.2％.采用牺牲模板法制备的CoPBA/MWCNT,其电容、导电性和倍率性能均有提高,并具有较高的实际应用价值.

Cobalt hexacyanoferrate (CoHCF) as a promising cathode material of asymmetrical supercapacitors gen-erally undergoes a single redox reaction of Fe(II)/Fe(III) couple to store energy in neutral aqueous elec-trolytes. Its framework Co ions are electrochemically inactivated, leading to a limited electrochemical capacity. Herein, we develop a strategy to activate the reversible Co(II)/Co(III) redox reaction through tuning the microenvironment of Co ions. A carbon nanodots/CoHCF (C-dots/CoHCF) hybrid nanostructure has been successfully fabricated via a simple co-precipitation reaction of Co2+ and [Fe(CN)(6)](3-) ions in the presence of carboxylate-rich C-dots. Impressively, electrochemical results and X-Ray photoelectron spectroscopy (XPS) reveal the charge storage of C-dots/CoHCFs due to two-specie (Fe and Co) redox reactions, which render an enhanced electrochemical capacity. It is considered that the activation of reversible Co(II)/Co(III) redox reaction is due to the strong coordination interaction between the terminated framework Co ions and carboxylate groups of C-dots. In addition, this nanostructure offers increased active sites and promotes electron conductivity, thereby achieving a remarkable high specific capacitance (394 F g(-1) at 1 A g(-1)) and excellent rate performance. The C-dots/CoHCF cathode is paired with an activated carbon anode to assemble an aqueous asymmetrical supercapacitor, which can deliver a high energy density of 48.6 Wh kg(-1) (488 W kg(-1)) and retain 88.3% of its initial capacitance over 5000 charge/discharge cycles. (C) 2021 Elsevier B.V. All rights reserved.

Co类普鲁士蓝(CoPBA)作为令人瞩目的超级电容器阳极材料拥有高比容量和优异的循环稳定性,但较差的电子导电性限制了其倍率性能.利用ZIF-67作为前驱体合成了Co类普鲁士蓝/多壁碳纳米管(CoPBA/MWCNT)复合材料,并使用XRD、SEM和TEM对材料的结构和形貌进行表征.在三电极体系中,测得CoPBA/MWCNT电极在电流密度为1 A·g?1时电容提高到312 F·g?1.制备的CoPBA/MWCNT电极有利于提高材料电导率和机械稳定性,从而获得更高的电化学性能.将CoPBA/MWCNT正极和活性炭(AC)负极组装为非对称电池,测得5000圈循环后容量保留率为83.1％,循环稳定性优异.

开发可控的NiMoO4纳米结构合成方法是获得高性能赝电容器电极材料的关键.以Ni-MOF为前驱体,采用模板转化法合成NiMoO4纳米球,以改善其结构并提升电化学性能.采用XRD、FTIR和SEM对所制备的NiMoO4样品的结构和形貌进行表征,并通过氮气吸脱附表征了其孔径和比表面积.MOF衍生的NiMoO4纳米球由超薄的纳米片状结构组成,这为电解质的渗透提供了有利的路径.在1 mol/L KOH水溶液的三电极体系中测试样品的电化学性能.当电流密度为1 A·g-1时,比电容高达1116 F·g-1.NiMoO4纳米球具有高比电容和优异的倍率性能,这归功于其大的比表面积和高电导率.以NiMoO4样品为正极,活性炭(AC)为负极制备的非对称超级电容器具有长期循环稳定性,经4000次循环(5 A·g-1)后的容量保持率为84.6％.

Cobalt hexacyanoferrate (CoHCF) possessing high capacity as well as remarkable cycling stability is generally considered to store charge via the electrochemical reaction of Fe3+/Fe2+ redox couple and Co ions are electrochemically inactive because of the low decomposition voltage of water. In this work, we report an efficient approach to fabricate the MnO2 nanosheet (MnO2 NS) coated CoHCF with enhanced electrochemical performance. More importantly, the capacity contribution from the Co3+/Co2+ redox couple is verified in neutral aqueous electrolytes, leading to a new understanding of the charge storage mechanism of CoHCF. The CoHCF/MnO2 nanocomposite exhibits a specific capacitance of 385 F g(-1) (1 A g(-1) in 0.5 M Na2SO4 aqueous electrolyte. It is revealed that CoHCF/MnO2 undergoes the reversible electrochemical reactions of Co3+/Co2+, Fe3+/Fe2+ and Mn4+/Mn3+ redox couples to store charges. Furthermore, an asymmetrical supercapacitor is fabricated with utilizing CoHCF/MnO2 as the cathode and activated carbon as the anode. The device operates at a high cell voltage of 2.0 V and delivers an energy density of 37.6 Wh kg(-1) at a power density of 1.1 kW kg(-1) Excellent cycling stability is exhibited that 86% of the initial discharge capacitance is maintained after 5000 charge-discharge cycles.