Department of Materials Science, Key Laboratory of Mobile Materials, MOE, and State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, PR China.
Sci Rep. 2013 Oct 18;3:2986. doi: 10.1038/srep02986.
Pseudocapacitance is commonly associated to the reversible redox reactions from electrode materials, but the enhancement in pseudocapacitance that only relies on electrode materials is limited. Here, we explore the possibility of enhancing pseudocapacitance through both Co(OH)₂/graphene nanosheets (GNS) electrode and K₃Fe(CN)₆ electrolyte. With a good conductivity and favoring electron transfer, GNS are hybridized with Co(OH)₂ to improve the pseudocapacitance of Co(OH)₂, including enhancing its rate capability and electrochemical stability. Adding K₃Fe(CN)₆ into KOH electrolyte further enhances the pseudocapacitance via both directly contributing pseudocapacitance to Co(OH)₂/GNS and promoting the electron gain and loss of Co ions. This novel Co(OH)₂/GNS-K₃Fe(CN)₆/KOH electrode system shows an ultrahigh specific capacitance of 7514 Fg⁻¹ at 16 Ag⁻¹ in mixed 1 M KOH and 0.08 M K₃Fe(CN)₆, more than 100% coulombic efficiency, and long-term cycling stability (the capacitance retention is 75% after 20000 continuous charge-discharge cycles in mixed 1 M KOH and 0.04 M K₃Fe(CN)₆.
赝电容通常与电极材料的可逆氧化还原反应有关，但仅依靠电极材料来提高赝电容的效果是有限的。在这里，我们探索了通过 Co(OH)₂/石墨烯纳米片（GNS）电极和 K₃Fe(CN)₆电解质来提高赝电容的可能性。GNS 具有良好的导电性和有利于电子转移的性质，与 Co(OH)₂ 杂交可以提高 Co(OH)₂ 的赝电容，包括提高其倍率性能和电化学稳定性。将 K₃Fe(CN)₆ 添加到 KOH 电解质中，通过直接为 Co(OH)₂/GNS 提供赝电容以及促进 Co 离子的得失电子，进一步提高了赝电容。这种新型的 Co(OH)₂/GNS-K₃Fe(CN)₆/KOH 电极系统在混合 1M KOH 和 0.08M K₃Fe(CN)₆ 中以 16Ag⁻¹ 的电流密度下表现出超高的比电容为 7514 Fg⁻¹，超过 100%的库仑效率和长期循环稳定性（在混合 1M KOH 和 0.04M K₃Fe(CN)₆ 中经过 20000 次连续充放电循环后，电容保持率为 75%）。
