铋纳米颗粒负载的氮掺杂石墨毡用于稳定高效的铁铬液流电池

Bismuth nanoparticles anchored on N-doped graphite felts to give stable and efficient iron-chromium redox flow batteries

铁铬氧化还原液流电池(ICRFB)是一种具有成本效益的可规模化储能系统,其利用资源丰富、低成本的铬和铁作为电解液的活性物质。然而,ICRFB存在Cr^(3+)/Cr^(2+)电化学活性低、负极易产生严重的析氢反应(HER)等问题。本文报道了一种简单的合成策略,即通过自聚合和湿化学还原方法结合煅烧处理,在氮掺杂石墨毡(GF)表面沉积了非晶态铋(Bi)纳米颗粒(NPs),其作为ICRFB的负极材料时可展示出高效的电化学性能。生成的BiNPs与H+形成中间体,极大地抑制了HER副反应。此外,Bi的引入和GF表面的N掺杂通过协同作用显著提高了Fe^(2+)/Fe^(3+)和Cr^(3+)/Cr^(2+)的电化学活性,降低了电荷传递电阻,提高了反应传质速率。在不同的电流密度下,经25次循环,库仑效率仍高达97.7%。在60.0 mA cm^(-2)电流密度下,能量效率达到85.8%,超过了许多其他报道的材料。循环100次后容量达到862.7 mAh/L,约为GF的5.3倍。

Iron-chromium redox flow batteries(ICRFBs)use abundant and inexpensive chromium and iron as the active sub-stances in the electrolyte and have great potential as a cost-effective and large-scale energy storage system.However,they are still plagued by several issues,such as the low electrochemical activity of Cr^(3+)/Cr^(2+)and the occurrence of the undesired hydrogen evolu-tion reaction(HER).We report the synthesis of amorphous bismuth(Bi)nanoparticles(NPs)immobilized on N-doped graphite felts(GFs)by a combined self-polymerization and wet-chemistry reduction strategy followed by annealing,which are used as the negat-ive electrodes for ICRFBs.The resulting Bi NPs react with H+to form intermediates and greatly inhibit the parasitic HER.In addi-tion,the combined effect of Bi and N dopants on the surface of GF dramatically increases the electrochemical activity of Fe^(2+)/Fe^(3+)and Cr^(3+)/Cr^(2+),reduces the charge transfer resistance,and increases the mass transfer rate compared to plain GF.At the optimum Bi/N ratio of 2,a high coulombic efficiency of up to 97.7%is maintained even for 25 cycles at different current densities,the energy effi-ciency reaches 85.8%at 60.0 mA cm^(-2),exceeding many other reported materials,and the capacity reaches 862.7 mAh L^(-1) after 100 cycles,which is about 5.3 times that of bare GF.