Ionomers From Kraft Lignin for Renewable Energy Applications
Ionomers From Kraft Lignin for Renewable Energy Applications
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DOI：
10.3389/fchem.2020.00690
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发表时间：
2020-08-26
影响因子：
5.5
通讯作者：
Dishari, Shudipto K.
中科院分区：
文献类型：
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作者：
Farzin, Seefat;Johnson, Tyler J.;Dishari, Shudipto K.
将工业/农业富含木质素的废物转化为用于电化学装置（例如，燃料电池）可以有助于生物和能量经济。燃料电池的主要限制是在电极上的类似于2-30-nm厚的基于离子传导聚合物（离聚物）的催化剂-粘合剂层内的弱离子传导性。在这里，我们战略性地磺化硫酸盐木质素（纸浆和造纸工业的副产品）设计具有不同离子交换容量（IEC）（LS x; x = IEC）的离聚物，可以潜在地克服这种界面离子传导限制。我们测量了离子电导率，吸水率，离子域特性，密度，并预测了水的流动性/刚度的Nafion，LS 1.6，和LS 3.1在亚微米厚的水合膜。LS 1.6的离子电导率高于Nafion和LS 3.1在具有类似厚度的膜的数量级。这些膜的离子电导率与它们的吸水率和IEC不相关。在LS 1.6大分子的三维、较低密度的支化结构内，-SO 3 H和-OH基团非常接近，这可能促进了具有高度移动的水分子的较大离子域的形成。与LS 1.6相比，LS 3.1在干燥状态下显示出更高的玻璃化转变温度和膜刚度，这在加湿期间持续。相反，Nafion在加湿后显著硬化。因此，刚性LS 3.1和Nafion膜内的较小离子簇导致离子电导率低于LS 1.6。由于LS x离聚物（与商业木质素磺酸盐不同）不溶于水，因此它们适用于亚微米厚膜中的低温水介导离子传导。
Converting industrial/agricultural lignin-rich wastes to efficient, cost-effective materials for electrochemical devices (e.g., fuel cells) can aid in both bio- and energy economy. A major limitation of fuel cells is the weak ion conductivity within the similar to 2-30-nm thick, ion-conducting polymer (ionomer)-based catalyst-binder layer over electrodes. Here, we strategically sulfonated kraft lignin (a by-product of pulp and paper industries) to design ionomers with varied ion exchange capacities (IECs) (LS x; x = IEC) that can potentially overcome this interfacial ion conduction limitation. We measured the ion conductivity, water uptake, ionic domain characteristics, density, and predicted the water mobility/stiffness of Nafion, LS 1.6, and LS 3.1 in submicron-thick hydrated films. LS 1.6 showed ion conductivity an order of magnitude higher than Nafion and LS 3.1 in films with similar thickness. The ion conductivity of these films was not correlated to their water uptake and IECs. Within the three-dimensional, less dense, branched architecture of LS 1.6 macromolecules, the -SO3H and -OH groups are in close proximity, which likely facilitated the formation of larger ionic domains having highly mobile water molecules. As compared to LS 1.6, LS 3.1 showed a higher glass transition temperature and film stiffness at dry state, which sustained during humidification. On the contrary, Nafion stiffened significantly upon humidification. The smaller ionic cluster within stiff LS 3.1 and Nafion films thus led to ion conductivity lower than LS 1.6. Since LS x ionomers (unlike commercial lignosulfonate) are not water soluble, they are suitable for low-temperature, water-mediated ion conduction in submicron-thick films.