Shen Shuiyun, Cheng Xiaojing, Wang Chao, Yan Xiaohui, Ke Changchun, Yin Jiewei, Zhang Junliang
Institute of Fuel Cells, School of Mechanical Engineering, Shanghai Jiao Tong University, China.
Phys Chem Chem Phys. 2017 Oct 4;19(38):26221-26229. doi: 10.1039/c7cp04837h.
A drastic reduction of the Pt loading in the cathode catalyst layers (CCLs) of proton exchange membrane fuel cells (PEMFCs) is much desired. However, a decrease in Pt loading inevitably leads to an unexpected increase of local O transport resistance (r) and severely weakens the fuel cell performance, particularly at high current densities. Thus, it is both urgent and meaningful to explore the impacts of the operating conditions on r in CCLs and therefore to clarify the intrinsic mechanism. Herein, we systematically explore the influences of the operating conditions, in terms of the dry O mole fraction, the relative humidity, the operating pressure and the temperature on r using limiting current measurements combined with mathematical calculations. The results show that, in contrary to the established rules, r in CCLs of PEMFCs is aggravated when the dry O mole fraction or the operating pressure are increased. It is also experimentally found that r in CCLs is alleviated with the increase in the relative humidity or the operating temperature. Moreover, an adsorption controlled solution-diffusion model is proposed to illuminate the local O transport behavior in CCLs of PEMFCs, and it accounts for the influence of the dry O mole fraction on r in CCLs.
非常希望大幅降低质子交换膜燃料电池（PEMFC）阴极催化剂层（CCL）中的铂负载量。然而，铂负载量的降低不可避免地会导致局部氧传输阻力（r）意外增加，并严重削弱燃料电池性能，尤其是在高电流密度下。因此，探索操作条件对CCL中r的影响并进而阐明其内在机制既紧迫又有意义。在此，我们使用极限电流测量结合数学计算，系统地探索了操作条件（以干燥氧摩尔分数、相对湿度、操作压力和温度表示）对r的影响。结果表明，与既定规则相反，当干燥氧摩尔分数或操作压力增加时，PEMFC的CCL中的r会加剧。实验还发现，CCL中的r会随着相对湿度或操作温度的增加而减轻。此外，提出了一种吸附控制的溶液扩散模型来阐明PEMFC的CCL中的局部氧传输行为，并且该模型解释了干燥氧摩尔分数对CCL中r的影响。
