Our laboratory is engaged in the development of three-dimensional (3D) catalyst layers aimed at reducing the cost of polymer electrolyte fuel cells (PEFCs). Previously, we improved the performance by increasing the ionomer-to-carbon (I/C) ratio, thereby relatively reducing the amount of platinum catalyst. However, this approach did not effectively reduce the actual amount of platinum catalyst because the increase in the I/C ratio was achieved by fixing the ionomer content. In addition, we examined catalyst layers in which the ionomer content was kept constant while varying the platinum loading to increase the I/C ratio. However, reducing the platinum content also decreased the carbon support, which serves as an electronic conductor, resulting in no improvement in performance. In this study, three types of catalyst layers were fabricated via an inkjet printing method by incorporating Ketjen Black as electron conductor into the catalyst layer. This approach allowed us to decrease the Pt-to-carbon (Pt/C) ratio while maintaining a constant I/C ratio. Electrochemical evaluations demonstrated that a 34% reduction in Pt loading in the catalyst layer yield performance equivalent to that of conventional layers. Furthermore, a comparative analysis of additional carbon sources indicated that Ketjen Black outperformed Vulcan Black due to its favorable pore structure and dispersibility. These properties contributed to mitigating oxygen transport limitations, thereby enhancing overall cell performance.
SUGIURA et al. (Wed,) studied this question.