Electrocatalysts: Selectivity and utilization

Electrocatalyst is the medium where the electrochemical conversion of chemical energy into electrical energy takes place in fuel cells. The overall performance of fuel cells is mostly influenced by efficiency of the electrocatalyst. Selectivity and utilization are some of parameters that determine electrocatalyst efficiency. This chapter reviews selectivity and utilization of electrocatalysts used in proton exchange membrane fuel cell (PEMFC). There are various types of electrocatalysts used in fuel cells ranging from Pt on carbon support, Pt alloys, and transition metals. Identified factors affecting the selectivity and utilization are surface morphology, facet structure, ionomer/catalyst interaction, and chemical composition. This review revealed that the high (100) and (111) facets result in high oxygen reduction reaction (ORR) activity due to large surface area exposed for reaction. Porous catalyst support with catalyst particles deposited on exterior shortens local diffusion pathway, thereby increasing ORR activity. Addition of Ni and Fe to Pt/C (PtNiFe/C) increases performance while Cr (PtCr/C) and Mo (MoPtFe/C) increases stability. 2020 target mass activity of 440mAg−1 has been reached and almost doubled (e.g., 780mAg−1 obtained from MoFePt/C-H electrocatalyst) in laboratory scale but difficult to upscale. Thus, highlighting the need to optimize methods for synthesizing electrocatalysts.