Active and Stable Oxygen Reduction Catalysts Prepared by Electrodeposition of Platinum on Mo2C at Low Overpotential

Decreasing the cost and improving the durability of polymer electrolyte membrane fuel cell (PEMFC) electrodes are two major unresolved challenges. Electrodeposition of low-dimensional Pt on transition metal carbide supports could be a way to simultaneously address both issues. Synthesis of low-dimensional Pt typically requires expensive equipment or techniques that are difficult to reproduce or scale. An electrodeposition-based technique to accomplish this goal is therefore highly desirable. The strong adhesion energy between Pt and the C sites on the alpha-Mo2C surface suggests that an electrochemical technique could be exploited for this purpose. Here, PtCl62- was electrodeposited onto an alpha-Mo2C support at low and high overpotentials (eta). A dramatic increase in the electrochemical surface area and the mass activity of the oxygen reduction reaction (ORR) was observed when Pt was deposited at low overpotentials (+8 and +18 mV vs SCE) as compared to high overpotentials (-67 and -92 mV vs SCE). Indeed, catalysts prepared in the low-overpotential region achieved an ORR mass activity of 275 A/g(Pt) and broke the linear relationship between mass activity and loading typically exhibited by these materials. Furthermore, catalysts prepared in the low-overpotential region exhibited superior stability out to 5000 cycles in an accelerated stress test (AST) as compared to samples prepared at higher overpotentials or by chemical reduction of Pt onto alpha-Mo2C and carbon supports.

Automated summary

This study focused on the electrodeposition of low-dimensional Pt on transition metal carbide supports for improved durability and cost reduction of PEMFC electrodes. The low-overpotential region achieved a high ORR mass activity of 275 A/g(Pt) and superior stability compared to samples prepared at higher overpotentials.