Optimization of hollow Pt-Ni alloy bifunctional electrocatalysts via ethylene glycol/glycerol ratio in modified polyol process

초록

In this study, we synthesize nano-sized, hollow-structured PtNi alloy catalysts with high activity and durability in acidic environments for the oxygen reduction reactions (ORR) and hydrogen evolution reaction (HER) through a modified polyol process, which involved the addition of an extra reducing agent to the conventional polyol method. By incorporating glycerol, a high-viscosity solvent, we can control the viscosity of the reaction medium and reduce the particle size, thereby developing catalysts with maximum electrochemically active surface areas. In half-cell experiments, an optimized hollow PtNi catalyst exhibits outstanding performance, showing 3.89- and 1.21-times higher mass activities for the ORR and HER, respectively, compared to those of commercial Pt/C catalyst, thereby maximizing the Pt utilization efficiency with superior durability. Density functional theory calculations confirm these findings, showing that the PtNi alloy catalyst has lower energy barriers for the ORR and HER than a pure Pt catalyst, leading to their enhanced activity. In polymer electrolyte membrane fuel cell tests, the hollow PtNi catalyst shows a power output of 1.69 W cm-2, which is 1.3 times higher than that of commercial Pt/C catalyst, thereby demonstrating excellent performance.

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