Citrate-Stabilized Gold Nanoparticles as High-Performance Electrocatalysts: The Role of Size in the Electroreduction of Oxygen

Fuel cells stand out as among the most promising alternatives for non-sustainable fossil fuel based economy. Efficient electrocatalysts for the oxygen reduction reaction (ORR) are required for the mass application of fuel cells. Citrate-stabilized gold nanoparticles (AuNPs) are proposed as potentialdependent electrocatalysts for the ORR. AuNPs were synthesized by a green, reproducible, and easy scale-up method. After exhaustive characterization, the electrocatalytic activity of the resulting AuNPs was investigated in alkaline media. Static and dynamic electrochemical studies showed a core-size dependent tendency both for their potentials and intensities. For the first time ever, the hysteresis effect in the ORR profile over Au nanoelectrocatalysts is reported herein. In addition, the electrocatalytic efficiency was comparable to those obtained for Au clusters, suggesting the benefits of the citrate stabilizing agent on the electrocatalyst performance of nanomaterials based on noble metals for ORR. These results pave the way for the design of non-coated AuNPs as strong candidates for ORR