Pd Nanoparticles on Carbon Supports as Electrocatalysts for the Oxygen Reduction Reaction

The development of efficient catalysts for proton exchange membrane fuel cells (PEMFCs) is crucial for their commercial viability. This study introduces a method for synthesizing Pd nanoparticles on carbon supports as electrocatalysts using microbial synthesis, specifically employing the bacterium Shewanella oneidensis MR-1. The so-produced catalysts exhibit enhanced catalytic activity and stability for the oxygen reduction reaction (ORR). The microbial synthesis approach offers advantages, such as high purity, cost-effectiveness, and environmental friendliness. Additionally, the use of sodium alginate (SA) hydrogel in the synthesis process further improves the catalyst's performance due to its metal chelating properties. The resulting Pd/C electrocatalysts, especially those synthesized with a composite matrix of SA and CaCO3, demonstrate superior ORR performances outperforming that of commercial Pd/C catalysts. It was found that the composite substrate affected the palladium recovery rate, whose increasing palladium absorption, refined particle size, improved graphitization degree, and increasing pyridinic-N of the resultant catalyst synergistically enhanced the availability of active centers that eventually contributed to the superior ORR performances. This research paves the way for the development of high-performance and cost-effective catalysts for PEMFCs.