Microbial synthesis of highly dispersed nano-Pd electrocatalyst for oxygen reduction reaction

Microbial fabrication is eco-friendly for nobel-metal catalysts typically used in proton ex-change membrane fuel cell (PEMFC). In our study, nano-Pd electrocatalysts were suc-cessfully prepared by using three Shewanellas as precursors through hydrogen reduction (200 degrees C) and carbonization (800 degrees C). The analysis revealed that the catalysts showed outstanding ORR electrocatalytic performance via a predominant four-electron oxygen reduction pathway in alkaline medium. The best performance was obtained for Pd/HNC-32, which showed a mass activity at 0.526 A mg(-1), 3.78 times higher than that of com-mercial Pd/C. Shewanella putrefaciens CN-32 was a more effective Pd-adsorbent. The enhanced performance can be ascribed to the small Pd-particle size and uniform disper-sion on microbial support, which results from stronger hydrophilicity of Shewanella putre-faciens CN-32. The content of nitrogen is another key to the performance of Pd/HNC-32. This study developed a promising strategy for screening microbial strains for electro-catalyst fabrication. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.