Synthesis\nof Palladium Nanoparticles by Electrode-Respiring Geobacter\nsulfurreducens Biofilms

Electroactive microorganisms\nsuch as Geobacter sulfurreducens can\ncouple organic electron donor oxidation to the respiration of\nelectrode surfaces, colonizing them in the process. These microbes\ncan also reduce soluble metal ions, such as soluble Pd, resulting\nin metallic nanoparticle (NP) synthesis. Such NPs are valuable catalysts\nfor industrially relevant chemical production; however, their chemical\nand solid-state syntheses are often energy-intensive and result in\nhazardous byproducts. Utilizing electroactive microbes for precious\nmetal NP synthesis has the advantage of operating under more sustainable\nconditions. By combining G. sulfurreducens’s ability to colonize electrodes and synthesize NPs, we performed\nelectrode cultivation ahead of biogenic Pd NP synthesis for the self-assembled\nfabrication of a cell-Pd biomaterial. G. sulfurreducens biofilms were grown in electrochemical reactors with added soluble\nPd, and electrochemistry, spectroscopy, and electron microscopy were\nused to confirm (1) metabolic current production before and after\nPd addition, (2) simultaneous electrode respiration and soluble Pd\nreduction over time, and (3) biofilm-localized Pd NP synthesis. Utilizing\nelectroactive microbes for the controlled synthesis of NPs can enable\nthe self-assembly of novel cell-nanoparticle biomaterials with unique\nelectron transport and catalytic properties.