Exoelectrogenic biofilm as a template for sustainable formation of a catalytic mesoporous structure

Abstract

Mesoporous structures can increase catalytic activity by maximizing the ratio of surface area to volume, but current synthesis techniques utilize expensive polymers and toxic chemicals. A Geobacter sulfurreducens biofilm was used as a sustainable template to form mesoporous Pd structures while eliminating the need for synthetic chemicals. The bulk of the biofilm material was removed by thermal treatments after nanoparticle formation, producing a catalytic Pd mesoporous (pore size 9.7 AE 0.1 nm) structure attached to the graphite electrode with a 1.5-2 mm thick backbone composed of nanoparticles ($200 nm). A control electrode electrochemically plated with Pd in the absence of a biofilm exhibited a variable planar Pd base ($0.5-3 mm thick) with sporadic Pd extrusions ($2 mm across, 1-5 mm tall) from the surface. The biotemplated mesoporous structure produced 15-20% higher stable current densities during H 2 oxidation tests than the electrochemically plated control electrode, even though 30% less Pd was present in the biotemplated catalyst. These results indicate that electroactive biofilms can be used as a sustainable base material to produce nanoporous structures without the need for synthetic polymers.

Potential regulates metabolism and extracellular respiration of electroactive Geobacter biofilm

“…Geobacter sulfurreducens is one of the most abundant redox‐active organisms in sediments, soils, and anaerobic sludge and is an important model strain in environmental and electrochemical applications (Lovley et al, ; TerAvest & Ajo‐Franklin, ; Yates, Cusick, Ivanov, & Logan, ). First isolated as a dissimilatory metal reducer, G. sulfurreducens can extracellularly reduce and dissolve solid Fe(III) oxides and MnO 2 in the environment to support the respiration (Caccavo et al, ; Mehta, Coppi, Childers, & Lovley, ) and thus is involved in the redox cycles of iron and manganese.…”

Microbial synthesis of Pd/Fe3O4, Au/Fe3O4 and PdAu/Fe3O4 nanocomposites for catalytic reduction of nitroaromatic compounds

“…However, the negative and toxic effects of the “metal armor” on normal metabolism and proliferation activities of microbial cells may hinder the long-term or repeated using of these palladized cells. On the other hand, some researchers removed Shewanella and other bacterial cells after biosynthesis processes through calcination or pyrolysis and made use of the biotemplated nanoparticles in a purely chemical or electrochemical way 13 14 15 .…”

Activating electrochemical catalytic activity of bio-palladium by hybridizing with carbon nanotube as “e− Bridge”

“…In order to overcome the poor conductivity of biomaterial-metal NPs complex, strategy by using high temperature to carbonize the biomaterials has been extensively employed 26 – 29 . However, this method requires additional energy consumption and may lead to the aggregation of NPs, resulting in the decease of specific surface area and decline the catalytic activity 19 , 26 .…”

“…In order to overcome the poor conductivity of biomaterial-metal NPs complex, strategy by using high temperature to carbonize the biomaterials has been extensively employed 26 – 29 . However, this method requires additional energy consumption and may lead to the aggregation of NPs, resulting in the decease of specific surface area and decline the catalytic activity 19 , 26 . Additionally, to avoid carbonized biomass blocking the active sites of metal NPs, oxygen had to be introduced to remove excessive carbon 26 , which could increase the chance of forming less-conductive metal oxide layer and may attenuate the electrochemical activity 20 , 30 .…”