Electrocatalytic and Protective Properties of Ruthenium-Derivatized Bacterial Biofilm on Electrodes and Photoelectrodes

Abstract

Conversion of carbon dioxide is a process of particular scientific interest in recent years, due to the need to reduce the level of this greenhouse gas in the atmosphere by its storage and reduction. Another profit of the CO2 reduction is the possibility of producing useful chemical compounds from such a widespread in the environment source of carbon. Electrochemical and photoelectrochemical reduction of carbon dioxide are optional methods of obtaining fuel materials from CO2. However, because of the molecule stability and by that, high overpotentials of its electroreduction, and moreover because of the competitive hydrogen evolution reaction – efficient and selective catalytic systems active in the CO2 conversion process are sought.There has been proposed a bioelectrocatalytic system for conversion of carbon dioxide, containing bacterial biofilm (of the species Yersinia enterocolitica) at the electrode surface. Biofilms are robust matrices, stable in a wide range of environmental conditions, able to operate at room temperature and under atmospheric pressure, and appear to be attractive for use in electrocatalytic processes. They easily create well developed three-dimensional structures on various types of surfaces, including diverse materials used in the construction of electrodes. Biofilms hydrated matrix allows the electrolyte ions to easily move at the electrocatalytic interface – as a result, biofilms resemble ion-conducting gel-type systems, supporting redox processes. The structure and properties of biofilms make it possible to immobilize catalytically active molecules in the microbial layer grown on the electrode surfaces, and therefore there has been proposed a catalytic system with the organometallic ruthenium (II) complex dispersed in the biological layer, active in the process of carbon dioxide conversion. Ruthenium (II) complex is immobilized in the biofilm matrix by successive modification of the liquid medium (Luria-Bertani medium) for culturing bacteria with a solution of this complex compound. In addition, a biological matrix is used (along with the ruthenium (II) complex molecules dispersed in its layer) as a protective coating, stabilizing the unstable p-type semiconductor – copper (I) oxide. The proposed catalytic system present activity in the photoelectrochemical reduction of carbon dioxide and stability under experimental conditions.