Photo-bioelectrochemical system for harnessing solar energy.

Abstract

Cyanobacteria possess unique and exciting features among photosynthetic microorganisms for energy conversion applications. This thesis project focuses on conversion of solar energy into photocurrent generation comparing three different strains of Cyanobacteria, Leptolyngbia sp. from New Zealand (CYN82), Leptolyngbia sp. from Antarctica (CYN65), Chroococcales sp. from Antarctica (CYN67) and one eukaryotic organism, Paulschulzia pseudovolvox from Lake Tikitapu, New Zealand (UKE). By illuminating with light (intensity 400 W/m2) each bacterium (immobilized on a graphite electrodes in mediated electron transfer conditions) a photocurrent is generated through the extraction of electrons from water photolysis.
Different mediators were explored: two soluble mediators 0.5 mM para-benzoquinone (pBQ) and 0.5 mM ferricyanide solution dissolved in buffer, a redox polymeric mediator Os(bpy)2Cl complexed with poly(1-vinylimidazole) and a combination of pBQ and Os-polymer. The photocurrent values from chronoamperometric experiments were collected and compared. The maximum currents density was 47.167 μA•cm-2 from CYN67 using a double mediator system.
Further investigations on CYN67 in different buffer concentrations, pBQ concentrations and light intensity conditions showed that the best electrogenic activity for this cyanobacterium yields a current density of 58.368 μA•cm-2.

Popular Abstract

According to current projections the global population will reach 9 billion people by the year of 2050 and this population will need to be supplied with energy. Todays we strongly depend on non-renewable energy sources with all their related problems of scarcity and environmental impact. Several alternative energy sources have been developed and solar energy is one of the best candidates, because it is the most accessible and abundant renewable energy source available to us. A steadily improving understanding of natural photosynthesis at the molecular level has inspired researchers to develop systems that mimic (or use) natural photosynthesis to convert solar energy to fuel.
In nature, the process, which converts solar energy into chemical energy, is called photosynthesis. This chemical energy is stored as carbohydrate molecules, which are synthesized from water and carbon dioxide. The process takes place in cyanobacteria, algae and higher plants in the presence of sun light.
This study focused on the imitation of photosynthesis for energy production. As biological material different cyanobacterial strains and algae were used. By illuminating graphite electrodes modified with cyanobacteria or algae, photocurrent densities were detected and compared. This was done in the presence of substances, so-called mediators, which act as electron shuttles and help the electron transfer between the cells and the electrode. Various experimental conditions, such as light intensity, ionic strength, mediator concentration, were also tested. Through the use of a pesticide, diuron, that blocks the photosynthetic system, these microorganisms were confirmed to be the source of the registeted photo current.

• author: Grippo, Valentina
• supervisor: Lo Gorton
• organization: Department of Chemistry
• course: KEMR16 20141
• year: 2014
• type: H2 - Master's Degree (Two Years)
• subject: Chemistry
• keywords: analytisk kemi, analytical chemistry
• language: English
• id: 4780425
• date added to LUP: 2014-11-18 15:42:12
• date last changed: 2014-11-18 15:42:12