Maunu Kuosa

Starch and Cellulose as Fuel Sources for Low Temperature Direct Mode Fuel Cells

This paper is a study about a direct mode fuel cell with a near-neutral-state and alkaline electrolytes. The aim of study was to develop a fuel cell, which operates directly by mixing the fuel with the electrolyte. This arrangement helps to avoid inserting membranes and additional bacterial cultures in fuel cell. The target is also to create a fuel cell with a ca- pacity of few mWcm -2 with the starch as a fuel. Also, glucose and sorbitol have been tested as fuel for the fuel cell.

Production of Glucose by Starch and Cellulose Acid Hydrolysis and its Use as a Fuel in Low-Temperature Direct-Mode Fuel Cells

The use of glucose, which is produced from the acid hydrolysis of starch and cellulose, is studied as a fuel in a low-temperature direct-mode fuel cell (LTDMFC) with an alkaline electrolyte. Glucose is regarded as being as good a fuel as bioethanol, because both the fuels give 2 electrons per molecule in the fuel cell without carbonisation problems. However, glucose can be produced with fewer processing stages from starch and cellulose than can bioethanol. In the LTDMFC the fuel and the electrolyte are mixed with each other and the fuel cell is equipped only with metal catalysts. Cellulose as a fuel is of great importance because the fuel for the energy production is not taken from food production. A description of an acid hydrolysis method for starch and cellulose is presented. Values for glucose concentrations in each hydrolysate are analysed by means of a chromatographic method. Each glucose hydrolysate was made alkaline by adding of potassium hydroxide before feed in the fuel cell. Polarisation curves were measured, and they were found to produce lower current density values when compared to earlier tests with pure glucose. The Coulombic efficiency of pure glucose electrochemical oxidation in LTDMFC, which was calculated from a ratio of detected current capacity (As) to the maximum current capacity with the release of two electrons per molecule, was also found to be very low. Concerning the hydrolysates, the glucose concentrations were found to have values that were too low when compared to the earlier tests with pure glucose in a concentration of 1 M. The further development demands for the system under consideration are indicated. The concentration of glucose in the hydrolysate is essential to achieve high enough current density values in the LTDMFC.

Direct-Mode Glucose Fuel Cells with Near-Neutral-State Electrolytes: Anode Electrode Studies with Different Catalysts and Electrolytes

In the present study, a direct-mode glucose fuel cell with a neutral-state and near-neutral-state aqueous electrolytes is studied. The near-neutral state electrolytes are important for two reasons. Firstly, the pH of the electrolytes would be near the pH of liquid in living cells. Secondly, the neutral electrolyte would enable good corrosion resistance of catalyst materials. Three different catalyst materials, i.e. Pt-Pd, Raney-Ni and Ni-porphyrin complex, are tested in an anode half-cell configuration with one neutral-state (battery water) and with two near-neutral-state aqueous electrolytes, i.e. modified Krebs-Ringer (K-R) and phosphate, both buffered to a pH value of 7.4. Pt-Pd catalyst in the aqueous K-R electrolyte maintains the negative voltage of the anode half cell with higher current densities that the nickel catalysts do. To estimate the operation of the direct-mode glucose fuel cell, the K-R electrolyte from the anode half-cell tests is tested also in the cathode half-cell with combined catalyst of cobalt porphyrin complex and of spinel. The open circuit voltages and polarisation curves are measured. Also, preliminary results and oxidation degrees of glucose in the tests are shown. Based on our half cell measurements, there are high development demands for the electro-catalysts, which could work efficiently in the near-neutral-state electrolytes.

The Progress in the Ongoing Development Work: Enhancement of Glucose Electro-Oxidation in Direct-Mode Fuel Cells - An Update

This study deals with the R&D regarding the direct glucose fuel cell with a capacity of increasing the power density with glucose as a fuel. The direct-mode fuel cell in which the fuel and the alkaline electrolyte are mixed with each other is tested at room temperature. The direct-mode fuel cell is exposed to an externally generated electromagnetic field with 4 GHz sine signals between electrodes to cause both the splitting of the fuel molecule and the electrochemical oxidation. As a result from the use of the higher frequency signals, a maximum current density of 15 mAcm-2 has been achieved with the total voltage of 0.5 V.