This Small Business Innovation Research Phase I project will focus on the development of a novel MnO2 cathode catalyst for power generation and wastewater treatment in microbial fuel cells (MFCs); an emerging biotechnology for generation of electricity from wastewater treatment facilities. Currently, development of MFCs is impeded by the cathode reaction, which is the rate-limiting step in MFCs. Current cathode material is platinum based, which is costly and relatively scarce. Fouling of the cathode decreases the cathode effectiveness and increases maintenance costs. A MnO2-cathode catalyst will be developed to enhance the cathode reaction rate, reduce costs, and minimize fouling. The catalyst will incorporate metal additives to enhance the reaction, have an anti-fouling coating to minimize fouling, and be prepared as a monolithic material. The developed cathode will be tested in laboratory-scale systems and a continuous-flow pilot-scale MFC system treating actual wastewater from a wastewater treatment plant.
The broader/commercial impact of this project will be the removal of a key hurdle that has impeded commercialization of MFCs. A lower cost and more effective catalyst is a key component for bringing MFC technology to a cost that will be commercially attractive to any wastewater treatment facility. The anaerobic MFC has the advantage over an aerobic process due to less power consumption and reduced sludge volume. The initial cost of the MFC and the maintenance would be offset by the reduction of electricity consumed from the power grid. The development of a cost-effective MFC system has the potential for significant impact on energy and environmental sustainability and could eventually lead to for self-sustainable wastewater treatment plant.
. MFCs are an emerging biotechnology to generate electricity from wastewater treatment. Currently, development of MFCs is impeded in part by the cathode reaction. Current cathode material is platinum based, which is costly and relatively scarce. A low-cost, metal-oxide cathode was developed to enhance the cathode reaction rate, reduce costs, and minimize fouling. The catalyst had select metals added to enhance the reaction, was prepared as a monolithic material to simplify the design, and had a coating applied to minimize fouling. The developed cathode was tested in laboratory-scale systems. 2. Research Plan: Experimental Methods, Responsibilities, and Goals The research was performed according to the five tasks outlined below. Tasks 1 through 4 were completed successfully. Task 5 was not completed due to technical problems. Task 1: Catalyst Synthesis with Single/Multiple Element Additives Task 2: Monolithic Material Synthesis Task 3: Antifouling Coating Task 4: Laboratory-scale MFC Tests Task 5: Pilot-scale MFC Tests The key finding from this work is that the power density corresponds best with the conductivity of the material – the higher conductivity materials showed the highest power density. This shows that conductivity is the most important property investigated in this work. This result will allow focus on future work on increasing the conductivity of the material to improve cathode performance. 3. Research Results Summary The data generated during the Phase 1 activities was successful and provides numerous avenues that could be investigated in future research. The metal oxide materials were successfully synthesized as determined by various characterization techniques. The best material prepared and tested here had a maximum power density that was comparable to platinum, which is the current industry standard. This alone will decrease the cost of energy production and make this technology more attractive to the end user. This will also allow for more regular replacement of the cathode, which will reduce the effects of fouling and keep power generation closer to optimal. The monolithic materials had some technical problems. There was deterioration and breaking of the monolithic material during testing that could have caused measurement problems and high uncertainty. A maximum power density was produced for the coated monolithic material, suggesting that the coating helped hold the material together longer to enable this measurement. The particulate material had higher power densities. This could be because the active sites of the catalyst are not exposed in the monolithic material. In the monolithic framework, the active sites might not be exposed because the crystals are a collection of long tube-like structures where the majority of the exposed surface is the outer shell of the tube. This is similar to a box of round toothpicks with flat ends. If the active site is the flat end of the toothpick, then short broken pieces will expose more active sites. It was found with the coated monolith that the coating did not make the material inactive, as a power density data point was able to be obtained. The monolithic K–OMS-2 cathode MFC system seems functional, but needs further strength optimization and testing to conclude its feasibility as a new cathode system. The key finding from this work is that the power density corresponds best with the conductivity of the material. This shows that conductivity is the most important property investigated in this work. This result will allow future work to focus on increasing the conductivity of the material to improve cathode performance.
