Sustainable electricity production from seawater using Spirulina platensis microbial fuel cell catalyzed by silver nanoparticles-activated carbon composite prepared by a new modified photolysis method

A new and innovative microbial fuel cell of high energy conversion efficiency (with no heat emission or corrosion problems) was formulated using nanoparticles of dry biomass Spirulina platensis microalgae. High cell potential up to 1.0 V was obtained from this microbial fuel cell. The Spirulina platensis nanoparticles have been prepared using the top-down approach, then were sonicated to facilitate their digestion as a feedstock for the microorganisms in the seawater. The microorganisms in the polluted seawater at the deaerated anode chamber oxidized the organic matter producing electrons that transfer to the anode surface inside the microbial fuel cell via the microbial nanowires. These electrons (electric current) passed in the external circuit from the anode surface to the cathode surface. The microstructure of the bacterial biofilm on the anode surface was confirmed using the scanning electron microscope. The promising catalyst silver nanoparticles-activated carbon composite was prepared by a new modified photolysis method. The transmitting electron microscope micrograph of silver nanoparticles showed an average particle size of about 10 nm homogeneously loaded on the activated carbon matrix. The powder X-ray diffraction pattern of silver nanoparticles-activated carbon composite confirmed the formation of zero-valent metallic silver nanoparticles via the photoreduction of silver nitrate using low cost modified photolysis method. The composite efficiently catalyzed the slow oxygen reduction reaction at the cathode surface. The open cell potential of microbial fuel cell was 500 mV and 1000 mV and the corresponding power density up to 1.0 and 2.5 W. m−2 in the absence and the presence of silver nanoparticles-activated carbon composite, respectively. Both open-cell potential and the closed-cell potential were maximized in the presence of silver nanoparticles-activated carbon composite and remained unchanged for nearly one month of the cell operation.