Mesoporous SiO2 produced by mineralization of yeast cells as an efficient electrocatalyst for oxygen reduction reaction

Mes oporous SiO2 (yeast-SiO2/C) was successfully prepared by mineralization of yeast cell template under different pH values. Analysis of the nitrogen adsorption-desorption isotherms indicated that the pore size distribution of the mesoporous yeast-SiO2 samples significantly varies depending on the pH value used f or biomineralization. Average pore diameters for the samples synthesized at pH 5.0, 7.0, and 11.0 were found to be 7.9, 17.8, and 9.4 nm, respectively. The mineralization ability of silicon ions can be enhanced using conditions with a higher acidity. The air electrodes fabricated using the yeast-SiO2 mesoporous composites exhibited remarkable electrocatalytic activity in oxygen reduction reaction under alkaline conditions. The mesoporous sample synthesized at pH 5.0 showed the highest electrocatalytic performance in the oxygen reduction reaction; this sample has the largest surface area and the highest total pore volume. It is supposed that the mesoporous structure of the nanocomposites predetermined by the yeast cell template significantly reduced the electrochemical polarization and improved mass transport in the air diffusion electrode.