Strontium manganese-based bimetallic oxide cathode catalyst for enhanced power production and desalination in microbial desalination cell

The growing water demand supports the innovation of desalination technologies. Microbial desalination cell (MDC), a form of bio-electrochemical system, provides a green solution for saltwater desalination with its bio-energy harvesting property while treating wastewater through exo-electrogens. The use of suitable catalysts further enhances the power production and desalination efficiency of MDC by overcoming the slack kinetics of oxygen reduction reaction (ORR). A bimetallic oxide of Sr-Mn was thus prepared by the co-precipitation method and coated on the cathode surface to improve the performance of MDC. This bimetallic oxide obtained had a significant amount of perovskite (SrMnO₃) synthesized in the process, contributing to the enhanced catalytic activity. The physicochemical properties of the catalyst were characterized through scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy analysis. The electrochemical characterization was done through cyclic voltammetry and electrochemical impedance spectroscopy analyses, showcasing the superior performance of the synthesized catalyst. The MDC having bimetallic oxide-coated cathode performed better than the MDC having bare carbon felt cathode due to improved ORR within the system. The desalination chamber was supplied with NaCl concentrations from 10 g/L to 25 g/L following consecutive cycles in a fed-batch mode. The maximum average chemical oxygen demand (COD) removal efficiency was recorded as 81.2 ± 0.1 %, and desalination efficiency of 92 ± 0.18 % with a maximum open circuit voltage of 909 mV. Thus, advocating the use of bimetallic oxide of (Sr-Mn) as a suitable cathode catalyst, which is effectively promoting the performance of MDC for real-life applications.