Enhancing the performance of microbial desalination cells using δMnO2/graphene nanocomposite as a cathode catalyst

In this work, δMnO2 was anchored into graphene nanosheets via a mediated simple and eco-friendly approach to be used as a potential low-cost cathodic catalyst in microbial desalination cells (MDC). MnO2/G based MDC revealed a faster start-up and stable performance during the operation compared with the catalyst-free control MDC. The average chemical oxygen demand (COD) removal efficiencies were 85.11 ± 5.13 and 86.20 ± 4.85% and average columbic efficiencies throughout the operation cycles were 1.52 ± 0.32% and 0.70 ± 0.35% for MnO2/G based reactor and control reactor, respectively. The average desalination efficiencies were 15.67 ± 3.32 and 13.21 ± 2.61% for MnO2/G based reactor and control reactor, respectively. The superior catalytic performance of MnO2/G based cathode improved current generation which is the key desalination stimulus. MnO2/G based reactor revealed a lower internal resistance of 430 Ω compared with 485 Ω for the catalyst-free control reactor and, similarly, the maximum power densities were found to be 12.5 and 6.5 mW/m2, respectively. MnO2/G catalyst offered an improved MDC performance, however, still with uncompetitive performance in comparison with platinum group metals catalysts.