Microbial Desalination Cells with Efficient Platinum-Group-Metal-Free Cathode Catalysts

An iron-nitrogen-carbon-based catalyst was used at the cathode of a microbial desalination cell (MDC) and compared with platinum (Pt) and an activated carbon (AC) cathode. The Fe-NﰟC catalyst was prepared by using nicarbazin (NCB) as the organic precursor through a sacrificial support method (SSM). Rotating ring disk electrode (RRDE) experiments show that Fe-NCB had a higher electrocatalytic activity compared to AC and Pt. The utilization of Fe-NCB in the cathode substantially improved the performance output with an initial maximum power density of 49 ﰠ 2 mW cmﰟ2 in contrast to Pt and AC catalysts, which show lower values of 34 ﰠ 1 and 23.5 ﰠ 1.5 mW cmﰟ2, respectively. After
four cycles, Fe-NCB catalyst lost 15% of its initial performance, but still was 1.3 and 1.8 times more active than Pt and AC, respectively. Solution conductivity inside the desalination chamber (DC) decreased by 46–55 % with every cycle. The pH of the cathodic chamber and the DC increased to 10–11, owing to the production of OHﰟ during the oxygen reduction reaction and the migration of OHﰟ into the DC. Chemical organic demand decreased by 73–83% during each cycle. It was shown that Fe-NCB and Pt had a similar coulombic efficiency (CE) of 39ﰠ7% and 38ﰠ2%, whereas AC had lower CE (24ﰠ5%).