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

Abstract

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‐N−C 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±2 μW cm−2 in contrast to Pt and AC catalysts, which show lower values of 34±1 and 23.5±1.5 μW cm−2, 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 OH− during the oxygen reduction reaction and the migration of OH− 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 39±7 % and 38±2 %, whereas AC had lower CE (24±5 %).

Boosting Microbial Fuel Cell Performance by Combining with an External Supercapacitor: An Electrochemical Study

“…Despite enzymes such as laccase or bilirubin oxidases are the most active catalysts for ORR in neutral media, their elevated cost and low durability obstruct their utilization in large scale . Platinum is a very active catalyst, but it is extremely expensive and sensible to poisoning in the presence of anions . Carbonaceous‐based materials and transition metal‐containing catalysts have replaced platinum successfully.…”

“…[26] Platinum is a very active catalyst, but it is extremely expensive and sensible to poisoning in the presence of anions. [27][28][29][30] Carbonaceous-based materials [31][32][33] and transition metal-containing catalysts [34][35][36][37] have replaced platinum successfully. The addition of transition metals and especially FeÀ NÀ C active sites has improved significantly the performance almost doubling the MFCs output.…”

Oxygen Reduction Reaction Electrocatalysts Derived from Iron Salt and Benzimidazole and Aminobenzimidazole Precursors and Their Application in Microbial Fuel Cell Cathodes

“… 26 − 29 It is well-known that platinum is a rare and expensive metal, which can be easily poisoned in a polluted environment and consequently is not suitable for MFCs applications. 30 − 32 As a matter of fact, Pt was the most used catalyst in MFCs for several years however this choice was mainly dictated by the fact that Pt catalysts were heavily studied and used in acidic and alkaline fuel cells, technologies that are more mature compared to MFCs systems. 29 , 33 , 34 Pt has been recently substituted by materials that are potentially cost-effective and moreover are durable in harsh and contaminated environments.…”

“…It was shown unanimously that the best performing PGM-free catalyst was based on iron 85 , 86 that was showed also to be superior compared to platinum. 32 In several investigations, iron showed higher performance compared to cobalt. 85 − 87 Mn, Ni, Zr, and Cu showed inferior performance despite having much higher electroactivity compared to bare AC.…”

Efficient In Situ Utilization of Caustic for Sequential Recovery and Separation of Sn, Fe, and Cu in Microbial Fuel Cells

“…A membrane separator was needed as a barrier to maintain the pH difference between the bioanode and the cathode of each MFC unit, where the bioanode was preferably operated at near neutral pH, and the cathode was sequentially fed with mixed metals effluent from the cathode of the previous MFC unit. An anion exchange membrane (AEM) can selectively transport anions from one side of the membrane to the other, similar to the preferable cation exchange membrane (CEM) for cation ion migration ,. Despite the fact that bipolar membranes can achieve less cross‐over for anions and cations, they have high voltage losses and thus could not be used as effectively for energy‐efficient metal recovery ,.…”