Insight into Mass and Charge Transports in Alkaline Direct Ammonia Fuel Cell with Anti-Ammonia Poisoning Fe-N-C Cathode

Abstract

The ammonia crossover that poisons the conventional cathode catalysts and damages the cell performance and efficiency is one of the paramount bottlenecks limiting the development of direct ammonia fuel cells (DAFCs). Synthetizing the ammonia tolerance catalysts have been proven to be an effective avenue to solve the above-mentioned problems, however, the mass and charge transports within the anti-ammonia poisoning electrodes has not been fully elucidated. Herein, an alkaline DAFC with anti-ammonia poisoning Fe-N-C cathode is reported, and the main effort is expended on investigating the impact of mass and charge transports on cell performance, internal resistance, and operating stability. The alkaline DAFC exhibits a thermodynamic efficiency as high as 88.6%, higher than that of hydrogen-based fuel cells. The preliminary experimental results indicate that the performance of DAFC with anti-ammonia poisoning Fe-N-C cathode is higher than that of conventional Pt/C cathode under the same catalyst loading. The impressive open-circuit voltage of 0.74 V and peak power density of 107 mW cm-2 are obtained under atmospheric pressure and 80 oC, which is primarily ascribed to both the anti-ammonia poisoning of Fe-N-C catalyst and the facilitated mass and charge transports. Furthermore, the voltage curve of DAFC is quite stable during the constant-current discharging at 100 mA cm-2 for 10-hour, demonstrating the good durability of DAFC with anti-ammonia poisoning Fe-N-C cathode.

Keywords: Fuel cell, Direct ammonia fuel cell, Fe-N-C catalyst, Ammonia tolerance, Mass and charge transports