Synthesis of Anti-poisoning Spinel Mn–Co–C as Cathode Catalysts for Low-Temperature Anion Exchange Membrane Direct Ammonia Fuel Cells

Abstract

Low-temperature anion exchange membrane direct ammonia fuel cells (AEM-DAFCs) have emerged as a potential power source for transportation applications with the recognition that liquid ammonia is a carbon-free hydrogen carrier and facilitates storage, refill, and distribution. However, ammonia crossover from the cell anode to cathode can decrease the fuel efficiency, drop the voltage, and poison the cathode catalysts. In this work, the Mn−Co spinel on three different carbon supports [BP2000, Vulcan XC-72R, and multiwalled carbon nanotubes (MWCNTs)] has been successfully synthesized and demonstrated a high oxygen reduction reaction (ORR) activity with good ammonia tolerance. The structure and composition of the obtained Mn−Co−C catalysts were characterized by high-angle annular dark-field scanning transmission electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. All three catalysts exhibit superb ammonia tolerance, and Mn−Co−BP2000 demonstrates the highest ORR activity, even better than the commercial Pt−C in the presence of ammonia. When paired with the commercial PtIr−C anode, the Mn−Co−BP2000 cathode improved the peak power density of single cells from 100.1 mW cm −2 for the Pt−C cathode to 128.2 mW cm −2 under a 2 bar backpressure in both electrodes at 80 °C. All the results have manifested that Mn−Co−BP2000 is a good cathode catalyst for low-temperature AEM-DAFCs.

Constructing atomically-dispersed Mn on ZIF-derived nitrogen-doped carbon for boosting oxygen reduction

“…Manganese (Mn) adjacent to Fe on the periodic table has the outer layer electrons of 3d 5 4s 2 . The adsorption energy of Mn-N-C for *OH is lower than that of Fe-N-C, which is consistent with the density functional theory (DFT) analyses ( Xiong et al, 2019 ; Hu et al, 2021 ; Li et al, 2021 ; Peng et al, 2021 ; Zhou et al, 2022 ). Besides, Mn is among the richest metals on earth.…”

Optimization of the Cathode Catalyst Layer for Boosting Direct Ammonia Fuel Cell Performance by Orthogonal Tests

“…For the CGDE, the Mn−Co spinel catalyst on BP2000 (MCS-BP) was synthesized according to our previous work 26 and was used as the cathode catalyst in this work. To reduce the experimental error caused by the carbon paper (28BC, SGL Carbon, Wiesbaden, Germany), the carbon paper has been heat-treated (340 °C for 30 min in the air) before use.…”

Efficient anode PtIr catalysts for anion exchange membrane direct ammonia fuel cells

“…Next, we selected the catalyst Mn-Co spinel studied in the group as the ORR catalyst. Due to its better ORR performance, a battery with higher power density was obtained [14]. In order to improve the activity of oxygen reduction on the cathode side, we applied a pressure of 0.1 MPa to both ends of the cell, so that the limitation of oxygen reduction was reduced.…”