No abstract

The use of non-platinum group metal (non-PGM) catalysts and liquid fuels is a good way to reduce the burden of commercialization and supply in fuel cells. However, it is very difficult to reach the power performance of commercial hydrogen–air fuel cells, 1.0–1.2 W cm–2, with only non-PGM catalysts. In this study, we synthesize a crustlike Cu@NiCo/C nanocomposite as an anode catalyst for a direct liquid hydrazine fuel cell via facile polyol reduction by injecting a Ni–Co solution into a Cu solution. By systematically investigating their electrocatalytic performance toward hydrazine oxidation in an alkaline solution, an appropriate proportion of three different non-PGM metals is carefully selected. For further investigation, we conduct various electrochemical analyses on Cu@NiCo/C nanoparticles, namely, X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), and Tafel plot analyses, and confirm that the introduction of copper facilitates water adsorption and increases the conductivity of the catalyst. As a result, the application of Cu@NiCo/C as the anode catalyst of the hydrazine fuel cell can achieve a phenomenal power density of 1.08 W cm–2. Importantly, the crusty structure maintains its shape after harsh single-cell testing. This strategy provides not only further insights into alkaline liquid fuel cells using non-PGM catalysts but also the possibility for replacing hydrogen fuel cells.

Finding high-performance, low-cost, efficient catalysts for oxygen reduction reactions (ORR) is essential for sustainable energy conversion systems. Herein, highly efficient and durable iron (Fe) and cobalt (Co)-supported nitrogen (N) and sulfur (S) codoped three-dimensional carbon nanofibers (FeCoÀ N, S@CNFs) were synthesized via electrospinning followed by carbonization. The as-prepared FeCoÀ N,S@CNFs served as efficient ORR catalysts in alkaline 0.1 m KOH solutions that were N 2 and O 2saturated.The experimental results revealed that FeCoÀ N,S@CNFs were highly active ORR catalysts with defectrich active pyridinic N and pyrrolic N and metal bonds to N and S atom sites, which enhanced the ORR activity. FeCoÀ N,S@CNFs exhibited a high onset potential (E onset = 0.89 V) and half-wave potential (E 1/2 = 0.85 V), similar to the electrocatalytic activity of commercial Pt/C. Additionally, the durability of the as-prepared FeCoÀ N,S@CNFs catalysts was maintained for 14 h with longterm stability and high tolerance to methanol stability, accounting for their excellent catalytic ability. Furthermore, CoÀ N@CNFs, FeÀ N@CNFs, and varying Fe and Co ratios were compared with those of FeCoÀ

Fe-N-C materials are currently the most promising non-noble-metal-based ORR electrocatalyst, but their low density of surface active sites compared with Pt/C necessitates improving their utilization via porous structures. Previously, we studied modified Fe-N-C catalyst for the oxygen reduction reaction (ORR) in the cathodes of alkaline hydrazine liquid fuel cells (AHFC). Fe-N-C with magnetite particles and hierarchical pore structure was prepared by steam activation. The steam activation process significantly improves the power performance of the AHFC as indicated by the lower IR and activation voltage losses. The steam activation transformed the Fe3C nanoparticles in Fe-N-C into larger Fe3O4 particles, which caused the electrode surface to become more hydrophilic. Here, elimination of the Fe3O4 nanoparticles by acid leaching was conducted to investigate the effect of Fe3O4 nanoparticles, resulting in enhancing power performance for alkaline hydrazine liquid fuel cells.