Performance of a thermally regenerative ammonia-based flow battery with 3D porous electrodes: Effect of reactor and electrode design

A Self-Stratified Thermally Regenerative Battery Using Nanoprism Cu Covering Ni Electrodes for Low-Grade Waste Heat Recovery

Developing a low-cost and high-performance thermally regenerative battery (TRB) is significant for recovering low-grade waste heat. A self-stratified TRB induced by the density difference between electrolytes is proposed to remove the commercial anion exchange membrane (AEM) and avoid ammonia crossover. The simulation and experiment results show the uneven distribution of NH₃, verifying the feasibility of self-stratified electrolytes. For better power generation performance, nanoprism Cu covering Ni electrodes with a high specific surface area and a stable framework are adopted to provide more reaction active sites for fast charge transfer during discharge. A maximum power density (12.7 mW cm^-2) and a theoretical heat-to-electricity conversion efficiency of 2.4% (relative to Carnot efficiency of 27.5%) are obtained in the self-stratified TRB employing nanoprism Cu covering Ni electrodes. Moreover, the cost-effectiveness, simple structure, and sustainable discharge operation indicate that it will be a potential choice for energy conversion from low-grade heat.

Membrane-less Direct Formate Fuel Cell Using an Fe-N-Doped Bamboo Internode as the Binder-Free and Monolithic Air-Breathing Cathode

Commercial applications of direct liquid fuel cells require a high-performance, cost-effective, robust, and mechanically/chemically stable cathode for the oxygen reduction reaction. In this study, a membrane-less direct formate fuel cell (DFFC) was constructed by using a Fe-N-doped bamboo internode as the binder-free and monolithic air-breathing cathode and a Pd-electrodeposited graphite rod as the anode. The effect of the preparation procedures including alkali activation, pyrolysis with (NH₄)₃PO₄, and solvothermal treatment with iron phthalocyanine on the physicochemical properties of the cathode is studied with respect to the textural structure, electrical conductivity, and heteroatom incorporation. The results indicated that the resulting cathode exhibited proper distribution of primary/secondary pores for the transport of reactants and ions. Additionally, these procedures effectively increased the electrical conductivity and heteroatom incorporation in the carbon matrix of the as-obtained cathode. The fabricated membrane-less DFFC delivered an open-circuit voltage of 1.04 V and a maximum power density of 10.01 ± 0.16 mW cm^-3 with a limiting current density of 48.95 ± 1.84 mA cm^-3. In addition, this DFFC achieved a high columbic efficiency of 92.3% after 7 h of discharge with one-fueling. Furthermore, the 110 h discharge test at 10 mA cm^-3 demonstrated that the DFFC fabricated with the Fe-N-doped bamboo internode cathode exhibited good stability, showing its promising application as an inexpensive power supply in portable electronics.