Copper Foam Electrodes for Increased Power Generation in Thermally Regenerative Ammonia-Based Batteries for Low-Grade Waste Heat Recovery

The use of porous copper foam to increase the electrode surface area and power generation in thermally regenerative ammonia-based batteries (TRABs) is proposed and investigated. The incorporation of copper foam leads to a 38% increase in maximum power compared to that of typical copper plate. The electrode thickness not only influences the electrode surface area but also affects mass transfer, especially the ammonia transfer inside the anode. The optimal thickness of copper foam in terms of total charge, power, and power density is 10 mm. The power generation increases as the ammonia concentration is increased to 1 mol/L due to enhanced mass transfer, while further increase in the ammonia concentration (2 mol/L) leads to ammonia crossover and a decrease in power. Electricity generation is stable over 14 discharging batch cycles (>28 h), and the maximum power is maintained in the range of 58 ± 5 mW.