Thermal energy density of a potential solid fuel: experimental investigation

• Ammonium formate was synthesized low-temperature thermal conditions (65°C), achieving ∼8.75 kJ/g gravimetric and ∼11.2 kJ/cm 3 volumetric energy densities. • This solid-state synthesis offers a safer, cost-effective route for producing a stable hydrogen carrier suitable for decentralized energy systems. • FTIR and SEM analyses confirmed the chemical stability and porous crystalline morphology of ammonium formate. This study presents a high-yield synthesis method for ammonium formate (NH 4 HCO 2 ), which is offered as a potential solid fuel, via the stoichiometric reaction of ammonium carbonate and formic acid under mild thermal conditions (65°C). The process improves conversion efficiency and enables crystallization without thermal degradation. Structural characterization using the Fourier Transform Infrared (FTIR) spectroscopy and Scanning Electron Microscopy (SEM) confirmed the present chemical bonds and porous morphology of the final product. Thermodynamic analyses reveal a gravimetric energy density of ∼8.75 kJ/g and a volumetric energy density of ∼11.2 kJ/cm 3 . Ammonium formate offers safer handling, ambient stability, and cost-effective synthesis, making it suitable for clean energy applications, particularly in membrane-free fuel cell systems.