A thermally regenerative ammonia-based battery (TRAB) is a new electrochemical energy device used for the recovery of low-grade waste heat. The use of a three-dimensional (3D)-printed Cu/C composite electrode was proposed to promote electrode stability and to solve the high mass transfer resistance inside the porous electrode. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) tests indicated the successful copper electroplating on the surface of 3D-based porous carbon. The performance of TRAB using Cu/C electrodes (TRAB-Cu/C) was compared with that of TRAB with copper foam electrodes (TRAB-Cu), and the effects of electrode pore size were investigated. Results showed that the maximum power density of TRAB-Cu/C was 42.3 +/- 2.4 W m(-2), which was 5.8% higher than that of TRAB-Cu (40 +/- 1.6 W m(-2)). The pore size of the Cu/C composite electrode significantly influenced the electrode specific surface area and mass transfer inside the porous electrode. The highest maximum power density (42.3 W m(-2) was obtained in a TRAB-Cu/C with a pore size of 0.6 mm.