Influence of polyvinyl alcohol space holders on the microstructure and porosity of sintered powder metallurgy electrodes

Porous metallic electrodes are essential for energy storage and conversion technologies due to their high surface area, enhanced ionic transport, and increased number of electroactive sites. The objective of this study is to investigate the influence of polyvinyl alcohol (PVA) space holders on the microstructure, porosity, and structural connectivity of sintered powder metallurgy iron electrodes, establishing correlations between processing parameters and electrochemical performance. In this study, porous iron electrodes were fabricated via powder metallurgy using polyvinyl alcohol (PVA) as a space holder, aiming to optimize electrochemical performance. The powder mixtures were uniaxially compacted at 60, 80, 100, and 120 MPa, followed by a two step sintering process, with an intermediate step at 300 °C for controlled PVA removal and final sintering at 1,050 °C for 30 min under argon with preliminary vacuum. The influence of PVA content on porosity, pore morphology, and microstructural connectivity was systematically evaluated. Morphological analyses showed that PVA promoted the formation of open and interconnected pores, achieving porosity levels that enhance ionic transport and increase the number of electroactive sites compared to conventional powder metallurgy electrodes. Variation in compaction pressure allowed tuning of pore size distribution and densification, enabling a balance between mechanical stability and high porosity. Structural analyses confirmed the stability of the metallic phase and minimal oxidation. These results demonstrate that the PVA space-holder technique enables controlled microstructure design to directly improve electrochemical performance, providing a clear design advantage over conventional electrodes for batteries, fuel cells, and other energy devices.