Ultrasonic decoating as a new recycling path to separate oxygen side layers of solid oxide cells

Abstract

Hydrogen is considered the most promising solution for the energy transition. To meet the future demand for green hydrogen, electrolyzers are a key technology. Among the established electrolyzers, solid oxide electrolyzers have the highest electrical efficiency and are the subject of intensive research. However, the core of solid oxide electrolyzers, the solid oxide cells (SOC), require a significant amount of critical raw materials, making recycling of these materials crucial. Initial recycling approaches rely on expensive manual labor or hydrometallurgical approaches that generate environmentally hazardous residues. This study investigates ultrasonic decoating as an alternative recycling approach. Ultrasonic decoating is simple, can be automated, and does not require additional hazardous materials. For the study, decoating experiments were performed on different SOC with varying sonication times. The quality of SOC decoating was evaluated by optical image analysis using a decoating efficiency. The chemical composition of the removed particles was investigated to draw conclusions about the selectivity. Overall, it was shown that ultrasonic decoating is a suitable recycling approach to separate the oxygen side layers, the perovskites, of SOC. Complete and selective liberation and separation of the oxygen side layers can be achieved by ultrasonic decoating.