Recycling and reuse of ceramic materials from components of waste solid oxide cells (SOCs)

As one of the main waste streams of the manufacturing process of solid oxide cells (SOCs), scrap half-cells - discarded before the deposition of the barrier layer and the air electrode - imply the loss of significant quantities of ceramic composite material containing critical and hazardous elements, namely yttria-stabilized zirconia (YSZ) and NiO. These materials represent more than 90 wt% of an entire anode-supported cell. In this contribution, scrap half-cells were fragmented and subjected to three subsequent milling and sieving (below 25 μm) steps to recover composite NiO-YSZ powders with the appropriate specifications for reuse in SOC manufacturing. The overall characterization in terms of specific surface area, particle size distribution and crystalline phase retention confirmed the suitability of the recovered powders. Half-cells were manufactured including 30 wt% of recovered NiO-YSZ composite powders in their fuel electrode support, produced via tape-casting in combination with 70 wt% of virgin materials. The obtained cells were morphologically, mechanically and electrochemically tested and compared against standard cells constituted by 100 wt% of virgin materials. The electrochemical characterization highlighted 0.68 A cm−2 for the standard and recycled cells, at 600 °C and 0.7 V, while at 650 °C and same voltage both cells measured 1.12 A cm−2. This demonstrates the feasibility of recovering scrap SOCs through the presented method.