• Polak, Spela
• Hacker, Viktor
• Blaschke, Fabio
• Bele, Marjan
• Bitschnau, Brigitte

Abstract

The transition to a CO2-neutral energy landscape is critically dependent on the development of efficient and sustainable hydrogen production methods[1][2]. Iron-based oxygen carriers have shown promise in chemical looping processes but face challenges such as sintering, which affects their long-term stability and performance[3][4]. This study explores the synthesis and application of novel structured oxygen carriers with a core-shell design, aimed at improving hydrogen production efficiency and stability over multiple cycles.<br/><br/>The structured oxygen carriers were synthesized using an environmentally friendly process, combining iron oxide with yttrium-stabilized zirconia (YSZ) as a support material. The core-shell architecture was designed to prevent agglomeration and sintering, thereby maintaining the structural integrity and reactivity of the oxygen carriers. These materials were tested in a fixed bed reactor system, evaluating their performance over 100 cycles. A detailed examination of the coating thickness shows, that the core-shell oxygen carriers (CS-OC) show a uniform dense coating, which prevents the (CS-OC) from sintering (see Fig.1 b) [5]. Therefore, CS-OC demonstrated superior performance compared to conventional iron oxide pellets. The structured design effectively prevented sintering, maintaining a high surface area and porosity, which are critical for efficient gas exchange and hydrogen production. The novel carriers retained over 80% of their oxygen exchange capacity across 100 cycles, showcasing their potential for long-term use in industrial applications (see Fig. 1a). The comprehensive characterization of the different oxygen carriers allows a deep understanding of the effects caused by the sintering phenomena on a micro- and mesoscopic level. Intensive SEM/EDX characterizations show that the YSZ8 material has excellent coating- and distribution- properties in the bulk material of the pellet in combination with the iron oxide.<br/>This work highlights the advantages of using structured oxygen carriers with a core-shell architecture in chemical looping hydrogen production. The innovative design not only enhances the efficiency and stability of the process but also offers a sustainable approach to producing green hydrogen. Future studies will focus on scaling up the production and further optimizing the material properties to meet industrial demands.<br/>

Topics

• impedance spectroscopy
• surface
• scanning electron microscopy
• Oxygen
• Hydrogen
• iron
• Yttrium
• Energy-dispersive X-ray spectroscopy
• porosity
• sintering