Geometric configuration-dependent ortho-to-para hydrogen conversion over pure α-Fe2O3 catalysts

Abstract

The catalytic conversion of ortho-to-para hydrogen (o–p H₂) is crucial for addressing the challenges of hydrogen liquefaction and storage. Iron-based catalysts have been shown to be the most promising candidates for o–p H₂ conversion due to their low cost and stable catalytic performance. Nevertheless, the exact geometric configuration of iron oxide influencing the catalytic efficiency remains unclear. In this work, three types of α-Fe₂O₃ nanocrystals with controlled geometric configurations including rhombohedral, hexagonal and pseudo-cubic were synthesized via a hydrothermal method. The microstructure and magnetic properties of these nanoparticles were systematically investigated to elucidate their catalytic behavior. The catalytic activity of the α-Fe₂O₃ decreased in the order: rhombohedral > hexagonal > pseudo-cubic. The geometric configuration-dependent behavior was found to correlate strongly with the magnetic properties. The low remanent magnetization and coercivity were in favor of enhancing o–p H₂ conversion. Our study provides new insights into the design and synthesis of iron oxide catalysts for exploring the key factors in optimizing o–p H₂ conversion efficiency.