Solid–Solid Catalysis in Sustainable Alloy Synthesis

Metal production causes 10% of global greenhouse gas emissions, with most metals extracted from oxide ores via fossil-based pyrometallurgy including melting. Solid-state hydrogen-driven redox reduction is not only a sustainable alternative, but can also be used to integrate reduction, in-situ alloying of mixed oxides, and microstructure design in one step. Upon co-reduction of a Fe2O3–NiO mixture with hydrogen, we find a new type of solid–solid catalytic interaction between pre-reduced metal (Ni) and a transient oxide (FeO). This interaction accelerates hydrogen-based reduction by a factor of two—a remarkable effect given the scale of global metal production at nearly 2 billion tons annually. Specifically, during hydrogen-driven co-reduction of Fe2O3 and NiO, metal partitioning takes place across the metal-oxide interfaces, driven by interface dynamics during which restructuring continuously regenerates catalytic sites that promote H2 spillover. These findings show that hydrogen-based alloy production is not only more sustainable than fossil-based practices but can leverage kinetic and commercial advantages through solid-solid catalytic effects.