Solid–solid catalysis for sustainable alloy synthesis

Abstract 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 single process. Upon co-reduction of a Fe 2 O 3 –NiO mixture with hydrogen, we report a distinct 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 at least two, highlighting its potential relevance for improving reduction kinetics in hydrogen-based ironmaking and alloy production. Specifically, during hydrogen-driven co-reduction of Fe 2 O 3 and NiO, Ni partitioning takes place across metal–oxide interfaces, driven by interface dynamics, during which restructuring continuously regenerates the catalytic sites that promote H 2 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.