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 Fe2O3–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 Fe2O3 and NiO, Ni partitioning takes place across metal–oxide interfaces, driven by interface dynamics, during which restructuring continuously regenerates the 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. (Figure presented.)