Additively Manufactured Geopolymer Monoliths as Robust Supports for High Temperature Catalytic Reactions

Additively manufactured geopolymers are emerging as a versatile class of structured materials combining thermal and mechanical resilience for application in extreme environments. In this work, porous geopolymer monoliths were fabricated by material extrusion (MEX) using tailored metakaolin-based pastes, and printability was quantitatively assessed through a rheological protocol that links precursor attributes to processing behavior. The resulting 3D-printed structures (70% porosity, 30 m²/g) retained mechanical integrity after calcination at 800 °C, in contrast to conventionally cast counterparts that suffered severe strength loss. Upon Ni impregnation, temperature-programmed reduction (TPR-H₂) evidenced strong metal-support interactions and the formation of stable nickel aluminosilicate phases, highlighting the role of the alkali rich geopolymer matrix in interfacial stabilization. As a proof of concept, methane steam reforming (MSR) was used to validate functionality under high temperature conditions (800-900 °C). Ni-geopolymer catalysts exhibited stable performance without deactivation over 2 h. These results position 3D-printed geopolymers as thermally stable, interface-engineered supports for high temperature catalytic technologies beyond the specific MSR case study.