Reactive-Binder Direct Ink Writing of Structured SnO2 Catalyst Supports with Volumetric Incorporation of Fe

Abstract Tin oxide (SnO2) is a chemically stable, redox-active metal oxide widely employed as a catalyst support in heterogeneous reactions, gas sensing, and energy-related applications. Here, we present a reactive-binder strategy for the additive manufacturing of structured SnO2 catalyst supports via direct ink writing (DIW) using a Pechini-derived polymeric complex that acts simultaneously as a rheological modifier and an oxide precursor. This dual role eliminates the need for inert thickeners or foreign oxide binders while contributing to the final solid loading after calcination. The resulting paste exhibits suitable viscoelastic properties for extrusion-based shaping and enables the fabrication of self-supporting structures that retain their geometric integrity after calcination. The printed bodies exhibit an interconnected pore architecture (54.8% mercury-accessible porosity; median intrusion diameter of approximately 138 nm), suitable for precursor infiltration and catalytic functionalization. Coating experiments with Fe-containing species show that, within the examined filament cross-sections, in situ synthesis promotes comparatively homogeneous incorporation, whereas direct deposition results in surface-localized agglomerates. Discrete Si-rich inclusions, most probably introduced during paste preparation, were also identified, indicating that contamination control during processing is required in addition to the binder chemistry. These results show that reactive-binder DIW provides a route for producing structured SnO2 supports accessible to the volumetric incorporation of Fe-containing species, with potential applicability to other single- and mixed-oxide systems relevant to structured catalytic reactors and energy-transition technologies.