Engineering 3D-printed molybdenum carbide catalysts for selective CO₂ reduction to CO

Abstract

Additive manufacturing has significantly advanced catalyst design by enabling the creation of complex, customizable, and reproducible structures. This study explores how various strategies in the preparation of 3D-printed MoₓC/Al₂O₃ catalysts can enhance CO production efficiency in the Reverse Water Gas Shift (RWGS) reaction. The parameters investigated include the impregnation method, incorporation of co-catalysts (Ni, Fe, Co, and Cu), and architectural modifications to the 3D-printed structures. A key finding revealed that in-situ carburization consistently outperforms ex-situ carburization, achieving a 15 % increase in CO yield at 873 K. Among the co-catalysts tested, the incorporation of Ni onto the MoₓC/Al₂O₃ structures demonstrated superior catalytic activity, particularly at elevated temperatures (873 K). This improved performance was further validated through Density Functional Theory (DFT) simulations, revealing that small clusters of Ni on MoC can activate CO₂and H₂ with negligible free energy barriers. Structural optimization of the 3D architecture, such as variations in printing pattern and fiber diameter, also enhanced catalytic performance, due to improved external mass diffusion of reactants. The optimal design, featuring a (1–3–5) printing pattern with a 600 μm fiber diameter, achieved this enhancement while maintaining an acceptable pressure drop within the reactor. Overall, this study underscores the transformative potential of 3D printing in catalyst production, offering flexibility to optimize catalyst geometry and enhance performance in thermochemical processes relevant to the chemical industry.