Exploring the 3D printing of molybdenum carbide-based catalysts for the reverse water gas shift reaction: A multi scale study

A new methodology for preparing 3D printing molybdenum carbide-based catalysts with direct ink writing is presented. CO₂ conversion experiments through the reverse water gas shift reaction showed that the catalytic behavior of 3D-Mo_xC/Al₂O₃ catalysts is controlled by the crystallite size and crystalline phase, which in turn were dependent on the Mo loading. The formation of cubic δ-MoC and hexagonal η-Mo₃C₂ was prevalent in small crystallite sizes at low loading of Mo, and α/β-Mo₂C in larger crystallite sizes at high loading of Mo. Operando DRIFTS experiments points out that hydroxyl species present on the surface of Al₂O₃ play a major role in bicarbonate formation that leads to the formation of formates, which eventually decomposes to CO and H₂O. The produced structures were mechanically stable and kept their structural and textural properties after reaction. Therefore, this work introduces new perspectives for scaling-up 3D printed structures based on molybdenum carbide.