Uniting 3D printing and photo-thermal catalysis to achieve CO2 hydrogenation over cordierite monolithic catalysts

Abstract

CO₂ hydrogenation is a highly important reaction, as it reduces the CO₂ concentration in the air and provides important chemicals. Among the CO₂ conversion routes, photo-thermal catalytic CO₂ hydrogenation represents a promising technology. However, the design and fabrication of efficient catalysts are significantly crucial, especially catalysts with high mass transfer and heating efficiencies. Combining the advantages of 3D printing and photo-thermal catalysis, a customized cordierite monolithic catalyst was successfully prepared in this study, which can achieve a high CO₂ hydrogenation activity at a low temperature. The internal relations among macrostructure, light absorption/heat transfer, and catalytic performance were revealed in detail. The results showed that the reduction treatment of the monolithic catalyst could improve the catalytic performance obviously. This phenomenon was mainly attributed to the changes in the valence states of Co and Cu, and an increase in the number of oxygen vacancies in the catalytic coating. By suitably decreasing the transverse and longitudinal pore sizes, the catalytic performance of the monolithic catalyst was effectively improved. The main products are CO and CH₄, and their highest activities reached 67.42 and 25.5 mmol g⁻¹ h⁻¹, respectively, at 200 °C with a H₂/CO₂ volume ratio of 4/1. The high catalytic performance was derived from the improvement of light absorption, heat transfer and reactive area, which collectively promoted the electron–hole pairs generated on the catalyst surface and accelerated the adsorption and diffusion of reactants on the catalyst surface.