CH4 Synthesis From CO2 and NH3 Over Oxide‐Supported Ru Catalysts

Abstract

Carbon dioxide (CO2) methanation using H2 is a promising route for carbon capture and utilization (CCU), but securing green H2 remains a critical challenge for carbon‐neutral implementation. Here, we propose a CO2 + NH3 methanation approach, in which NH3 serves as a hydrogen source in place of H2, and develop oxide‐supported Ru catalysts for this process. Activity evaluation of the prepared catalysts revealed that Ru/ZrO2 exhibited the highest CH4 yield of 55.3% at 425°C among the catalysts tested. Coupled mass spectrometry (MS) and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis revealed that surface isocyanate species (NCO*) act as reaction inhibitors, and that the basic character of the oxide support strongly affects the stability of NCO*. The basic character of the oxide support also governs NH3 decomposition activity, which constitutes an elementary step for H2 supply and plays an important role in promoting CH4 formation. Based on these findings, we propose that oxide supports with moderate basic character, such as ZrO2 and TiO2, are well‐suited for CO2 + NH3 methanation. Further optimization of the Ru–oxide interface should enable the development of more active catalysts, facilitating progress toward carbon‐neutral fuel production processes utilizing NH3 as a direct hydrogen source.