Optimizing Mo2C-based Catalytic System for Efficient CO2 Conversion and CO Selectivity through Carbon-nitrogen Supporting and Potassium Promotion

Abstract

Preparing highly active, stable, and selective catalysts for the reverse water gas shift (RWGS) reaction is challenging because of the aggregation of the active catalyst at high RWGS reaction temperatures and deactivation of the active sites. Herein, we present a comparative evaluation and optimization of a molybdenum carbide system using a carbon-nitrogen (CN) support and alkali promotion. Hydrothermally prepared MoO3 nanorods were carburized at 700oC using H2:CO (4:1) to prepare unsupported Mo2C, while CN-supported Mo2C (Mo2C@CN) was prepared using Mo-based metal-organic framework (Mo-MOF) as a sacrificial template. The as-prepared Mo2C@CN catalytic system was found to be highly active in the RWGS reaction in comparison with the unsupported Mo2C, where CO2 conversion percentage was around 76% at 700oC, combined with high CO selectivity (87%) and very reduced CH4 selectivity (2%). The addition of potassium as a promoter enhanced CO selectivity (99%). The active catalyst performance was stable during the catalysis process and for up to 100h, which imposes the effect of the CN support in preventing the aggregation of Mo2C and keeping its active sites in direct contact with the reactant. This work presents an effective strategy for improving the active catalyst dispersion and reducibility in synergy with the promoter effect to optimize the RWGS reaction output.