Tailoring of Surface Acidic Sites in Co-MoS₂ Catalysts for Hydrodeoxygenation Reaction

CoMo sulfides are typical catalysts for selective hydrodeoxygenation (HDO) of phenolics to aromatics which is important in bio-oil upgrading. However, it is still a challenge to promote the intrinsic activity of Co-MoS₂ catalysts. Defect chemistry provides a good option to improve surface reactivity in catalysis. In this work, we report a facile H₂O₂ etching method to tailor the concentration of surface acidic sites. The molar ratio of H₂O₂/MoS₂ can be altered to tune sulfur defects on the MoS₂ surface for stabilizing Co species to form CoMoS active sites. The optimized Co-MoS₂-2 catalyst, with the highest concentration of acidic sites, exhibits 3.4 times higher activity than the Co-MoS₂-0 sample in the HDO of p-cresol to toluene. It is also found the HDO activity shows a linear relationship with the amount of surface acid (both Lewis and Brønsted acid) over the Co-MoS₂-x catalysts. We believe that the understanding of the role of surface acidity would provide new opportunities for the rational design of efficient Co-MoS₂ catalysts.