Unravelling the role of oxophilic metal in promoting the deoxygenation of catechol on Ni-based alloy catalysts†
Nickel-based alloys have been recognized as promising catalysts for upgrading of bio-oils because of their superior deoxygenation activity. Herein, we present a density-functional theory study on hydrodeoxygenation (HDO) of catechol on three Ni-based (111) surfaces, namely Ni(111), bimetallic Fe@Ni(111) single-atom alloy and NiFe(111) homogeneous alloy. The results show that the partial hydrogenation (PH) and/or transhydrogenation (TH) followed by dehydroxylation (DO) are the dominant reaction pathways of catechol HDO towards phenol formation on the three Ni-based (111) surfaces. Specially, TH via *H-and-metal-assisted intramolecular H-transfer is identified as an effective hydrogenation route with a lowered activation barrier compared to the conventional hydrogenation mechanism catalyzed by metals. It is revealed that the deoxygenation performance in catechol HDO can be greatly enhanced by increasing the content of alloyed oxophilic Fe, which, however, could cause the side effect of difficult removal of over-bound *OH on an over-oxophilic surface. The composition of a secondary oxophilic metal in an alloyed surface should be an optimizable parameter as important as altering oxophilic metals alloyed into an active metal phase.