The role of Co–Ga2O3 interfaces in methane dry reforming

Abstract

As the combination of Co with other non-noble metals is a viable way to improve the catalytic properties of Co in methane dry reforming (DRM), we studied an impregnated Co₃O₄/β-Ga₂O₃ powder catalyst to understand the influence of Ga and the catalytic role of the Co–Ga₂O₃ interface and the intermetallic compound CoGa in DRM. Co₃O₄/β-Ga₂O₃ undergoes a series of structural transformations during activation by reduction in hydrogen and under DRM conditions. Contact to the CO₂/CH₄ mixture without hydrogen pre-reduction yields CoGa₂O₄ spinel particles encrusting β-Ga₂O₃ without significant DRM activity. Hydrogen reduction transforms Co₃O₄/β-Ga₂O₃ initially to α-Co/β-Ga₂O₃, before it induces reactive metal–support interaction leading to the formation of bimetallic CoGa particles on β-Ga₂O₃. Subsequent improved DRM activity can be correlated to the decomposition of the intermetallic compound CoGa: according to operando X-ray diffraction CoGa re-transforms into α-Co/β-Ga₂O₃ during DRM. Hydrogen pre-reduction is a prerequisite for high DRM activity on Co₃O₄/β-Ga₂O₃, where intermediarily formed CoGa is decomposed under reaction conditions yielding a pronounced increase in the activity rivalling established noble metal and non-noble metal catalysts. A particular advantage of β-Ga₂O₃ is the suppression of coking and Co deactivation, as observed on a Ga-free Co/SiO₂ catalyst.