Formation of Ni-rich Ni-Ga alloy clusters on the (221) surface of Ni5Ga3 intermetallic compounds during CO2 hydrogenation: An in-situ TEM study

Ni-Ga alloys are the most promising bimetallic alloy catalysts for CO 2 hydrogenation due to their high activity and selectivity. This study used in-situ transmission electron microscopy (TEM) to clarify the structural changes in the Ni 5 Ga 3 intermetallic compound catalysts during the CO 2 oxidation and CO 2 hydrogenation processes. The results showed that as the temperature increased from 50ºC to 300ºC under CO 2 conditions, crystalline Ga oxides, primarily the β -Ga 2 O 3 phase, formed on the Ni 5 Ga 3 (211) surface, resulting in the formation of parallel moiré fringes. At the same time, Ni-rich Ni-Ga alloy nanoclusters appeared due to the excess Ni on the surface. Under H 2 /CO 2 conditions, Ni-rich Ni-Ga alloy nanoclusters were also observed, but the formation of Ga oxide was limited. Electron energy loss spectroscopy (EELS) analysis also revealed the presence of Ga oxide but not Ni oxide phase.