Intermetallic compounds of Ni and Ga as catalysts for the synthesis of methanol

In this work, we present a detailed study of the formation of supported intermetallic Ni-Ga catalysts for CO2 hydrogenation to methanol. The bimetallic phase is formed during a temperature-programmed reduction of the metal nitrates. By utilizing a combination of characterization techniques, in particular in situ and ex situ X-ray diffraction, in situ X-ray absorption spectroscopy, transmission electron microscopy combined with electron energy loss spectroscopy and X-ray fluorescence, we have studied the formation of intermetallic Ni-Ga catalysts of two compositions: NiGa and Ni5Ga3. These methods demonstrate that the catalysts with the desired intermetallic phase and composition are formed upon reduction in hydrogen and enable us to propose a mechanism of the Ni-Ga nanoparticles formation. By studying the effect of calcination prior to catalyst reduction, we show that the reactivity depends on particle size, which suggests that the reaction is structure sensitive.