Metal support interaction governs the dry reforming activity in a modified sol-gel prepared CeO2 supported high entropy CoCuFeMnNi catalyst

Abstract

This study demonstrates two key concepts in the area of heterogeneous catalytic chemistry. One is the preparation of a high entropy alloy supported system/catalyst where unlike the conventional sol-gel process one of the components (metal) is already in a final form of metallic nanoparticle and the other component (oxide) needs to be prepared from its precursor. Second key concept is the demonstration of metal support interaction (MSI) in high entropy alloys (HEA) catalysis. CoCuFeMnNi, which is a FCC structured HEA alloy becomes an active dry reforming catalyst only when it is supported over CeO2 oxide, a clear demonstration of metal support interaction. Importantly, the CoCuFeMnNi supported CeO2 catalyst (CoCuFeMnNi/CeO2) displays noteworthy features of substitutional effects where XPS is unable to identify the surface concentration of majority of the HEA entities. This is further corroborated by TEM where substantial demonstrations of HEA substitution in CeO2 is visibly clear. It is envisaged that this substitutional effect is the one which causes the lattice oxygen activation, an important active species during dry reforming reaction. Transient studies are carried out to understand the surface chemistry of the interaction of methane and CO2 and this study establishes that CoCuFeMnNi/CeO2 follows the conventional DRM mechanism where methane decomposes first to give hydrogen and carbon and CO2 reacts with the deposited carbon to give CO. Overall, CoCuFeMnNi/CeO2 represents good activity and reasonable stability, much higher than that of CeO2 or CoCuFeMnNi alone. This study can be taken as a proof of concept to demonstrate that MSI can be generated in the HEA catalysts and the preparation methodology adopted in this study is a handy tool to achieve this.