The impact bimetallic Ni–Fe deposit configuration has on accessing synergy during plasma-catalytic CO2 methanation

Abstract

Catalytic CO₂ methanation in the presence of plasma is of significant industrial interest due to the lower temperature requirements and capacity for electrification. Advancing catalyst design is crucial for improving the feasibility of plasma-catalytic methanation for industrial applications. The potential for harnessing bimetallic catalyst synergies within the plasma-catalytic system exists although understanding in this area remains limited. Here, two distinct synthesis methods were used, wet co-impregnation (WI) and co-deposition precipitation (DP) to load bimetallic Ni–Fe on a γ-Al₂O₃ support such that the Ni–Fe configuration within the catalyst deposits was regulated to be: (i) segregated Janus-like; (ii) Fe-decorated Ni; and (iii) Fe-encapsulated Ni. The extent of interaction between the Fe and Ni was found to influence the nature of the Ni species within the deposit which, if sufficient, invoked a synergy. More intimate contact between the Ni–Fe or a sufficiently large Fe presence (observed in 10%Ni WI and 10%Fe WI), evidenced by the increase in the fraction of Ni(OH)₂ in the deposits, boosted methane productivity by 78% (relative to 10%Ni WI). In the instance where Fe excessively decorated or encapsulated the Ni deposits (observed in the 10%Ni DP and 10%Fe DP) the benefit of bimetallic intimacy was lost (a 90% reduction in methane productivity relative to 10%Ni3%Fe DP). This study highlights the critical role of metal–metal interactions in controlling catalyst performance. The Ni–Fe synergy was found to be translatable between thermal-catalytic and plasma-catalytic environments, underscoring the potential for adapting the benefits of bimetallic catalysts to plasma catalytic systems. The findings from this study will contribute to the development of catalysts toward practical industrial applications.