CO₂ methanation has recently emerged as a process that targets the reduction in anthropogenic CO₂ emissions, via the conversion of CO₂ captured from point and mobile sources, as well as H₂ produced from renewables into CH₄. Ni, among the early transition metals, as well as Ru and Rh, among the noble metals, have been known to be among the most active methanation catalysts, with Ni being favoured due to its low cost and high natural abundance. However, insufficient low-temperature activity, low dispersion and reducibility, as well as nanoparticle sintering are some of the main drawbacks when using Ni-based catalysts. Such problems can be partly overcome via the introduction of a second transition metal (e.g., Fe, Co) or a noble metal (e.g., Ru, Rh, Pt, Pd and Re) in Ni-based catalysts. Through Ni-M alloy formation, or the intricate synergy between two adjacent metallic phases, new high-performing and low-cost methanation catalysts can be obtained. This review summarizes and critically discusses recent progress made in the field of bimetallic Ni-M (M = Fe, Co, Cu, Ru, Rh, Pt, Pd, Re)-based catalyst development for the CO₂ methanation reaction.

CO₂ methanation has great potential for the better utilization of existing carbon resources via the transformation of spent carbon (CO₂) to synthetic natural gas (CH₄). Alkali and alkaline earth metals can serve both as promoters for methanation catalysts and as adsorbent phases upon the combined capture and methanation of CO₂. Their promotion effect during methanation of carbon dioxide mainly relies on their ability to generate new basic sites on the surface of metal oxide supports that favour CO₂ chemisorption and activation. However, suppression of methanation activity can also occur under certain conditions. Regarding the combined CO₂ capture and methanation process, the development of novel dual-function materials (DFMs) that incorporate both adsorption and methanation functions has opened a new pathway towards the utilization of carbon dioxide emitted from point sources. The sorption and catalytically active phases on these types of materials are crucial parameters influencing their performance and stability and thus, great efforts have been undertaken for their optimization. In this review, we present some of the most recent works on the development of alkali and alkaline earth metal promoted CO₂ methanation catalysts, as well as DFMs for the combined capture and methanation of CO₂.