Metal–support interaction regulates structure sensitivity of Ni catalysts in CO 2 methanation

Abstract CO 2 methanation over Ni‐based catalysts is affected by the coupled influences of Ni ensemble structures and metal–support interactions, making the origin of structure sensitivity difficult to clarify. Here, Ni/Al 2 O 3 and Ni/MgAlO x catalysts with comparable Ni particle sizes were constructed to examine how distinct support environments modify size‐dependent methanation. The MgAlO x matrix derived from layered double hydroxides provides a confined coordination environment that stabilizes metallic Ni ensembles with weaker Ni‐O coordination than Al 2 O 3 . On Ni/Al 2 O 3 , decreasing Ni–O coordination with increasing particle size is accompanied by an increase‐and‐plateau trend in surface‐Ni‐normalized activity. Ni/MgAlO x shows a nonmonotonic activity trend with a maximum at approximately 9.2 nm, while 10.4‐Ni/MgAlO x maintains CH 4 selectivity above 99% under high‐conversion conditions. Mechanistic studies indicate that MgAlO x regulates carbon‐intermediate evolution via a dominant CO‐mediated route and slower formate‐associated transformation, balancing CO adsorption and hydrogen availability to limit CO accumulation and favor CH 4 formation.