Mastering the Foreign Ionic Radius in CeO₂ Supports of Ni-Based Catalysts for Efficient CO₂ Methanation

A Ni-based catalyst is a common non-noble-metal system for CO2 methanation, and metal modification for the support is an effective method to further improve its activity. Doping metals with various ionic radii already exhibited different effects on the methanation performance, but the promotion mechanism remains indistinct. Herein, we report a universal doping strategy to fabricate Ni-based catalysts by tailoring foreign ions (Al3+, Zr4+, Y3+, and Sm4+) with different radii in CeO2. Among them, Ni/Ce0.9Al0.1Ox exhibited the highest catalytic performance (72.4% of CO2 conversion at 300 °C) compared with other catalysts at all temperatures and with the lowest kinetic temperature range. Furthermore, the change in the foreign ionic radius had a variety of effects on the structure of the catalysts, in which the specific surface area and oxygen vacancy concentration were the main factors. According to mechanical measurements, the doping of foreign ions reduced the temperature of the started methanation and inhibited CO formation, resulting in enhanced catalytic activity CO2 conversion and increased CH4 selectivity. The hydroxyl groups derived from the oxygen vacancy facilitated the transformation of CO2 to CH4 via the HCOO* path. This work contributes to developing a promising approach to controlling the performance of CO2 methanation by regulating the foreign ionic radius.