Rational control of particle size and basic sites of NiFe/TiO2 catalysts to improve CO2 low-temperatures methanation performance and anti-coking ability

The critical challenge in overcoming the efficiency bottleneck of CO 2 methanation is the simultaneous optimization of low-temperature activity and coking resistance in Ni-based catalysts. This study employed Fe to modify Ni/TiO 2 , and the synthesized NiFe/TiO 2 catalyst was thoroughly characterized to elucidate its structural properties, followed by comprehensive assessment of its catalytic performance. Systematic characterization revealed that Fe incorporation enhances metal dispersion and modulates the electronic environment of Ni, promoting the formation of NiFe alloys. Additionally, the oxygen vacancies generated by Fe species improve the local environment of NiO, promote the effective reduction of Ni 2+ , and weaken the interaction between NiFe and the support, enabling NiFe catalysts to achieve reduction at lower temperatures. By optimizing the Ni/Fe ratio, the distribution of basic sites on the catalyst surface was precisely tuned, which was crucial for CO 2 activation, adsorption of oxygenated intermediates and carbonaceous intermediate. The Ni 3 Fe 1 /TiO 2 catalyst (Ni/Fe = 3) characterized by small metal particles, high NiFe alloy, and abundant medium-strength basic sites, exhibits exceptional performance at 280 °C. It achieved 86.6% CO 2 conversion with 98.1% CH 4 selectivity, representing 19.4% and 3.8% improvements respectively over the Ni/TiO 2 catalyst. DFT calculations further confirmed that NiFe alloy strengthens the adsorption of oxygenated intermediates (O*, OH*, H 2 O*), promoting CO 2 activation, while weakening carbonaceous species (C*) adsorption.