Mechanistic insights into SO2-induced deactivation of Ni-based materials for integrated CO2 capture and methanation

Dual functional materials (DFMs) for cyclic CO₂ capture and methanation exhibit significant potential in mitigating global climate change and achieving carbon neutrality. However, material deactivation caused by SO₂ poisoning presents a major challenge for its industrial applications. Herein, we tailored a kind of Ni-based DFM, and the sulfur poisoning effects on CO₂ adsorption and in-situ conversion were systematically investigated. The experimental results reveal a striking inverse relationship between SO₂ concentration, CO₂ capture capacity, and methane yield. Increasing SO₂ concentration promotes the form of stable sulfate species and undecomposable, lower CO₂ capture capacity which further decreases methane yield with the rate of decrease in methane yield rising sharply from 7.14 % to 85.71 % as the SO₂ concentration increases from 100 ppmv to 1000 ppmv, compared to the methane yield in the absence of SO₂. Physicochemical characterizations demonstrate that SO₂ accumulates on the surface of DFM, initially forming sulfite and oxidizing to sulfate during the CO₂ adsorption process. Furthermore, sulfur poisoning accelerates the oxidation of metallic Ni to Ni²⁺ after cyclic reactions, which suppresses high-temperature basic sites and surface oxygen vacancies of DFM. In-situ DRIFT studies reveal that the deposited sulfate remains stable during H₂ reduction at 340°C, contributing to the decomposition of formate intermediates and ultimately leading to a decrease in methane production.