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

Abstract

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, andthe 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.