Density functional theory study on Support-Promoted CH4 reforming in Ni-Based oxygen carriers for chemical-looping conversion

Metal oxides play a pivotal role in the conversion of carbonaceous fuels. Nickel-based oxides, due to their affordability and high C-H activation activity, are regarded as promising oxygen carriers (OCs) for CH4 chemical looping technologies. Additives like Al2O3, ZrO2, and MgAl2O4 are used to boost the reactivity of OCs and mitigate agglomeration of OC particles at elevated temperatures. Despite extensive experimental studies on support selection, the influence of support materials on CH4 conversion remains unclearly. This research analyzed and compared the kinetic pathways of CH4 conversion on the supported and unsupported nickel-based OCs, utilizing the Density Functional Theory (DFT) model, to determine the rate limiting step (RLS) in the chemical looping process. The most promising support, NiAl2O4, weakens the Ni -C bond due to pronounced interaction between the OCs and supports, thereby leading to a reduced activation energy barrier for CH4 dehydrogenation. By probing the relationships between reaction kinetic barriers and critical electronic properties of OCs, a screening strategy is proposed to accelerate the development and optimization of novel OC/support materials for CH4 chemical looping conversion.