The influence of Co nucleation in Co[sbnd]Ni single atom alloy on low-temperature methane dry reforming with DFT simulations and microkinetic modeling

Abstract

CO2 reacting with CH4 to produce value-added syngas CO and H2 is an attractive approach to utilize CO2 and achieve carbon neutralization. The present work employed the dispersion corrected density functional theory (DFT) and microkinetic modeling to investigate the influence of Co nucleation in CoNi single atom alloy (SAA) on low-temperature methane dry reforming (DRM). It is found that the Co nucleation in CoNi SAA did not alter the most favorable reaction path. That is, CH4 is dehydrogenated to CH* step by step, then CH* is oxidized by O* from CO2 direct decomposition to obtain CHO*, and finally CHO* is dehydrogenated to produce CO. For the decomposition of CO2, the direct decomposition of CO2 prefers over the assisted decomposition of CO2 by H* via COOH* or HCOO* intermediates decomposition to obtain the final product CO. Microkinetic modeling results reveal that the nucleation of single Co atoms to Co dimer or a surface Co layer favors the conversion of methane and CO2 at 773 K but reduces the coke-resistance ability. Reverse water-gas shift does not change the key species on the surface but interferes the product distribution and surface rate-limiting step.