In situ topochemical carbonization derivative Co-Ni alloy@Co-Co2C for direct ethanol synthesis from syngas

Highlights: • A new catalyst of Co^δ+-Co₂C decorated-Co-Ni alloys was fabricated from using hydrotalcite. • The chemical state of Co was adjusted via electron-transfer from Co to Ni. • Co^δ+-Co₂C active sites improved the dissociatively adsorbed CO on Ni-Co alloys. • The formation of Ni-Co alloy@Co-Co₂C inhibited Ni volatilization from the catalyst. • The balanced associatively and dissociatively adsorbed CO increased ethanol selectivity. In this work, Co^δ+-Co₂C decorated-Co-Ni alloy nanoparticles (NPs) loaded on Mg-Al-O complex oxides were fabricated via an in-situ reduction and topochemical carbonization strategy by using hydrotalcite as the precursor. The Co^δ+-Co₂C decorated-Co-Ni alloys were obtained via the following process: (I) after reduction, Co-Ni alloy was obtained and Co could donate electrons to Ni in the Co-Ni alloy NPs; (II) in syngas atmosphere, some of cobalt atoms on the surface of Co-Ni NPs reacted with CO and were converted to Co₂C. Resultantly, in the reaction process, Co-Ni alloy NPs were transformed into Ni-Co alloy@Co-Co₂C, a core-shell structure with Ni-Co alloy core and Co-Co₂C shell. When used as the catalysts for direct ethanol synthesis (DES) from syngas, the bimetallic Co-Ni alloy@Co-Co₂C catalyst performed excellent selectivity to ethanol, owing to the regulation of dissociatively and associatively adsorbed CO by Co^δ+-Co₂C active sites formed on the surface of Co-Ni alloy NPs. Moreover, the mutual dilution between Co and Ni in the Co-Ni alloy NPs inhibited the generation of heavy hydrocarbons, further improving the selectivity to alcohols. The total alcohol selectivity of 43.0% and ethanol occupied 45.2 wt% could be reached over the optimal catalyst.