On the genesis of molybdenum carbide phases during reduction-carburization reactions

► Control of carburization variables: tailor the reduced/carbide Mo-phases (single/mixture). ► Mo carburization in two stages: (1) Mo6+-Mo4+; (2) Mo4+-Mo0 and, at once, MoC. ► The carburization process is faster than Mo4+ reduction. ► XPS probed: reduced Mo particles show core-shell structure. ► Core: reduced Mo (Mo2C, MoO2 and/or Mo0); Shell: 2-3 nm of MoO3.