Methanol decomposition on Cu-modified BN, AlN, and TiN monolayers: a comparative study with Cu(111)

Abstract

This study investigates methanol decomposition on Cu-modified two-dimensional AlN, BN, and TiN monolayers as potential catalysts using density functional theory (DFT). Two competing reaction pathways were evaluated: (i) methoxy formation via O–H activation and (ii) hydroxymethyl formation via C–H activation; and were compared with those on Cu(111) as a reference. The results show that Cu(111) remains the lower-barrier reference surface for methanol decomposition. Among the investigated Cu-modified monolayer supports, BN provides the most favorable behavior, with methoxy route apparent barriers closest to those of Cu(111) and lower than those obtained for the corresponding TiN and AlN systems. Electronic-structure analysis indicates that the substitution site controls the local Cu environment, with Cu/B doping producing stronger Cu–N coupling near the Fermi level, whereas Cu/N doping shows deeper Cu d-states and weaker near-Fermi Cu–B coupling. Free-energy analysis at 500 K and 1 atm further supports the relevance of the BN–Cu/B model for the methoxy pathway. TiN-supported systems strongly stabilize several reaction intermediates, producing deep energy minima and inhibiting optimum catalytic performance. AlN systems are mechanistically non-viable, with unstable adsorption and high barriers preventing a continuous low-energy reaction pathway. Overall, BN emerges as the most promising Cu-modified monolayer support although Cu(111) remains the lower-barrier surface.