Selective oxidation of methane to CO on Ni@BOx via reaction-induced vapor migration of boron-containing species onto Ni

Dynamic migration of support-derived species and subsequent encapsulation of supported metal nanoparticles (NPs) are the well-known features of the Strong Metal-Support Interaction (SMSI) effect. Here, we report occurrence of the classical SMSI state in physical mixture of Ni NPs and porous hexagonal boron nitride powder (Ni|pBN) during methane oxidation reaction at 600 celcius, in which Ni NPs are encapsulated by BOx overlayers derived from the pBN component. The SMSI state can switch the methane oxidation selectivity from CO2 on the fresh Ni|pBN catalyst to CO on the used catalyst. The encapsulation of Ni NPs by BOx overlayers has also been observed in Ni/Al2O3 catalyst which is physically mixed with pBN. Comprehensive characterizations confirm that the SMSI state is induced by vapor migration of boron-containing species e.g. BOxHy from pBN to metal surfaces, in which both high reaction temperature and water product play an important role.