Oxidative nucleation and growth of Janus-type MnOx–Ag and MnOx–AgI nanoparticles

Abstract

Janus nanoparticles (NPs) containing two chemically distinct materials in one system are of great significance for catalysis in terms of harnessing catalytic synergies that do not exist in either component. We herein present a novel synthetic method of two Janus-type MnO_x–Ag and MnO_x–AgI NPs. The synthesis of Janus-type MnO_x–AgI NPs is based on the oxidative nucleation and growth of Ag domains on MnO first and the subsequent iodization of Ag. A mild and non-disruptive iodization strategy is developed to yield Janus MnO_x–AgI NPs, in which converting Ag to AgI domains with iodomethane (CH₃I) is achieved through partial iodization. Simultaneously, Mn²⁺ species in the primary MnO octahedra are oxidized during the growth of Ag NPs, leading to the formation of amorphous p-type MnO_x domains. Therefore, the as-resultant Janus-type MnO_x–AgI NPs combining two semiconductors into an integrated nanostructure can be used as an efficient photocatalyst for visible-light-driven water oxidation. Janus MnO_x–AgI NPs show an expected photocatalytic activity even in the absence of Ru(bpy)₃Cl₂ as an electron mediator. This intriguing synthesis may offer a new opportunity to develop asymmetric nanostructures of two semiconductors that will potentially be efficient photocatalysts for solar-driven water splitting.