Molybdenum diphosphide (MoP2), a topological semimetal, possesses distinctive properties and applications in catalysis, energy storage, and condensed matter physics. However, synthesizing high-purity MoP2 is complex and often results in undesired stoichiometric by-products. Additionally, the intrinsic orthorhombic crystal structure makes it difficult to synthesize MoP2 in a 2D morphology, which is desirable for device and energy applications. Here, the robust synthesis of MoP2 with a well-defined 2D morphology is achieved using the confined gas-solid phosphorization of a MoS2 precursor on substrates. The use of 2D precursors and the surface confinement provided by the substrate maintain the 2D morphology and result in a thickness-dependent stoichiometry of the phosphorization products. The chemical composition and crystal structure of MoP2 nanosheets are comprehensively characterized. At room temperature, MoP2 nanosheets exhibit metallic transport with high conductivity over 5500 S cm-1. Furthermore, MoP2 nanosheets demonstrate excellent electrocatalytic activity and durability for hydrogen evolution in both neutral and acid mediums. Notably, MoP2 nanosheets possess better durability than amorphous Pt film and commercial Pt/C, positioning MoP2 as a promising catalyst for hydrogen evolution in neutral mediums. This work advances the synthetic chemistry of 2D MoP2 and provides 2D semimetals with a novel member for future explorations in diverse fields.
Keywords: gas‐solid transformation; molybdenum diphosphide; neutral hydrogen evolution; on‐chip electrocatalytic microdevices; surface confinement.
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