Triggering the phase transition of molybdenum di-selenide (MoSe2) 1T@2H by introducing copper (Cu+): experimental insights and DFT analysis for the hydrogen evolution reaction†

Abstract

The quest to find an effective non-precious metal-based catalyst for the hydrogen evolution process has recently garnered widespread attention. Platinum (Pt) and other platinoids are the preferred catalyst for the hydrogen evolution reaction (HER). However, their widespread application is restricted by the scarcity of rare earth reserves and the consequent elevated costs. In this work, we synthesized a distinctive 1T/2H phase structure via a facile hydrothermal technique. Pristine MoSe₂ and Cu–MoSe₂ were deposited on a carbon cloth (CC) and were directly employed as electrodes in HERs, without the use of binders. The structures and basal planes of the as-prepared pristine MoSe₂@CC as well as 3% and 5%Cu–MoSe₂@CC samples were analysed via XRD, and their morphology was examined using field emission scanning electron microscopy (FESEM), revealing that each carbon fibre's surface was evenly covered with wrinkled nano petals in the shape of nanosheets. Elemental mapping using energy dispersive X-ray spectroscopy (EDX) revealed the coexistence of Cu, Mo, and Se, uniformly dispersed over the sample, and their corresponding energy states and binding energies were analysed using X-ray photoelectron spectroscopy (XPS). Findings indicated a substantial reduction in binding energy when copper was present on MoSe₂, which caused the metallic-semiconductor (1T/2H) phase to dominate. This meticulously developed architecture when coated on a carbon fibre substrate exhibited remarkable HER activity with a low onset potential of −113 mV vs. RHE (reversible hydrogen electrode), a Tafel slope of 87.2 mV per decade and excellent cycle stability of 80 h. In addition, density functional theory (DFT) studies conducted on the novel structure predicted that the introduction of Cu⁺ ions into the MoSe₂ monolayer can make interfacial semiconducting MoSe₂ transform into metallic MoSe₂. This transformation is beneficial for speeding up charge transfer between the interfaces, promoting H atom adsorption and desorption kinetics and thus accelerating sluggish HER kinetics, thereby enhancing its catalytic performance. In brief, the present findings provide experimental and theoretical insights into developing advanced functional catalysts using phase engineering for energy-conversion applications.