Manganese Doping of MoSe₂ Promotes Active Defect Sites for Hydrogen Evolution

Abstract

Transition-metal dichalcogenides (TMDs) are being widely pursued as inexpensive, earth-abundant substitutes for precious-metal catalysts in technologically important reactions such as electrochemical hydrogen evolution reaction (HER). However, the relatively high onset potentials of TMDs relative to Pt remain a persistent challenge in widespread adoption of these materials. Here, we demonstrate a one-pot synthesis approach for substitutional Mn-doping of MoSe 2 nanoflowers to achieve appreciable reduction in the overpotential for HER along with a substantial improvement in the charge-transfer kinetics. Electron microscopy and elemental characterization of our samples show that the MoSe 2 nanoflowers retain their structural integrity without any evidence for dopant clustering, thus confirming true substitutional doping of the catalyst. Complementary density functional theory calculations reveal that the substitutional Mn-dopants act as promoters, rather than enhanced active sites, for the formation of Se-vacancies in MoSe 2 that are known to be catalytically active for HER. Our work advances possible strategies for activating MoSe 2 and similar TMDs by the use of substitutional dopants, not for their inherent activity, but as promoters of active chalcogen vacancies.

Co‐Doped MoSe2 Nanoflowers as Efficient Catalysts for Electrochemical Hydrogen Evolution Reaction (HER) in Acidic and Alkaline Media

“…The crystallographic structure of most TMDCs is similar, and conveniently, the material properties can be significantly modified depending on the size, polarizability and charge of both constituting elements. In MoSe 2 , each layer of Mo is sandwiched between two layers of hexagonally close‐packed Se atoms, and the atomic layers are stacked by weak van‐der‐Waals interactions . It is already well established that active sites, intrinsic activity and conductivity govern the electrocatalytic HER activity .…”

“…Therefore, many strategies were employed to improve the performance of MoSe 2 . In addition to directly creating edge‐rich morphology, forming additional active catalytic sites by doping of the TMDC with other transition metals has gained much attention . High affinity of Co to the saturation of the edges of layered d ‐metal dichalcogenides is well established and is extensively applied in catalysis .…”

Unveiling the Origin of the High Catalytic Activity of Ultrathin 1T/2H MoSe2 Nanosheets for the Hydrogen Evolution Reaction: A Combined Experimental and Theoretical Study

“…In recent years, there has been an ever-growing interest in the development of efficient, earth-abundant and inexpensive Pt-free electrocatalysts with long-term stability.O ft hese, molybdenum (Mo)-based compounds including Mo 2 C, [17][18][19] MoS 2 [20,21] and MoSe 2 [22,23] nanostructured materials have demonstrated remarkable HER performance [24,25] and have proven to be alternatives for Pt-based electrocatalysiso ft he HER. In particular, MoSe 2 represents ap romising non-noble-metalbased electrocatalyst and has one of the best-known HER performance in media.…”

Recent advances in two‐dimensional transition metal dichalcogenides as photoelectrocatalyst for hydrogen evolution reaction

“…Besides, MoS 2 , MoS 2 , WS 2, and WSe 2 have also been engineered in terms of increasing the defects through crumbling the large materials into small particles or doping foreign element into the lattice of TMDs such as metal dopant or S dopant. [137][138][139][140][141][142][143] Nevertheless, the number of publications about these surface modification and defect engineering on TMDs for PEC-HER is still limited. The unstable state of TMD surface due to the defects generally resulted in the short durability of catalyst under working condition, therefore, it still needs more practical and theorical methods to solve this problem.…”