Due to its great efficiency, the electrocatalytic nitrogen reduction reaction (NRR) presents itself as a viable and eco-friendly substitute for the traditional Haber-Bosch ammonia production process. ...However, it is still a formidable task to find electrocatalysts with high activity and selectivity. In this study, a series of transition metals (TM = Ti–Ni, Zr–Mo, Ru–Pd, and Hf–Pt) anchored on 1T′-dual-transition-metal dichalcogenides (1T′-d-TMDs) monolayers (TM2@1T′-CrCoS4) were systematically investigated as electrocatalysts for NRR using first-principles calculations based on density functional theory. Based on a thorough examination of selectivity, high activity, and stability, Mn2@1T′-CrCoS4 and Co2@1T′-CrCoS4 demonstrate exceptional NRR performance. With a limiting potential of −0.11 V, Mn2@1T′-CrCoS4 stood out among them in terms of catalytic activity, favoring the enzymatic pathway. Furthermore, ab initio molecular dynamics (AIMD) simulations were used to assess the dynamic stability of Mn2@1T′-CrCoS4 and Co2@1T′-CrCoS4. To determine the source of increased activities, the density of states (DOS), charge density difference, and crystal orbital Hamilton population analysis were used. According to our research, the 1T′-d-TMDS is a viable substrate for the development of effective NRR catalysts and offers a platform for electrocatalyst experimentation.
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•1T′-d-TMDs monolayers have been investigated as a new efficient electrocatalyst substitute in the electrocatalysis field.•The 1T′-CrCoS4 with unique characteristics is potential electrocatalysis as the candidate material for NRR.•The NRR catalytic performance of TM dimer anchored on 1T′-CrCoS4 is investigated.•The Mn2@1T′-CrCoS4 exhibits excellent catalytic activity with a low limiting potential of −0.11 V.
A thermodynamic descriptor-based approach using density functional theory calculations was used to investigate the activity and stability of 26 different transition metal dichalcogenide catalysts for ...the hydrogen evolution reaction (HER). We considered variations in the transition metal (Ti, V, Nb, Ta, Mo, W, Pd, Pt), the chalcogen (S and Se), the crystal structure (1T and 2H), and the surface termination (basal plane or edge). We find that the HER activity is strongly related to the stability of the catalyst, setting practical limitations on their potential application in HER. For the basal planes, the metallicity is found to be the most important parameter in determining the activity rather than structure or composition. However, systematic improvements in activity are strongly limited by a decrease in stability. For the edges, the activity and stability relationship are similar regardless of structure or chalcogen, and it is possible to achieve optimal hydrogen binding with a stable surface. Nudged elastic band calculations were carried out to probe the possible mechanisms for HER; the insurmountably high barrier for the Tafel mechanism suggests that HER may occur solely via the Volmer–Heyrovsky route for these materials.
•The hydrogen evolution reaction on various layered transition metal dichalcogenides have been investigated using density functional theory.•The effect of the composition, structure, and facet are elucidated in terms of activity and stability.•The Volmer–Tafel route is shown to be unlikely on either basal planes or edges of the transition metal dichalcogenides.
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•Mechanism of sliding grain boundary formation in 1T’-WTe2.•Studying the sliding grain boundaries in 1T’-WTe2 through atomic scale analysis.•Modeling of sliding grain boundaries in ...1T’-WTe2 through sliding and rotation.•Sliding grain boundaries exhibit metallic features in the local density of states.•Formation energy calculated by DFT shows stability of grain boundaries.
Understanding the complexity of grain boundaries between domains is essential for controlling material properties. While grain boundaries in two-dimensional (2D) materials have revealed a few cases of unique features with chemical reactivity and electronic structures, the intriguing case of one-dimensional (1D) grain boundaries still remains relatively unexplored, in particular, for non-hexagonal structures. Here, sliding grain boundary formation in 1T’-WTe2 has been investigated at the atomic scale. We found that the grain boundary keeps W-Te zigzag atomic rows in one direction. The asymmetric 1D sliding grain boundary formations exhibited an angle of 38° relative to the W-Te zigzag atomic rows, strain near the sliding grain boundary formation, and fluctuations in the local density of states (LDOS). The electronic structure in the asymmetric 1D sliding grain boundary formation shows two-line features in LDOS mapping. The structural models under the directional constraint were constructed with two symmetry operations, sliding and 180°-rotation, which agree well with the experimental results. Calculation of formation energy for the models suggested that the grain boundary formation was formed by 180°-rotated domains meeting during their growth along with sliding. The understanding of the sliding grain boundary formation provides a promising path to chemical applications such as hydrogen evolution reactions.
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•We report machine-learning-empowered RHEED analysis of MoSe2 thin films.•In situ RHEED provides real-time information during 2D thin film growth.•Principal component analysis ...distinguishes between the film and substrate signals.•Modified PCA discriminates variation of initial growth modes.
In situ reflection high-energy electron diffraction (RHEED) is a powerful technique for monitoring surface states and offers invaluable insights into thin film growth. However, extracting hidden features and subtle changes from its vast data remains as a challenge. This work bridges the gap by employing machine learning (ML)-empowered RHEED analysis to elucidate the growth dynamics of two-dimensional (2D) transition metal dichalcogenide (TMDC) thin films grown under two distinct growth modes. Principal component analysis (PCA) and its modified processes were used to separate contributions of the graphene substrate and the MoSe2 film in the RHEED video. The ML-empowered RHEED analysis allowed us to effectively filter out the strong substrate signal and reconstructing RHEED videos solely for the MoSe2 films. This approach enabled detailed monitoring of film growth with unique features, and clearly distinguishing between the layer-by-layer growth mode and the island one. This work demonstrates the potentials of ML-empowered RHEED analysis for revealing complex growth dynamics of 2D TMDC materials, paving the way for advanced thin film monitoring and autonomous control in wider scope of thin film technologies.
In a recent publication 2D Materials, 8, 045033 (2021), it was reported that the growth of a monolayer PdTe2 in ultra-high vacuum could be achieved by deposition of tellurium on a palladium (111) ...crystal surface and subsequent thermal annealing. By means of low-energy electron diffraction intensity (LEED-IV) structural analysis, we show that the obtained 3×3R30° superstructure is in fact a TePd2 surface alloy. Attempts to produce a PdTe2 layer in ultra-high vacuum by increasing the Te content on the surface were not successful.
•In UHV, Te reacts with Pd(111) forming a well-ordered Pd2Te surface alloy.•The Pd2Te surface alloy is stable against thermal decomposition up to 1070K.•The growth of a PdTe2 surface layer as reported earlier could not be confirmed.
Generating electron coherence in quantum materials is essential in optimal control of many-body interactions and correlations. In a multidomain system this signifies nonlocal coherence and emergence ...of collective phenomena, particularly in layered 2D quantum materials possessing novel electronic structures and high carrier mobilities. Here we report nonlocal ac electron coherence induced in dispersed MoS₂ flake domains, using coherent spatial self-phase modulation (SSPM). The gap-dependent nonlinear dielectric susceptibilityχ
(3)measured is surprisingly large, where direct interband transition and two-photon SSPM are responsible for excitations above and below the bandgap, respectively. A wind-chime model is proposed to account for the emergence of the ac electron coherence. Furthermore, all-optical switching is achieved based on SSPM, especially with two-color intraband coherence, demonstrating that electron coherence generation is a ubiquitous property of layered quantum materials.
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