: Uniform growth of pristine two dimensional (2D) materials over large areas at lower temperatures without sacrifice of their unique physical properties is a critical pre-requisite for seamless integration of next-generation van der Waals heterostructures into functional devices. This Letter describes a vapor phase growth technique for precisely controlled synthesis of continuous, uniform molecular layers of MoS2 on silicon dioxide and highly oriented pyrolitic graphite substrates of over several square centimeters at 350 deg C. Synthesis of few-layer MoS2 in this ultra-high vacuum physical vapor deposition process yields materials with key optical and electronic properties identical to exfoliated layers. The films are composed of nano-scale domains with strong chemical binding between domain boundaries, allowing lift-off from the substrate and electronic transport measurements from contacts with separation on the order of centimeters.

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Continuous Ultra-Thin MOS2 Films Grown by Low-Temperature Physical Vapor Deposition (Postprint)

Magnetron sputtering enabled sustainable synthesis of nanomaterials for energy electrocatalysis

The generation of clean energy is necessary for future technological developments. The utilization of solar illumination to produce H2 from water electrolysis is an alternative route to address the issue. However, the reaction is a thermodynamically uphill task. Furthermore, designing a photocathode, which can use most of the incident radiation for the photoelectrochemical (PEC) reaction, plays an important role. Surface-modified p-Si can be an economically viable option. The sluggish electro-kinetics on the Si surface has been rectified with coatings of cocatalyst materials. In the current review, we have discussed the possible modifications performed on the p-Si surface to reduce the loss due to reflection and coating of the cocatalyst, e.g. MoS2 on p-Si to improve H2 evolution. The facile charge carrier kinetics at the electrode–electrolyte interface has also been discussed. The development of cocatalysts has been focused on our previous experience for two decades. From surface plasmon resonance to heteroatom doping, that is, intentional defect formation and heterostructure design, we have included a comprehensive discussion on cocatalysts. The energetics of single atom replacement and its implications for efficiency has been included. This review gives insights into the currently emerging cocatalyst design for PEC water splitting. In this regard, the review presents insights into the phase transformation in MoS2 during the PEC process using operando techniques. A discussion on the effect of single atom replacement in the inactive basal-MoS2 plane has been included.

Comprehensive view on recent developments in hydrogen evolution using MoS2 on a Si photocathode: from electronic to electrochemical aspects

Nitric oxide electroreduction reaction (NOER) is an efficient method for NH3 synthesis and NOx-related pollutant treatment. However, current research on NOER catalysts mainly focuses on noble metals and single atom catalysts, while low-cost transition metal dichalcogenides (TMDCs) are rarely considered. Herein, by applying density functional theory (DFT) calculations, we study the catalytic performance of NOER over 2H-MoS2 monolayers with the most common S vacancies and some Mo atoms substituted by transition metal atoms (denoted as TM-MoS2@VS). Our results show that an S vacancy and a heteroatom substitution tend to form a first nearest neighbour (1NN) pair, which greatly improves the NOER catalytic performance of 2H-MoS2. The S vacancy site can trigger NOER by strongly adsorbing a NO molecule and elongating the NO bond, while the heteroatom dopant can assist NOER by tuning the electron donating capability of 2H-MoS2 which breaks the linear scaling relations among key reaction intermediates. At low NO coverage, NH3 can be correspondingly yielded at -0.06 and -0.38 V onset potentials over the Pt- and Au-doped MoS2 catalysts with S vacancies (Pt-MoS2@VS and Au-MoS2@VS). At high NO coverage, N2O/N2 is thermodynamically favored. Meanwhile, the competing hydrogen evolution reaction (HER) is suppressed. Thus, the Pt-MoS2@VS catalysts are promising candidates for NOER. In addition, coupling the substitutional doping of Mo atoms to S vacancies presents great potential in improving the catalytic activity and selectivity of MoS2 for other reactions. In general, the strategy of coupling hetero-metal doping and chalcogen vacancy can be extended to enhance the catalytic activity of other TMDCs.

Vacancy-triggered and dopant-assisted NO electrocatalytic reduction over MoS2.

NO Electroreduction by Transition Metal Dichalcogenides with Chalcogen Vacancies

The availability and catalytic activity of the cost-efficient electrocatalysts are the dominant factors for the hydrogen evolution reaction (HER) performance in the renewable hydrogen economy. Exte...

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Zewen Duan

Papers

Constructing Mono-/Di-/Tri-Types of Active Sites in MoS2 Film toward Understanding Their Electrocatalytic Activity for the Hydrogen Evolution