The electrochemical generation of hydrogen is a key enabling technology for the production of sustainable fuels. Transition metal chalcogenides show considerable promise as catalysts for this reaction, but to date there are very few reports of tellurides in this context, and none of these transition metal telluride catalysts are especially active. Here, we show that the catalytic performance of metallic 1T′-MoTe2 is improved dramatically when the electrode is held at cathodic bias. As a result, the overpotential required to maintain a current density of 10 mA cm−2 decreases from 320 mV to just 178 mV. We show that this rapid and reversible activation process has its origins in adsorption of H onto Te sites on the surface of 1T′-MoTe2. This activation process highlights the importance of subtle changes in the electronic structure of an electrode material and how these can influence the subsequent electrocatalytic activity that is displayed.

Herein, we report novel triarylamine based hole transporting materials (HTM) with high mobilities for perovskite solar cells.

The electrocatalytic hydrogen evolution reaction (HER) is of central importance for the production of H2 from sustainable sources. Currently, Pt is the best electrocatalyst for this transformation, but other materials based on less‐precious elements are now attracting increased attention. Of these alternatives, the molybdenum chalcogenides show particular promise. MoS2 has been explored extensively in this regard, which has highlighted the important role of polymorphism for catalytic activity. However, the conversion into an active polymorph is complex, and the stability of the catalyst under electrochemical conditions is poor. In contrast, MoTe2 has been barely studied as an electrocatalyst for the HER. Herein, we isolate the semiconducting and metallic polymorphs of MoTe2 using an easy solid‐state route and show that interconversion between the two polymorphs of MoTe2 can be achieved without a change in morphology by a simple temperature‐annealing protocol. Although the semiconducting form is a rather poor electrocatalyst for the HER, the metallic 1T′‐MoTe2 polymorph is an efficient and stable electrocatalyst for the HER in 1 m H2SO4. Even in the bulk form, it achieved a low overpotential with a Tafel slope of (78±4) mV dec−1 and full Faradaic efficiency. These findings highlight the importance of polymorphic control in the development of HER catalysts and suggest an efficient route for the discovery of new and improved electrocatalysts.

Two-dimensional (2D) transition-metal dichalcogenides have become promising candidates for surface-enhanced Raman spectroscopy (SERS), but currently very few examples of detection of relevant molecules are available. Herein, we show the detection of the lipophilic disease marker β-sitosterol on fewlayered MoTe 2 films. The chemical vapor deposition (CVD)grown films are capable of nanomolar detection, exceeding the performance of alternative noble-metal surfaces. We confirm that the enhancement occurs through the chemical enhancement (CE) mechanism via formation of a surface−analyte complex, which leads to an enhancement factor of ≈10 4 , as confirmed by Fourier transform infrared (FTIR), UV−vis, and cyclic voltammetry (CV) analyses and density functional theory (DFT) calculations. Low values of signal deviation over a seven-layered MoTe 2 film confirms the homogeneity and reproducibility of the results in comparison to noble-metal substrate analogues. Furthermore, β-sitosterol detection within cell culture media, a minimal loss of signal over 50 days, and the opportunity for sensor regeneration suggest that MoTe 2 can become a promising new SERS platform for biosensing.

The hydrogen evolution reaction (HER) from water is governed by electrocatalysts used. Multiple factors such as crystal structure, composition and morphology dictate the final catalytic performance. However, as multicomponent materials...

Minor structural changes in transition metal dichalcogenides can have dramatic effects on their electronic properties. This makes the quest for key parameters that enable a selective choice between the competing metallic and semiconducting phases in the 2D MoTe 2 system compelling. Herein, we report the optimal conditions at which the choice of the initial seed layer dictates the type of crystal structure of atomically-thin MoTe 2 films grown by chemical vapour deposition (CVD). When Mo metal is used as a seed layer, semiconducting 2H-MoTe 2 is the only product. Conversely, MoO 3 leads to the preferential growth of metallic 1T′-MoTe 2. The control over phase growth allows for simultaneous deposition of both 2H-MoTe 2 and 1T′-MoTe 2 phases on a single substrate during one CVD reaction. Furthermore, Rhodamine 6G dye can be detected using few-layered 1T′-MoTe 2 films down to 5 nM concentration, demonstrating surface enhanced Raman spectroscopy (SERS) with sensitivity several orders of magnitude higher than for bulk 1T′-MoTe 2 .

Minor structural changes in transition metal dichalcogenides can have dramatic effects on their electronic properties. This makes the quest for key parameters that can enable a selective choice between the competing metallic and semiconducting phases in the 2D MoTe₂ system compelling. Herein, we report the optimal conditions at which the choice of the initial seed layer dictates the type of crystal structure of atomically-thin MoTe₂ films grown by chemical vapour deposition (CVD). When Mo metal is used as a seed layer, phase-pure semiconducting 2H-MoTe₂ is the only product. Conversely, MoO₃ leads to the preferential growth of phase-pure metallic 1Tꞌ-MoTe₂. The control over phase growth allows for simultaneous deposition of both 2H-MoTe₂ and 1Tꞌ-MoTe₂ phases on a single substrate during one CVD reaction. Furthermore, Rhodamine 6G dye can be detected using few-layered 1Tꞌ-MoTe₂ films down to 5 nM concentration which is several orders of magnitude higher than the value observed for bulk 1Tꞌ-MoTe₂.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.