Identifying effective means to improve the electrocatalytic performance of transition metal dichalcogenides in alkaline electrolytes is a significant challenge. Herein, an advanced electrocatalyst possessing shells of molybdenum disulfide (MoS2) on molybdenum carbide (Mo2C) for efficient electrocatalytic activity in alkaline electrolytes is reported. The strained sheets of curved MoS2 surround the surface of Mo2C, turning the inactive basal planes of MoS2 into highly active electrocatalytic sites in the alkaline electrolyte. The van der Waals layers, which even possess van der Waals epitaxy along (100) facets of MoS2 and Mo2C, enhance the spin coupling between MoS2 and Mo2C, providing an easy electron transfer path for excellent electrocatalytic activity in alkaline electrolytes and solving the stability issue. In addition, it is found that curved MoS2 sheets on Mo2C show 3.45% tensile strain in the lattice, producing excellent catalytic activity for both oxygen reduction reaction (ORR) (with E1/2 = 0.60 V vs RHE) and oxygen evolution reaction (OER) (overpotential = 1.51 V vs RHE at 10 mA cm−2) with 60 times higher electrochemical active area than pristine MoS2. The unique structure and synthesis route outlined here provide a novel and efficient approach toward designing highly active, durable, and cost‐effective ORR and OER electrocatalysts.

Despite many encouraging properties of transition metal dichalcogenides (TMDs), a central challenge in the realm of industrial applications based on TMD materials is to connect the large‐scale synthesis and reproducible production of highly crystalline TMD materials. Here, the primary aim is to resolve simultaneously the two inversely related issues through the synthesis of MoS2(1−x )Se2x ternary alloys with customizable bichalcogen atomic (S and Se) ratio via atomic‐level substitution combined with a solution‐based large‐area compatible approach. The relative concentration of bichalcogen atoms in the 2D alloy can be effectively modulated by altering the selenization temperature, resulting in 4 in. scale production of MoS1.62Se0.38, MoS1.37Se0.63, MoS1.15Se0.85, and MoS0.46Se1.54 alloys, as well as MoS2 and MoSe2. Comprehensive spectroscopic evaluations for vertical and lateral homogeneity in terms of heteroatom distribution in the large‐scale 2D TMD alloys are implemented. Se‐stimulated strain effects and a detailed mechanism for the Se substitution in the MoS2 crystal are further explored. Finally, the capability of the 2D alloy for industrial application in nanophotonic devices and hydrogen evolution reaction (HER) catalysts is validated. Substantial enhancements in the optoelectronic and HER performances of the 2D ternary alloy compared with those of its binary counterparts, including pure‐phase MoS2 and MoSe2, are unambiguously achieved.

The performances of organic electronic and/or photonic devices rely heavily on the nature of the inorganic/organic interface. Control over such hybrid interface properties has been an important issue for optimizing the performances of polymer solar cells bearing metal-oxide conducting channels. In this work, we studied the effects of an interfacial atomic layer in an inverted polymer solar cell based on a ZnO nanorod array on the device performance as well as the dynamics of the photoexcited carriers. We adopted highly conformal TiO2 interfacial layer using plasma enhanced atomic layer deposition (PEALD) to improve the compatibility between the solution-prepared active layer and the ZnO nanorod array. The TiO2 interfacial layer facilitated exciton separation and subsequent charge transfer into the nanorod channel, and it suppressed recombination of photogenerated carriers at the interface. The presence of even 1 PEALD cycle of TiO2 coating substantially improved the short-circuit current density (Jsc), open circuit voltage (Voc), and fill factor (FF), leading to more than 2-fold enhancement in the power conversion efficiency (PCE). The dynamics of the photoexcited carriers in our devices were studied using transient absorption (TA) spectroscopy. The TA results clearly revealed that the TiO2 coating played a key role as an efficient quencher of photogenerated excitons, thereby reducing the exciton lifetime. The electrochemical impedance spectra (EIS) provided further evidence that the TiO2 atomic interfacial layer promoted the charge transfer at the interface by suppressing recombination loss.

In order to combine advantages of ZnO thin film transistors (TFTs) with a high on-off ratio and graphene TFTs with extremely high carrier mobility, we present a facile methodology for fabricating ZnO thin film/graphene hybrid two-dimensional TFTs. Hybrid TFTs exhibited ambipolar behavior, an outstanding electron mobility of 329.7 ± 16.9 cm2/V·s, and a high on-off ratio of 105. The ambipolar behavior of the ZnO/graphene hybrid TFT with high electron mobility could be due to the superimposed density of states involving the donor states in the bandgap of ZnO thin films and the linear dispersion of monolayer graphene. We further established an applicable circuit model for understanding the improvement in carrier mobility of ZnO/graphene hybrid TFTs.

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