Molybdenum disulfide (MoS2) in its two-dimensional (2D) morphology has favorable catalytic properties for the hydrogen evolution reaction (HER). To fully take advantage of this capability and in order to enhance this material’s HER performance, viable methods for synthesizing and tuning electronic properties of 2D MoS2 should be developed. Here, we demonstrate a facile and nonhazardous approach to partially intercalate Li+ ions into the 2D MoS2 host structure. We show that such an intercalation is possible in a nonhazardous saline Li+ containing solution using a grinding/sonication-assisted exfoliation method in both dark and simulated sun irradiation conditions. A partial phase transformation from semiconducting (2H) to metallic (1T) phase is observed for the majority of flakes, after the process. We observe a notable enhancement of the HER activity for samples prepared under light illumination in the presence of a Li+ containing solution, in comparison to both pristine 2D MoS2 samples and samples processed in the dark. This method provides an effective approach for phase engineering of 2D MoS2 for enhancing its HER performance.

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The cooling behavior of GaN‐on‐diamond substrate can be enhanced by reducing the thermal boundary resistance (TBR), which is mainly determined by the nature of interlayer. Although SiN film is considered as the primary candidate of dielectric layer, it is still needed to be optimized. In order to facilitate the understanding of the influence of dielectric layer on the TBR of GaN‐on‐Diamond substrate, aluminum nitride (AlN), and silicon nitride (SiN) film were compared systematically, both of which are 100 nm. The time‐domain thermoreflectance (TDTR) measurements, adhesion evaluation, and microstructural analysis methods were adopted to analyse these two interlayers. The results show the TBR of SiN interlayer is as low as 38.5 ± 2.4 m2K GW−1, comparing with the value of 56.4 ± 5.5 m2K GW−1 for AlN interlayer. The difference of TBR between these two interlayers is elucidated by the diamond nucleation density, and the adhesion between the diamond film and GaN substrate, both of which are affected by the surface charge and chemical groups of the dielectric layer.

As we know that more effective sy nthesis of diamond combined with physical and chemical properties of hydrogen termination in aqueous environment as well as device structure design can greatly facilitate the chemical and electrochemical applications of higher cost-performance diamond. For this purpose, the direct-current(DC)characteristics, surface reactionand reparation of a hydrogen-terminated DC arc jet plasma CVD polycrystalline diamond, which hasa high cost-performance, were characterized by I-V experimentsbased on aFET-like structure device in multipleaqueoussolutions.The variation trends of the I-Vproperties of device based on pH were similar indifferent aqueous solutionsbut could be affected by disparate ions (such as K + ions)or organic molecules(such as citric acid radicalsora benzene ring).Especially, owing to the founded replacement of hydrogen termination with hydroxyl (-OH),carboxyl radical (-COOH)or carbon-oxygen bond (-C-O-C-) in mixed solution, i.e.,KHP+ H 2 SO 4 (and +NaOH) solutions, the resistance of the device was remarkably increased from 13.57kΩto 95.78kΩ.However, the raised resistance of surface reacted diamond (SRD) can be reducedprominentlyby repairing hydrogenterminationthroughnegative potential sweeps (NPS)at a low negative potential (-1 to -3 V) ifthe SRDwas introduced as an electrode in a strong inorganic acid.What's more, the NPS repaireddevice, whichsubsequently stored for four weeks, wasmore sensitive than the original hydrogen plasma-treated diamond in aqueoussolution environments. This repaired resultwascoming out of NPS re-formed C-H bonds with higher intensity. These findings will be the references of failure and reparationof diamond hydrogen termination inaqueous environment.