21:T50e,Monolayer MoS₂ has attracted much attention due to its high on/off current ratio, transparency, and suitability for optoelectronic devices. Surface doping by molecular adsorption has proven to be an effective method to facilitate the usage of MoS₂. However, there are no works available to systematically clarify the effects of the adsorption of F₄TCNQ, PTCDA, and tetracene on the electronic and optical properties of the material. Therefore, this work elucidated the problem by using density functional theory calculations. We found that the adsorption of F₄TCNQ and PTCDA turns MoS₂ into a p-type semiconductor, while the tetracene converts MoS₂ into an n-type semiconductor. The occurrence of a new energy level in the conduction band for F₄TCNQ and PTCDA and the valence band for tetracene reduces the bandgap of the monolayer MoS₂. Besides, the MoS₂/F₄TCNQ and MoS₂/PTCDA systems exhibit an auxiliary optical peak at the long wavelengths of 950 and 850 nm, respectively. Contrastingly, the MoS₂/tetracene modifies the optical spectrum of the monolayer MoS₂ only in the ultraviolet region. The findings are in good agreement with the experiments.22:T487,Improving the slow kinetics of the oxygen reduction reaction (ORR) on the cathode of the proton exchange membrane fuel cells to achieve the performance at a practical level is an important task. PdCo alloys appeared as a promising electrocatalyst. Much attention has been devoted to the study of the effects of the Co content on the ORR activity of PdCo films and PdCo/C nanoparticles where the Co atoms can be at the topmost surface layer. While Pd-skin/PdCo alloys with the topmost layer formed only by Pd have been proved to provide a very high ORR activity and high durability, no researches are available in the literature for the effects of the Co content on the ORR activity of Pd-skin/PdCo alloys. Hence, the effects of the Co content on the ORR activity of Pd-skin/PdCo alloys are clarified in this work by using the density functional theory calculations and Nørskov’s thermodynamic model. Our results predicted that the ORR activity increases monotonically with the increase of the Co content. This behavior is particularly different compared to the Volcano behavior previously obtained in the literature for PdCo films and PdCo/C nanoparticles.23:T49d,We present a systematic investigation of polyethylenimine (PEI) doping mechanism and its effects on the multilayer MoS 2 field effect transistors (FETs). The threshold voltages of MoS 2 FETs before (i.e., pristine) and PEI doping are observed at 3.7 and 0.72 V, respectively. This negative threshold voltage shift clearly reveals that the PEI molecules effectively act as n‐type dopants. The electrical properties are improved by absorption of PEI molecules onto MoS 2 channel because the width of Schottky barrier (SB) is narrowed by the induced interfacial dipole between PEI molecules and MoS 2 layers. Through the density function theory (DFT) calculation and X‐ray photoelectron spectroscopy (XPS) analysis, we confirm that formation of MoN bond generates new energy state into the bandgap. Consequently, the hole carriers can easily tunnel through the barrier under negative gate voltage. Furthermore, PEI doping improve photoresponsivity and time‐resolved photo‐switching characteristics because of the new energy state. Our studies demonstrate the PEI doping method has a great potential for improving electrical and optical properties of MoS 2 ‐based devices.

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