The van der Waals heterostructures have evolved as novel materials for complementing the Si-based semiconductor technologies. Group-10 noble metal dichalcogenides (e.g., PtS₂, PtSe₂, PdS₂, and PdSe₂) have been listed into two-dimensional (2D) materials toolkit to assemble van der Waals heterostructures. Among them, PdSe₂ demonstrates advantages of high stability in air, high mobility, and wide tunable bandgap. However, the regulation of p-type doping of PdSe₂ remains unsolved problem prior to fabricating p–n junction as a fundamental platform of semiconductor physics. Besides, a quantitative method for the controllable doping of PdSe₂ is yet to be reported. In this study, the doping level of PdSe₂ was correlated with the concentration of Lewis acids, for example, SnCl₄, used for soaking. Considering the transfer characteristics, the threshold voltage (the gate voltage corresponding to the minimum drain current) increased after SnCl₄ soaking treatment. PdSe₂ transistors were soaked in SnCl₄ solutions with five different concentrations. The threshold voltages from the as-obtained transfer curves were extracted for linear fitting to the threshold voltage versus doping concentration correlation equation. This study provides in-depth insights into the controllable p-type doping of PdSe₂. It may also push forward the research of the regulation of conductivity behaviors of 2D materials.

Transition metal nitride/carbide (TMN/C) have been actively explored as low-cost hydrogen evolution reaction (HER) electrocatalysts owing to their Pt-like physical and chemical properties. Unfortunately, pure TMN/C suffers from strong hydrogen adsorption and lacks active centers for water dissociation. Herein, we developed a switchable WO₃-based in situ gas–solid reaction for preparing sophisticated Fe-N doped WC and Fe-C doped WN nanoarrays. Interestingly, the switch of codoping and phase can be effectively manipulated by regulating the amount of ferrocene. Resultant Fe-C-WN and Fe-N-WC exhibit robust electrocatalytic performance for HER in alkaline and acid electrolytes, respectively. The collective collaboration of morphological, phase and electronic effects are suggested to be responsible for the superior HER activity. The smallest |ΔG_H*| value of Fe-N-WC indicates preferable hydrogen-evolving kinetics on the Fe-N-WC surface for HER under acid condition, while Fe-C-WN is suggested to be beneficial to the adsorption and dissociation of H₂O for HER in alkaline electrolyte.

Electrocatalytic hydrogen production in alkaline media is extensively adopted in industry. Unfortunately, further performance improvement is severely impeded by the retarded kinetics, which requires the fine regulation of water dissociation, hydrogen recombination, and hydroxyl desorption. Herein, we develop a multi-interface engineering strategy to make an elaborate balance for the alkaline hydrogen evolution reaction (HER) kinetics. The graphene cross-linked three-phase nickel sulfide (NiS-NiS₂-Ni₃S₄) polymorph foam (G-NNNF) was constructed through hydrothermal sulfidation of graphene wrapped nickel foam as a three-dimensional (3D) scaffold template. The G-NNNF exhibits superior catalytic activity toward HER in alkaline electrolyte, which only requires an overpotential of 68 mV to drive 10 mA·cm⁻² and is better than most of the recently reported metal sulfides catalysts. Density functional theory (DFT) calculations verify the interfaces between nickel sulfides (NiS/NiS₂/Ni₃S₄) and cross-linked graphene can endow the electrocatalyst with preferable hydrogen adsorption as well as metallic nature. In addition, the electron transfer from Ni₃S₄/NiS₂ to NiS results in the electron accumulation on NiS and the hole accumulation on Ni₃S₄/NiS₂, respectively. The electron accumulation on NiS favors the optimization of the H* adsorption, whereas the hole accumulation on Ni₃S₄ is beneficial for the adsorption of H₂O. The work about multi-interface collaboration pushes forward the frontier of excellent polymorph catalysts design.