Constructing interfacial electric field and Zn vacancy modulated ohmic junctions ZnS/NiS for photocatalytic H_(2) evolution

Adjusting the interfacial transport efficiency of photogenerated electrons and the free energy of hydrogen adsorption through interface engineering is an effective means of improving the photocatalytic activity of semiconductor photocatalysts.Herein,hollow ZnS/NiS nanocages with ohmic contacts containing Zn vacancy(V_(Zn)-ZnS/NiS)are synthesized using ZIF-8 as templates.An internal electric field is constructed by Fermi level flattening to form ohmic contacts,which increase donor density and accelerate electron transport at the V_(Zn)-ZnS/NiS interface.The experimental and DFT results show that the tight interface and V_(Zn) can rearrange electrons,resulting in a higher charge density at the interface,and optimizing the Gibbs free energy of hydrogen adsorption.The optimal hydrogen production activity of V_(Zn)-ZnS/NiS is 10,636 μmol h^(-1) g^(-1),which is 31.9 times that of V_(Zn)-ZnS.This study provides an idea for constructing sulfide heterojunctions with ohmic contacts and defects to achieve efficient photocatalytic hydrogen production.

Defective ZnS nanoparticles anchored in situ on N-doped carbon as a superior oxygen reduction reaction catalyst

Defect engineering has been used to develop low-cost and effective catalysts to boost oxygen reduction reactions.However,the development of catalysts that use metal cation vacancies as the active sites for oxygen reduction reaction is lacking.In this study,ZnS nanoparticles on N-doped carbon serve as an oxygen reduction reaction catalyst.These catalysts were prepared via a one-step method at 900℃.Amazingly,the high-resolution transmission electron microscope image revealed obvious defects in the ZnS nanoparticles.These facilitated the catalyst synthesis,and the product displayed good electrocatalytic performance for the oxygen reduction reaction in an alkaline medium,including a lower onset potential,lower mid-wave potential,four electron transfer process,and better durability compared with 20 wt%Pt/C.More importantly,the density functional theory results indicated that using the Zn vacancies in the prepared catalyst as active sites required a lower reaction energy to produce OOH*from*OO toward oxygen reduction reaction.Therefore,the proposed catalyst with Zn vacancies can be used as a potential electrocatalyst and may be substitutes for Pt-based catalysts in fuel cells,given the novel catalyst’s resulting performance.

Room temperature ferromagnetism of boron-doped ZnO nanoparticles prepared by solvothermal method

In this study, B-doped ZnO nanoparticles were synthesized by template-free solvothermal method. X-ray diffraction analysis reveals that B-doped ZnO nanoparti- cles have hexagonal wurtzite structure. Field emission scanning electron microscopy observations show that the nanoparticles have a diameter of 50 nm. The room tem- perature ferromagnetism increases monotonically with increasing B concentration to the ZnO nanoparticles and reaches the maximum value of saturation magnetization 0.0178 A.ma.kg-1 for 5 % B-doped ZnO nanoparticles. Moreover, photoluminescence spectra reveal that B doping causes to produce Zn vacancies （Vzn）. Magnetic moment of oxygen atoms nearest to the B-Vzn vacancy pairs can be considered as a source of ferromagnetism for B-doped ZnO nanoparticles.