Preparation And Hydrogen Evolution Properties Of Palladium-doped Molybdenum Disulfide/black Phosphorus Two-dimensional Van Der Waals Heterojunction

Hydrogen energy is a clean and efficient energy carrier,while electrocatalytic water splitting technology driven by renewable electrical energy can serve as a green and sustainable route for hydrogen energy acquisition.Molybdenum disulfide（MoS₂）is promising as a water catalyst for electrolyses with a wide range of sources and excellent performances.Compared with the 2H-phase MoS₂ of semiconductor nature,the metallic 1T-phase MoS₂（1T-MoS₂）theoretically has higher hydrogen evolution activity,but 1T-MoS₂ is mainly prepared by alkali metal intercalation and peeling,and the resulting product has a relatively lamellar structure.Completeness,lack of sufficient defects and edge active sites,resulting in the hydrogen evolution performance of 1T-MoS₂ has not been fully utilized.Aiming at this problem,this paper introduces more defect sites on the basal plane of 1T-MoS₂ through metal atom doping to enhance the electrocatalytic performance synergistically by constructing a two-dimensional van der Waals heterojunction of 1T-MoS₂ with black phosphorene,and investigates the photoelectrocatalytic hydrogen evolution performance and related catalytic mechanism of the resulting heterojunction under visible light enhancement.The specific findings are as follows:（1）Starting from the as obtained 1T-MoS₂ nanosheets exfoliated from the alkali metal intercalation,we successfully introduced s vacancy defects with hydrogen evolution activity on the 1T-MoS₂ basal plane by replacing Mo atoms in MoS₂ via palladium（Pd）atoms under mild conditions,and obtained a series of Pd doped MoS₂catalysts with high 1T phase content（Pd-1T-MoS₂）.The effect law of the doping amount of Pd atoms on the hydrogen evolution activity was investigated,The results show that 1 wt%of Pd atoms can effectively enhance the catalytic activity of the 1T-MoS₂ base surface.When the exchange current density is 10 m A cm^-2（η10）,the overpotential is 281 m V,and the Tafel slope is 122 m V dec^-1.（2）A two-dimensional van der Waals heterojunction（Pd-1T-MoS₂/BP）based on Pd-1T-MoS₂ and black phosphorous（BP）nanosheets was prepared by electrostatic self-assembly method.Theoretical calculations and experiments show that the electrons of black phosphorene will be injected into the surface of Pd-1T-MoS₂ through the heterogeneous interface,which stabilizes the 1T phase structure of Pd-1T-MoS₂ and improves the free energy of hydrogen adsorption of sulfur vacancies.The overpotential is 176 m V atη10,and the Tafel slope is only 98 m V dec-1.Pd-1T-MoS₂/BP under visible light irradiation>420 nm,the overpotential ofη10 is 97 m V,and the Tafel slope is only 66 m V dec-1,indicating that the heterojunction generates photo-generated electrons under visible light irradiation,which further improves the performance of electrocatalytic hydrogen evolution.