Design And Controllable Synthesis Of Molybdenum-based Nanomaterials By Electronic Structure Modulation Engineering For Highly Efficient Electrocatalytic Performance

With the rapid development of global economy,energy demand and consumption have increased dramatically.Excessive exploitation of fossil fuels not only causes energy exhaustion,but also brings extremely serious pollution to the environment.Hydrogen,with high energy density and carbon-free,has attracted widespread attention.Hydrogen production by water electrolysis has been considered as the most promising approach,which has advantages of simple preparation process,wide reactant sources,low cost,environmental friendly.Currently,the state-of-the-art catalysts for hydrogen production by electrolytic water are still the precious-metal-based materials.However,the limited resource and high price of these noble metal catalysts seriously impede their widespread in commercial applications.The content of molybdenum is relatively abundant on earth,and molybdenum-based nanomaterials have unique electronic structures and exhibit excellent electrochemical properties,which are potential candidate to replace precious metal materials.In view of the poor conductivity,fewer surface active sites,and inferior intrinsic catalytic activity of the molybdenum-based catalyst,we mainly focused on constructing molybdenum-based electrocatalysts by regulating the electronic structure of nanomaterials combining with theoretical calculation and experimental synthesis strategy.The influence of electronic structure and material morphology on catalytic performances was studied to realize the controllable synthesis of high efficient catalyst for hydrogen production.The main research contents are as follows:?1?Nitrogen-decorated dual transition metal sulphide heterostructures nanomaterials for highly efficient hydrogen evolution in alkaline electrolytesA novel nitrogen-decorated dual transition metal sulphide heterostructures electrocatalyst?N-NiS/MoS₂?was constructed with an enhanced hydrogen evolution reaction?HER?performance in alkaline electrolytes.The novel N-NiS/MoS₂heterostructures exhibited highly efficient electrocatalytic activity and favorable stability.Combining with the results of density functional theory?DFT?calculations and X-ray photoelectron spectroscopy?XPS?,we confirmed that the introduction of nitrogen can effectively tune the electronic structure of NiS and MoS₂.Furthermore,the synergistic effect between dual-active components N-NiS and N-MoS₂ in the N-NiS/MoS₂ heterostructures effectively promoted water dissociation and hydrogen formation,leading to remarkable increase of HER performance in alkaline medium.?2?Strong electronic couple engineering of transition metal phosphides-oxides heterostructures as multifunctional electrocatalyst for hydrogen productionBased on the work?1?,we adopted the selective phosphorization strategy by controlling the only phosphorization of higher activity Ni atoms in precursor to construct Ni₂P/MoO₂/NF heterostructures nanorods arrays?Ni₂P/MoO₂/NF HNRs?electrocatalyst.The in situ conversion of precursor conduces to the formation of intimate interfaces,contributing to the strong electronic coupling between Ni₂P and MoO₂.By effective interface construction,the strong electronic coupling effect is induced by spontaneously electron transfer across Ni₂P/MoO₂ heterointerface,which modulates the electronic structure and enhances intrinsic catalytic activity,leading to outstanding electrocatalytic activities and long-time durability in alkaline electrolytes.Impressively,when coupled Ni₂P/MoO₂/NF HNRs for urea-assisted electrolyzer,the potential as low as 1.35 V is needed to achieve 10 mA·cm^-2.Experimental and density functional theory results reveal that the strong electronic coupling effect enhances the synergy effect between Ni₂P and MoO₂,beneficial for boosting the H₂ production.?3?Three-dimensional reticular hierarchical electrocatalyst of bimetal phosphide nanosheets for overall water splittingThe bimetal phosphide electrocatalyst?MoCoP-NF?with ultrathin nanosheets was successfully prepared by in situ synthesis.The MoCoP-NF electrocatalyst with a three-dimensional reticular hierarchical structure exhibited excellent electrocatalytic hydrogen evolution and oxygen evolution performance under alkaline condition.The three-dimensional reticular hierarchical structure composed of ultra-thin nanosheets not only increase the specific surface area of the electrocatalyst,expose more active sites,promote penetration of electrolyte to electrode surface during the electrocatalysis process,but also facilitate electron transfer and improve the catalytic reaction dynamics.In addition,the molybdenum can adjust the electronic structure of cobalt phosphide and enhance the essential electrocatalytic activity of the catalyst.Density functional theory simulations reveal that the synergistic effect between molybdenum phosphide and cobalt phosphide improves its electrocatalytic performance under alkaline conditions.?4?Regulating the electronic structure of MoP with ultralow Ru doping as efficient catalysts for hydrogen evolution reactionThe theoretical calculations results of work?2?and work?3?indicated that the interaction between molybdenum and phosphorus interface in the nanostructure is the best active site for catalytic hydrogen evolution.Therefore,we performed DFT calculations to study the hydrogen-evolution mechanism of molybdenum phosphide?MoP?.The results suggested that p orbital electrons of phosphorus in molybdenum phosphide play a major role in the adsorption and desorption of hydrogen.Furthermore,a small amount of ruthenium was introduced into molybdenum phosphide to modulate the electronic structure,which not only improves the intrinsic electrocatalytic hydrogen evolution activity of molybdenum phosphide,but also increases the electrocatalytic active site of the material.Based on the results of theoretical calculation,we successfully prepared nanospherical electrocatalyst of Ru/MoP/C using non-toxic phytic acid as both phosphorus and carbon sources.As expect,the catalyst showed extremely good performance for electrocatalytic hydrogen evolution under alkaline conditions.This work provides a valuable avenue for the rational design of electrocatalysts for highly efficient HER.