Construction Of Nickel-Based Nano-heterostructures For Alkaline Hydrogen Evolution

Hydrogen is considered as a promising clean and sustainable energy source for future society.Electrolysis of water is an easy and eco-friendly way to produce H2,the efficiency of which is determined by the activity and the cost of the catalyst.Therefore,the development of high-efficiency,and low-cost electrocatalysts is essential for renewable energy systems.Considering the adopted noble-metal-free catalyst on the anode and the corrosion resistance of the equipment,the industrial production of hydrogen is carried out in an alkaline environment.However,compared to acidic solutions,the hydrogen evolution reaction(HER)in alkaline solution often shows a sluggish kinetics,which hindered the efficiency improvement of the electrolyzer.Hence,seeking for low-cost and productive alkaline HER catalysts has drawn much attention in the field of materials research.Recently,several strategies have been employed to promote the activity of the electrocatalysts,including control of crystal facets,alloying,heteroatom doping,defect engineering and interfacial engineering.In addition,a series of theoretical calculation methods have been developed to understand the interaction between reactants and catalysts,especially to simulate the intermediate adsorption process.For the basic HER that contains two steps of water cleavage and hydrogen coupling,existing catalysts are difficult to provide ideal active sites for both steps.Constructing a double-site catalyst holds the promise to solve this issue.However,challenges still remain in design of dual-site catalysts:1)how to reduce the content of precious metals to reduce the cost of a catalyst?2)How to construct abundant heterogeneous interfaces to provide more active sites?3)How to optimize the electronic structure of different sites in the heterostructure to further improve the performance of alkaline HER?In response to the above problems,this thesis reports the introducing of different heteroatoms in nickel-based materials to construct nickel-based dual-site catalyst for basic HER.The catalytic performance was further enhanced by tuning the electronic configurations of both sites.1.We successfully prepared V oxide modified NiPt alloy nanomaterials(V-NiPt).This V-NiPt alloy shows abundant Pt atom edge sites on the surface anddisplays boosted catalytic activity for alkaline HER.With a Pt content of merely 3 at.%,the V-NiPt catalyst delivers a current density of 10 mA/cm2 with an ultra-low overpotential of 6 mV.XAFS measurements and DFT calculations show that the abundant surface edge Ni-Pt atoms in the V-NiPt catalyst have nearly ideal absorption energy for the intermediates in basic HER,which makes the V-NiPt catalyst an amazing catalytic activity in alkaline environment.2.We synthesized a nickel-molybdenum based bimetal metal/oxide(NiMo-M/O)heterostructure for HER catalysts in alkaline solution.The introducing of Mo species helps the formation of abundant metal/oxide interfaces on the catalyst,and regulates the electronic structure of Ni atoms substantially,thus provides ideal active sites for alkaline HER.The HER activity of NiMo-M/O in alkaline solution is even superior to that of the commercial Pt/C(10%),and a low overpotential of 26 mV is needed to drive the current density of 10 mA/cm2.Theoretical calculations show that the water splitting and hydrogen coupling reactions in alkaline HER occur on the surfaces of metals and oxides,respectively,and the charge transfer between the metal/oxide interface can further reduce the energy barrier during each stepwise reaction,thereby accelerating the whole HER process.