Preparation Of Molybdenum-based Composite Nanostructures And Their Performance For Electrocatalytic Water Splitting

Fossil fuels can take part major role for continuous development of human society.In the future social development in the world will be faced a critical crisis because due to the rapid utilization of traditional energy sources?coal,oil,and natural gas?.In addition,massive combustion of fossil fuels can create a serious environmental problem.To achieve sustainable energy production,there is an urgent need to develop advanced energy conversion technologies to reduce the burden of energy demand.Among them,wind energy,solar energy,and water energy have the ability to be converted into other available energy in practical applications,such as hydrogen energy.Hydrogen is promising energy sources have several advantages such as high energy density,clean energy,and environmental protection.However,unlike primary energy sources such as coal,oil,and natural gas,hydrogen cannot naturally exist in large quantities in nature.The development of large-scale and inexpensive hydrogen production technology is the primary problem facing hydrogen energy strategy.At present,there are more than 500 billion cubic meters of hydrogen produced in the world each year.The main sources are the high-temperature cracking natural gas method and the water gas method.Only about 4% of the hydrogen is produced by electrolyzing water.Although the first two hydrogen production processes are relatively simple,it is still difficult to get rid of the use of fossil fuels due to the large amount of greenhouse gas CO2 produced,and it cannot solve the environmental and energy problems from the root causes.Taking into account the efficiency and convenience of storage,electrochemical water splitting has proved to be one of the most promising strategies due to its advantages of simplicity,high efficiency,easy production,and environmental protection.At present,the Pt or Pd and Ir O2 or Ru O2 earth-abundant catalysts have been used for HER and OER reactions respectively to boosting reaction kinetics.However,these materials have limited for wide-scale application due to high cost,and less abundance.Thus developing an alternative robust catalyst for overall water splitting?OWS?reactions have becomes challenging in electrocatalysis research.Based on the above assumptions,the research content of this paper is as follows:1.The disordered Ni,Fe-co-doped MoS₂ nanosheets are synthesized by using combined the simple alkaline fusion method with the hydrothermal method.The designed catalyst has a large specific surface area,which can provide more active sites during electrochemical reactions.As results,disordered Ni,Fe-co-doped MoS₂ nanosheets show excellent HER and OER activities in alkaline media to needs the 120 m V and 280 m V overpotential to achieve current densities of 10 m A/cm2 and 20 m A/cm2,respectively.Moreover,the cell assembled by Ni,Fe-co-doped MoS₂ as both cathode and anode required cell voltage of 1.57 V to achieve a current density of 10 m A cm^-2.2.The layered MoO_x@NiS₂ hybrid nanostructure are successfully prepared by simple hydrothermal reaction and controllable vapour deposition method.As results,The layered MoO_x@NiS₂ hybrid nanostructure show excellent HER and OER activities in alkaline media.For HER and OER,required 101 m V and 278 m V overpotential to reach a current density of 10 m A cm^-2 and 20 m A cm^-2,respectively.The MoO_x@NiS₂ heterogeneous composite structure showed excellent catalytic stability under under 24 h constant voltage operation.The electrochemical cell assembled with MoO_x@NiS₂ as the cathode and anode need a potential of 1.62 V at 10 m A cm^-2.In the case of overall water splitting reaction tested for 15 h at a voltage of 1.65 V shows minute changes in current density.3.The Ni-Fe-Prussian blue nano-cube was synthesized by precipitation method,and consequently a hollow Ni-Fe-Prussian blue nano-box was obtained by hydrothermal reaction in an aqueous ethanol solution of TAA.The nano-box was used as a template through hydrothermal method and vapor deposition method,and MoS₂/NiS₂ nanosheets were grown on the outside of the?Fe,Ni?S₂ nanobox.The?Fe,Ni?S₂@MoS₂/NiS₂ electrocatalysts exhibited excellent hydrogen and oxygen evolution performance in alkaline environment.The phase interface of?Fe,Ni?S₂@MoS₂/NiS₂ not only provides abundant electroactive sites,but also promotes the transfer of electrons and ions in electrode/electrolyte interface.The special hollow structure reduce the charge transfer pathway as well as increases the contact area,and expose more active sites.The exhibited low cell voltage of 1.58 V at current density 10 m A cm^-2.