Research On The Synthesis And Water Electrolysis Performance Of The Nanoarray Catalytic Electrode

With the growing human yearning for a better environment,the development of hydrogen fuel vehicles has been raised to a new height,which directly facilitates the development of its related industries of hydrogen fuel vehicles.Especially for hydrogen production industrial,China will build 1000 hydrogen stations by 2030 according to statistics.At that time,the demand of hydrogen fuel will be more urgent for human.Among the various hydrogen production method,the water electrolysis has attracted intensive attention due to its high purity of produced hydrogen and simple operation.By combining with wind,tidal,nuclear,solar and other clean energy,100%zero emission can be achieved,which can completely solve the energy and environment problem.So it can be concluded that the water electrolysis is bound to be the major method for the future hydrogen production industrial.The most important part of the water electrolyzer is the catalytic electrode.Using the effective electrode can obviously overcome the barrier of the cathode hydrogen evolution reaction(HER)and the anode oxygen evolution reaction(OER)to save the energy and cost of hydrogen production.Therefore,exploring superior activity,durability and affordable catalytic electrode is highly desirable for water electrolysis industry.In this paper,a series high activity catalytic electrode with core-shell composite hybrid nanoarray structure were designed and prepared based on the non noble-metal phosphide.Then various modern characterization methods were used to study the effects of the reaction conditions on the structure,morphology,element composition and valence state of the catalytic electrodes.While,their electrocatalytic properties(HER,OER)were also studied and analyzed systematically to clarify the catalytic mechanism of the efficient electrode with the composite hybrid nanoarray structure.On this basis,the high efficient catalytic electrode was assembled into the water electrolyzer which is applied into the traditional engine.Then a new type combustion mode of gasoline engine by blending hydrogen and oxygen was proposed.Moreover,the GT-Power software was used to simulate the working process of the engine under the combustion mode,and optimize the relevant parameters.The main research contents are summarized as follows:1)By hydrothermal and phosphorization process,the phosphide hierarchical nanoarray catalytic electrodes were prepared on flexible carbon cloth with high conductivity,which was directly used as the growth substrate as well as the current collector.Moreover,by changing the content of Fe doping,the morphology and structure of the catalytic electrode was transformed from the pure nanowire array to the nanowire-nanosheet hierarchical array,and finally to the pure nano sheet array.The change of the chemical composition and morphology could effectively regulate the performance of the catalytic electrode during the overall water electrolysis.Therefore,the electrochemical research results showed that the CoNi0.5Fe0.125P catalytic electrode with nanowire-nanosheet hierarchical structure had the best intrinsic activity and conductivity,as well as the abundant reactive sites,so it showed the excellent electrochemical catalytic activity.During the HER and OER,the CoNi0.5Fe0.125P catalytic electrode only required the overpotential of 74 mV and 290 mV to achieve the current density of 10 mA cm-2.2)On the basis of the phosphide catalytic electrode with nanoarray structure,the Ni2P nanoparticles were covered on the surface of Co0.5Fe0.5P nanowire to prepare a series of core-shell composite hybrid nanoarray catalytic electrodes(Ni2P@Co0.5Fe0.5P,CWNF)by the hydrothermal,calcination,electrodeposition and phosphorization process.The composite hybrid nanoarray structure could exert the synergistic catalytic effect between the core and shell catalysts.Moreover,by changing the time of electrodeposition,the ratio of the core and shell catalyst could be regulated to further optimize the synergistic catalytic effect,so as to improve the catalytic activity of the electrode during the overall water electrolysis.The results showed that the catalytic electrode prepared by electrodeposition for 20 min(CWNF-20)possessed the best activity for water electrolysis.It only required a small overpotential of 68 mV and 270 mV to afford the current density of 10 mA cm-2 during the HER and OER.Although this performance is still weaker than that of noble metal catalytic electrode,but obviously higher than that of the CoNi0.5Fe0.125P catalytic electrode mentioned above.3)In order to further exert the synergistic catalytic effect of the catalytic electrode with core-shell composite hybrid nanoarray structure,the chemical composition and crystal structure of core and shell catalyst were optimized.The high conductivity self-supported Mn doping Ni2P nanosheet with crystal structure was used as the core catalyst,which could accelerate the transformation of electrons from the collector to the shell catalyst;the amorphous NiOx nanofilms with large electrochemical surface area was used as the shell catalyst,which could improve infiltration property and provide abundant active sites for the reaction.Therefore,the catalytic electrode with core-shell composite hybrid nanoarray structure(A-NiOx/Mn5-Ni2P)possessed the excellent bifunctional catalytic activity for water electrolysis,and it only required the voltage of 1.54 V to achieve the current density of 10 mA cm-2,which had surpassed the combination of Pt/C‖IrO2/C noble metal catalytic electrode.4)The water electrolyzer for hydrogen production which was assembled by the excellent catalytic electrode with amorphous/crystal core-shell composite hybrid nanoarray structure,was applied into the traditional gasoline engine system.Then a new type combustion mode of gasoline engine by blending hydrogen and oxygen was designed and developed.Moreover,the GT-POWER software was used to simulate the work state of the engine under this combustion mode.The results showed that this combustion mode of gasoline blended hydrogen and oxygen endowed the engine the better fuel economy,power performance and emission characteristics compared with the pure gasoline and gasoline blended hydrogen combustion modes.