| With the increasingly prominent energy crisis and environmental problems,the exploration of new efficient energy conversion technology has become the focus of people's attention.Electrocatalytic reaction is one of the most promising sustainable energy conversion technologies,and the reaction rate is determined by the activity of the electrocatalyst.At present,the prevailing commercial catalysts for electrocatalytic reactions are precious metals with excellent electrocatalytic activity.However,they are faced with the problems of scarce abundance,high cost and poor stability.Exploring high-efficient,low-cost,and stable electrocatalyst is the primary task to accelerate the development of electrocatalytic reactions.Obviously,the electronic structure of the electrocatalyst plays a vital role in governing its activity.It is a feasible way to improve the catalytic activity of electrocatalyst by reasonably designing catalyst materials,changing its surface electronic structure,and then optimizing the adsorption energy of reactants,intermediates and products.To improve the electrocatalytic performances of transition metal matrix composites and reveal the intrinsic relationship among the microstructure,electronic behavior,and activity,this paper modulated the electronic structure of the catalysts(such as Mo S2,CoO,Co2P and single atomic catalyst)from the view of interface and defect regulations.The relationship among the microstructure,electronic structure and activity were also explored.The main contents are as follows:1.Co9S8-Mo S2 in-plane heterojunctions supported on N and S doped three-dimensional carbon(Co9S8-Mo S2@3DNSC)were prepared by the two-dimensional spatial confinement of NaCl template.The influence mechanisms of the interface on the hydrogen evolution reaction(HER)performance of Co9S8-Mo S2@3DNSC were investigated.It revealed that the sample of which the ratio of Mo S2:Co9S8 is 1:1 shows the highest HER activity,with low overpotential of177 m V at 10 m A cm-2 and tafel slope of 83.6 m V dec-1 for the HER in 1.0 M KOH.The density functional theory(DFT)calculation shows that the construction of Mo S2-Co9S8 in-plane heterojunctions promotes the OH-chemisorption at Co site and H chemisorption at S site,and then accelerate the cleavage of the HO–H bond and the combination of H*.At the same time,it also promotes the rapid charge transfer in the catalyst,which is beneficial for HER.2.“Zero dimension-two dimension”Co-CoO heterojunctions on the N doped graphene(CoO/Co@NG)were prepared by the method of recrystallized NaCl confinement.The synthesis mechanism and electrocatalytic performance of CoO/Co@NG as oxygen electrocatalyst were explored.It reveals that the precursor is sealed in the recrystallized NaCl,which ensure that the CoO obtained by calcining Co(OH)2 at high temperature remains the lamellar morphology.Meanwhile,the thermal expansioned NaCl will press the internal CoO and Co during the calcination process,which promotes the formation of Co-CoO interface with strong bonding force.The“Zero dimension-two dimension”Co-CoO heterojunctions not only promote the charge transfer between Co and CoO,but also modulate the charge distribution in the plane of CoO nanosheets,which promote the transportation of ions and electrons on the surface and modulate the adsorption strength of the intermediates on the active sites.Thus,CoO/Co@NG exhibits excellent oxygen reduction reaction(ORR)activity with onset potential of 0.94 V,half-wave potential of 0.83 V and excellent stability.3.The electronic structure of Co2P was modulated by Cu doping and the Cu doped Co2P nanoparticles were anchored on 2D ultrathin N,P-codoped graphene(Cu-Co2P@2D-NPG).The relationship among the microstructure,electronic structure and ORR performance was investigated by experiments and DFT calculations.It revealed that Cu doping can modulate the charge distribution and density of state,which weaken the binding strength of the adsorbed intermediates on the surface active sites,and then reduce the reaction barrier of the rate-determining step.As expected,the optimized Cu-Co2P@2D-NPG with 7.1%Cu doping exhibits the best ORR performance with the onset potential of 0.960 V and half-wave potential of 0.835 V.Meanwhile,Zn–air batteries assembled by the 7.1%Cu-Co2P@2D-NPC deliver excellent performance,with high power density of 236.1 m W cm-2,and exhibit high capacity of 736.8 m Ah g-1 and stability(160 h at 10 m A cm-2).4.Metal single atoms dispersed on three-dimensional N doped carbon materials(M-SAC@3DNC)were prepared by aerosol spray drying-pyrolysis method.The influences of different templates,metal types and loading mass on the microstructure and ORR performance of M-SAC@3DNC were investigated.It revealed that this strategy realized the large scale production of single atomic catalyst in industry with good universality and generality,and the metal loadings are more than 0.9 wt%.Among the M-SAC@3DNC,Fe-SAC@3DNC exhibits the highest ORR performance with the half-wave potential of 0.855 V and the limited diffusion current density of5.8 m A cm-2 which is better than Pt/C. |
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