Regulation Of Surface Reconstruction Of Nickel-based Catalyst In Low Applied Potential And Its Oxygen Evolution Reaction Performance

The exploitation of highly activity and low cost oxygen evolution reaction（OER）catalysts is the key to the development of water splitting technology.Transition metal-based catalysts are inexpensive and tended to undergo surface reconstruction during the electrochemical process,which can form abundant reactive sites and thus promote the adsorption and desorption of intermediates.True active surfaces are generated in situ during the OER process,and reasonable regulation of the reconstruction process is of great significance to enhance the catalyst performance.However,the reconstruction process in the high potential region proceeds simultaneously with OER,leading to a more complex reaction with fast reaction rate and difficult regulation.In contrast,the reconstruction process in the low-potential region avoids the complex reactions caused by the simultaneous proceeding with OER and can be regulated by introducing external factors.Based on this,this thesis aims to investigate the reconstruction process of OER catalysts and to regulate the reconstruction process of nickel-based catalysts through a controlled discharge process in the low potential region.The surface reconstruction processes of heteroatom-doped nickel oxide,nickel phosphide with different crystalline degrees and different nickel-based compounds were investigated in detail.The details of the investigations are as follows:（1）P-doped nickel oxide（P-NiO）and nickel oxide（NiO）were used as catalysts to investigate the surface reconstruction process induced by the discharge phenomenon in the low potential region.It was found that the doping of P atoms endowed NiO with a more flexible surface structure,which led to the formation of abundant oxygen vacancies（V_o）and phosphorus vacancies（V_p）and generated more reactive sites after surface reconstruction in the low potential region.In addition,the surface reconstruction process accelerated the charge transfer rate and mass transfer process of P-NiO catalyst.Finally,the surface reconstruction process in the low potential region enhanced the current density（1.4 V vs Hg/HgO）of P-NiO by 33.7%.（2）Amorphous Ni₂P（A-Ni₂P）,low crystallinity Ni₂P（LC-Ni₂P）and high crystallinity Ni₂P（HC-Ni₂P）were used as catalysts to investigate the surface reconstruction process induced by scanning in the low potential region for Ni₂P with different crystallinity degrees.It was found that A-Ni₂P,LC-Ni₂P and HC-Ni₂P performed different discharge behaviors in the low potential region.LC-Ni₂P had relatively weaker surface stability and faster discharge rate,which led to the formation of more oxygen vacancies（V_o）during the reconstitution in the low potential region.Benefiting from the in situ formation of oxygen vacancies,the current density（1.4 V vs Hg/HgO）of the LC-Ni₂P catalyst was enhanced by 36.7%.（3）The surface reconstructions of different nickel-based compounds Ni₅P₄,Ni S₂and Ni Se₂ in the low potential region were investigated by controlled discharge processes.Compared with Ni S₂ and Ni Se₂,the surface reconstruction process in the low-potential region significantly accelerated the charge transfer rate of Ni₅P₄ while promoting the mass transfer process in the OER reaction.Notably,the current density（1.4 V vs Hg/HgO）of Ni₅P₄ was significantly enhanced by 68.8%after the surface reconstruction process in the low-potential region.