Research On The Design And Oxygen Evolution Properties Of Electrocatalysts Based On Boehmite

The development of electrocatalysts toward oxygen evolution reaction（OER）has been spread to many materials including oxides,metals,non-metals and even organics.And the general strategies to enhance the catalytic properties of OER electrocatalysts have been conducted considering many aspects from atomic level to the overall designing,but difficulties and shortcomings such as the correlations among the treatment of materials,the physicochemical properties and electrocatalytic properties still remain.Meanwhile,boehmite（γ-Al OOH）,which is one kind of traditional material studied for many years,obtains high thermal conductivity,high stability and is quite easy to be prepared,along with wonderful characteristics brought by the layered structure that surrounded by hydroxyl groups.And till now,boehmite has been applied as absorbants,support of organic catalysts and in medical fields.This project aims to enhance the electrocatalytic properties of boehmite based on two aspects:on one hand,focusing on the design and synthesis,study the physicochemical effects of doping by transition metals and compositing with layered double hydroxides（LDHs）,together with the changes of electrocatalytic OER performance;on the other hand,focusing on the functional treatment,study the physicochemical effects of samples treated by ball-milling,O₂ plasma and the introduction of transition metal（soak in solution）,together with the changes of electrocatalytic OER performance.First of all,pure and V or Ni-doped boehmite nanorods can be effectively prepared through a hydrothermal method.Pure boehmite particles obtain a uniform micrography of thin nanorod,while the intrinsic electrocatalytic properties toward OER is quite poor;the doping of V or Ni would not change either the micrography nor band gap of boehmite,but the dopant V would somehow induce distortion in the lattice of boehmite,which is harmful for the electrocatalytic reaction,but also results in smaller shape of particles and more active sites;the dopant Ni would introduce a new chemical bond,Ni-Al bond,which,would not change the host lattice and is beneficial to the electrocatalytic activity.Then,the ball-milling would cause the samples to lose some hydroxyls and maintain somekind of strain and vacancies,together with the micrography changed from thin nanorod to thin,round sheet and much enhanced electrocatalytic properties;the treatment with O₂ plasma would lead to the coexistence of hydroxyls,OH^-and the doped O,and when the coexistence reaches a balance state,the electrocatalytic performance becomes the best,along with the changing of strain on the surface of samples;the introduction of Co or Fe to the surface of samples would strongly enhance the electrocatalytic activity,but the Ni species do not perform the same;treated by the above-mentioned three methods in succession,the overpotential of sample has been reduced to only 400 m V with a Tafel slope reduced to 52 m V dec^-1 which is about 9.3%as low as that of the pure boehmite,demonstrating strongly enhanced electrocatalytic properties toward OER.At last,the in situ growth of Fe₁Ni₁ LDH or Fe₁Co₁ LDH onto pure,and V or Ni-doped boehmite nanorods could be easily realized through a simple method in solution,and the boehmite remains as single-crystalline,thin nanorod while the as-grown LDHs are amorphous,ultrathin nanosheets;the electrocatalytic activity of both Fe₁Ni₁ LDH and Fe₁Co₁ LDH are quite strong,but the long-term electrolysis would result in more and more inactive species,leading to poor electrocatalytic stability;however,the composites of Fe₁Ni₁ LDH or Fe₁Co₁ LDH with pure,and V or Ni-doped boehmite display little poor electrocatalytic activity,of which the optimal performance is that the overpotential is 271 m V with a Tafel slope of 27 m V dec^-1,together with strongly enhanced long-term（50 h）electrocatalytic stability,which benefits from the effective,boehmite-induced promotion of the transport of ions and intermediates.Through the above-mentioned methods toward the optimization of the electrocatalytic OER performance on boehmite,this project obtains excellent electrocatalysts considering in many aspects,and gains insights into the effects brought by the defects,micrography,strain,foreign atoms/cluster/compounds onto boehmite,together with relations to the electrocatalytic OER performance.