Study Of The Effect Of Phosphorus Oxoanion-intercalated In Ni-Fe LDH As Oxygen Evolution Catalysts

Since the dried up of fossil energy,finding a environment friendly and replaceable energy has become an urgent affair.Hydrogen has got a high energy density,it is a great candidate for the fuel of heat engine and the raw material of fuel cell.The only product after the reaction is water,the product can be split back to hydrogen and achieve zero release.The simplest way to make the make the cycle work is to split water by electric.The electrolysis water splitting reaction include two half reactions:hydrogen evolution and oxygen evolution.The oxygen evolution is a four electron transfer process which is relatively complicated and dynamic unfavorable,so an appropriate catalyst is necessary here to enhance the process.The oxygen evolution reaction took place on a relatively high over potential,the small oxygen bubble generated from the electrode surface through the reaction will impact and corrode the electrode without a break,all these disadvantages ask for a high standard of the oxygen evolution electrode.The common material of oxygen evolution reaction electrode include noble metals,oxide or compound of base metals,non-metal materials,etc.In recent years,the layered double hydroxides(LDHs)has drawn more and more attention to act as oxygen evolution catalyst because of it's outstanding catalysis performance,low cost and simple synthesis methods.In this work,different phosphorus oxoanion intercalated Ni-Fe layered double hydroxides were synthesized and the regularity of these oxygen evolution catalysts were studied as below:Different phosphorus oxoanion intercalated Ni-Fe layered double hydroxides were prepared through constant pH co-precipitation process,the category and the concentration of the anion intercalated between the laminate can be adjusted by the anion in the reactant,the product has got an excellent nanosheet structure.This method provide a new approach to substitute the anion between laminate in the Ni-Fe LDHs.The oxygen evolution reaction performance of different phosphorus oxoanion or carbonate intercalated Ni-Fe layered double hydroxides were studied.An excellent catalyst with stable electrochemical behavior and a low onset potential of 215mV,a small Tafel slope of 37.7mV/dec was prepared.Though XPS and other analysis measurement,we find that the valence state of the cations on the laminate can be effected by the valence state of the anions intercalated between the laminates.And the oxygen evolution reaction performance of the Ni-Fe LDH is decided by the valence state of the cations on the laminate.This concept that influence the valence state of the cations on the laminate by the anions intercalated between the laminate should be inspiring for the further promotion of the LDH-based oxygen evolution electro-catalyst performance.