Fabrication Of Co₉S₈/Ni₃S₂ Electrodes And Their OER Investigation

With the development of social economy and the increase of population,more and more traditional fossil energy are consumed,which leads to the increase of harmful gas emission and environmental pollution.Nowadays,every country is trying to develop new energy sources.Among them,hydrogen energy is a kind of new energy sources which has the advantages of cleanness,environmental protection and high calorific value.At present,the most promising way to produce hydrogen is electrochemical water splitting.The main catalysts for hydrogen production from electrochemical water splitting include platinum,ruthenium,iridium and their oxides,which are expensive and rare.Therefore,the most urgent task is to develop a cheap and excellent catalytic performance of the catalyst to replace precious metals,reducing the cost of industrial hydrogen production.In this thesis,according to the the recent study of metal sulfides and phosphide electrode materials for oxygen evolution from electrochemical water splitting,Co?OH?₂/NF nanosheets,Co₉S₈/Ni₃S₂ nanosheets and Ni₃S₂/Ni2P catalytic materials are prepared by hydrothermal method to catalyze oxygen evolution from electrochemical water splitting.The main contents of this thesis include:1.The Co?OH?₂ catalyst is grown on nickel foam substrate by one-pot hydrothermal method,and it has a small overpotential at 10 mA/cm2??=0.255 V vs RHE?.which is lower than optimal catalytic performance of commercial RuO2??=0.263 V vs RHE?.The 12 h V-t stability curve is tested in 1M KOH solution,which shows almost the same potential as the initial V-t curve,and shows good stability.The main reasons for speculating are as follows:?1?Co?OH?₂/NF has excellent catalytic performance for electrochemical oxygen evolution;?2?the splitting Co?OH?₂ nanosheets supported by three dimensional nickel foam have good electrical conductivity.which is conducive to electron diffusion;?3?the special structure of splitting Co?OH?₂/NF nanosheets improves the catalytic performance.2.The Co?OH?₂/NF catalyst prepared by the previous step is further vulcanized by hydrothermal method to prepare Co₉S₈/Ni₃S₂ catalyst.The preparation method of the catalytic material was simple and easy.Compared with the nickel foam and Co?OH?₂/NF,Co₉S₈/Ni₃S₂ has a lower initial potential;The overpotential of Co₉S₈/Ni₃S₂ catalyst is 0.226 V?vs RHE?at 10 mA/Cm2,which is smaller than the commercial RuO2??=0.263 V vs RHE?and Co?OH?₂/NF nanosheets??= 0.255V vs RHE?.The results show that the prepared Co₉S₈/Ni₃S₂ has better catalytic activity.The Tafel slope of the Co9Ss/Ni₃S₂ catalyst is 39 mV·dec-1,which is smaller than the Tafel slope of the Co?OH?₂/NF nanosheets?59 mV·dec-1?.The 20h I-t stability curve shows that the current density has no obvious change,which proves that it has good stability.Based on the above data,it shows that the oxygen evolution performance of Co?OH?₂/NF nanosheets can be greatly enhanced by sulfuration.3.Using hydrothennal method and high temperature calcination method,the Ni₃S₂/Ni2P catalytic material is synthesized.The cyclic voltammetry curves show that the Ni₃S₂/Ni2P catalyst has lower initial potential than that of N1₃S₂ catalyst.The overpotential at 10 mA/cm2 is 0.301 V vs RHE,which is significantly lower than that of Ni₃S₂ nanosheets??=0.367 V vs RHE?.The Tafel slope is 31.7 mV·dec-1 and also smaller than that of Ni₃S₂ nanosheets?88 mV·dec-1?.In addition,the 20 h I-t stability curve of Ni₃S₂/Ni2P catalyst at 20 mA/cm2 shows that the current density does not change obviously,which indicates that the Ni₃S₂/Ni2P catalyst has good stability.