Study On The Synthesis Of Nickel-iron-based Electrocatalyst And The Performance Of Electrolyzed Water

Recently,enough efforts have been made to strengthen the electrocatalytic activity of nickel-iron hydrotalcite nanosheets,such as to produce a single-layer structure,produce arrays on nickel foam or nickel mesh,intercalation of anions,sulfide,noble metal single atom loading,third metal doping,etc.At the same time,in order to explore novel and multifunctional water electrolysis catalysts,high-entropy alloy(HEA)is expected to provide a broad platform for the development of water-resolving catalysts due to its complex structure and functional characteristics.The research content and conclusions of this thesis on Ni-Fe metal water electrolysis catalysts can be divided into the following points:(1)Improve the OER performance of NiFe LDHs through V metal doping.NiFe LDHs catalysts with different Ⅴ doping levels were synthesized on nickel mesh and nickel foam.It was found that the OER performance of Ni2FeV0.3 was the most excellent on either the nickel foam carrier or the nickel mesh carrier.At a current density of 10 mA/cm2,the overpotential of NF/Ni2FeV0.3 is 185 mV,and the overpotential of the nickel mesh/Ni2FeV0.3 is 198 mV,which are both lower than the 220 mV of Ni2Fe LDHs without V doping.It shows that the proper amount of V doping can greatly improve the OER performance of NiFe LDHs.Nickel mesh/Ni2FeV0.3 also has excellent OER activity in simulated alkaline seawater,its overpotential is only 204 mV at a current density of 10 mA/cm2.The performance of the NF/Ni2FeV0.3 catalyst was further improved after high-temperature alkaline washing,and the overpotential required to achieve a current density of 10 mA/cm2 is 180 mV.Besides,the Ni2FeV0.3 tested by multiple cycles of CV have continuous stability.The growth of NiFe LDHs on sulfided nickel foam also improves the OER activity.Under an overpotential of 190 mV,a current density of 10 mA/cm2 can be reached,but the stability of the catalyst is poor.(2)Ni2FeV0.3 was supported on two specifications of nickel mesh and NF as the anode catalyst,and a kind of NiMO alloy was used as the cathode catalyst.The NiMO alloy catalyst was also supported on these three types of supports.NF/Ni2FeV0.3 acted as the anode catalyst,and NF/NiMo acted as the cathode catalyst,which had the best performance.An additional voltage of 1.5 V can be applied to achieve a current density of 10 mA/cm2,and in the long-term stability test of twenty hours,the change in current density is minimal.So the stability of the overall water splitting was extremely excellent.And the performance test of the catalyst was also carried out under high current density.Ni2FeV0.3 can achieve a current density of 1000 mA/cm2 under an overpotential of 304 mV.When used as an anode catalyst,a voltage of 3.23 V needed to be applied to reach a current density of 500 mA/cm2 during the test of overall water splitting.(3)The Al2FeCoNi2Ce catalyst was first calcined with high temperature H2 and then washed with high temperature alkali.It concluded that Al2FeCoNi2Ce-H2-NaOH was the most excellent catalyst for overall water splitting.In HER and OER,128 mV and 230 mV were required to achieve a current density of 10 mA/cm2,respectively.When Al2FeCoNi2Ce-H2-NaOH acted as a cathode and anode catalyst at the same time,to achieve a current density of 10 mA/cm2,the additional applied voltage is 1.59 V in the process of overall water splitting.The stability tests of OER,HER and overall water splitting have also proved that the stability of Al2FeCoNi2Ce-H2-NaOH was outstanding.Al2FeCoNi2V-H2-NaOH has the best catalytic activity in the OER process with only 220 mV overpotential needed to achieve a current density of 10 mA/cm2,but its HER performance was poor.(4)Al2FeCoNi2M(Cu,Mo,Mn)was first calcined in high temperature H2 and then subjected to high temperature alkaline washing treatment,the catalytic performance has been greatly strengthened.In the process of HER,in order to achieve a current density of 10 mA/cm2,the overpotentials of Al2FeCoNi2Cu-H2-NaOH,Al2FeCoNi2Mo-H2-NaOH and Al2FeCoNi2Mn-H2-NaOH were 138 mV,150 mV and 150 mV.