Preparation And Electrocatalytic Performance Of Supported Nickel-based Catalysts

The rapid development of current world economy mainly depends on the large-scale application of fossil fuels and their converted energy.However,the reverses of fossil fuels in earth are limited and their combustion products are strongly polluting,which leads to the increasingly serious energy crisis and environmental problems.Therefore,it is imperative to vigorously develop circulating clean energy to replace traditional fossil fuels.Hydrogen energy,as a clean energy with no carbon and high energy density,has aroused widespread public concern.To date,producing hydrogen by water electrolysis is considered to be the most effective hydrogen production method.Noble mentals,such as Pt et al.,are recognized as the most effective HER catalysts.However,the expensive cost and scarce reserves of noble metal catalysts greatly restrict their practical production and application.Therefore,it is of great significance to research and develop highly active non-noble metal electrocatalysts.In this thesis,two new ideas for the prepartion of nickel-based alloy catalysts was proposed,meanwhile,the composition,structure and electrical properties of Ni-Fe-P/NF,Ni-Co-Fe-P/NF,and Ni-Fe-P-Ni₃S₂/NF catalysts were systematically studied.The main results include following three aspects:（1）Ni-Fe-P/NF catalysts were prepared by facile electroless deposition and fast dealloying.The effects of preparation conditions on the composition,structure and electrolytic water performance of Ni-Fe-P/NF catalysts under alkaline conditions were studied.The results show that the Ni-Fe-P/NF catalysts electroless deposited for 60 min in electroless bath with 3:7 NiSO₄/Fe（NH₄）₂SO₄·6H₂O concentration ratios and then were immersed in 1.5 M HCl for 30 min exhibit superior electrocatalytic water-splitting activity,which has low HER and OER overpotentials of 72 and 228 m V in the current density of 10 m A cm^-2.It is found that the dealloying treatment could make the Ni-Fe-P/NF catalyst exposed a large number of defects,formed more active sites,increased the contact area between the electrolyte and the catalyst,and constructed an electron transport path,which resulted in Ni-Fe-P/NF catalyst exhibit excellent electrocatalytic water-resolving properties.（2）The Ni-Co-Fe-P/NF multi-alloy catalysts were loaded on the nickel foam substrate by electroless plating and dealloying.The effects of synthesis conditions on the composition structure and hydrogen evolution performance of Ni-Co-Fe-P/NF alloy catalysts under alkaline and neutral conditions were studied.It is proved that Ni-Co-Fe-P/NF catalysts exhibit optimal HER performance,when the electroless deposition time is 60 min,the dealloying time is 75 s,the HCl solution concentration is 3 M,and the concentration of NiSO₄,CoSO₄,and Fe（NH₄）₂SO₄·6H₂O is 5 g L^-1、15 g L^-1、5 g L^-1 in electroless bath,respectively.The Ni-CO-Fe-P/NF multi-alloy catalysts only require the HER overpotentials of 56 m V and 105 m V to reach the current density of 10 m A cm^-2 in 1 M KOH and 1 M PBS,respectively,which display that the Ni-CO-Fe-P/NF own great HER performance in the wide p H conditions.（3）Ni-Fe-P-Ni₃S₂/NF catalysts were synthesized by electroless composite plating.It is investigated that the effects of Ni S addition and electroless composite plating time on the composition,structure of Ni-Fe-P-Ni₃S₂/NF catalysts and the catalytic performance under alkaline conditions.The co-deposition of Ni S and Ni-Fe-P alloy can significantly increase the ECSA of the electrochemical activity of the catalyst,expose more active sites,optimize the electron migration rate,and reduce the catalyst resistance value,resulting in Ni-Fe-P-Ni₃S₂/NF exhibiting superior electrocatalytic performance under alkaline conditions.Ni-Fe-P-Ni₃S₂/NF catalysts require only 65 m V and 219 m V overpotentials to reach a current density of 10 m A cm^-2 in the hydrogen evolution and oxygen evolution reactions under alkaline conditions,respectively.Meanwhile,the potential of the Ni-Fe-P-Ni₃S₂/NF composite catalysts both as anode and cathode at a current density of 10 m A cm^-2are 1.5 V.All in all,the synthesized low cost Ni-Fe-P/NF,Ni-Fe-Co-P/NF,and Ni-Fe-P-Ni₃S₂/NF electrocatalysts exhibits excellent electrocatalytic activity and stability in the water electrolysis.These two-step sysnthesis strategies provides new insights into the design and fbracation of porous alloy catalysts and alloys/sulfides heterogeneous catalysts with superior electrocatalytic performance.