Study On Controllable Preparation And Electrocatalytic Performance Of Nickel-based Composites

Electrocatalytic water splitting reactions including hydrogen evolution reaction（HER）and oxygen evolution reaction（OER）are key reactions in the fields of fuel cells,electrolysis hydrogen production.At present,the most electrocatalytic performances are precious metal electrocatalysts such as Platinum,Rhodium oxide and Ruthenium oxide,but their high cost and limited reserves greatly limit their wide application.Therefore,the development of efficient,inexpensive and stable non-precious metal electrocatalysts is of great significance.Currently,improving the electrocatalytic activity and stability of non-precious metal electrocatalysts are key issues to be solved.In this paper we systematically studied the effects of element doping（cobalt,rare earth doping）and introduction of supports on the activity and stability of nickel-based catalysts by effectively regulating the surface interface structure of the electrocatalyst.The main results are as follows:（1）Cobalt doped composite electrocatalystsThe Ni₂P@NiPO composite electrocatalyst was successfully prepared by by hydrothermal method and phosphating.The experimental results showed that when the molar ratio of cobalt to nickel was 1:1,the precursor exhibited the best OER eletrocatalytic performance.In the oxygen evolution reaction（OER）process,when the current density was 10 mA cm^-2,the overpotential of CoNiPO precursor was 320 mV and Tafel slope was 84 mV dec^-1.In order to further improve its eletrocatalytic activity for phosphating,in the process of hydrogen evolution reaction（HER）,when the current density was 10 mA cm^-2,The overpotential of Ni₂P@CoNiPO was 180mV and the Tafel slope was 47mV dec^-1.And the improvement of the eletrocatalytic performance of the composite eletrocatalysts were attributed to the synergistic coupling between different cobalt-nickel atoms.（2）Carbon-based supported composite electrocatalystsDifferent carbon-based supported nickel phosphide composite electrocatalysts Ni₂P/NiPO@NGO（NGO Graphene）,Ni₂P/NiPO@GO（GO Graphene）,Ni₂P/NiPO@CNT（CNT Carbon Nanotubes）were prepared by hydrothermal method and phosphating.The experimental results showed that the introduction of carbon-based supports greatly improved the eletrocatalytic performance of the composites,mainly due to the good conductivity of the carbon-based materials,the large specific surface area and the electron transport in the eletrocatalytic process.It can be used as a support platform to enhance the electrochemical stability of the electrocatalyst in the electrocatalytic process.Compared with Ni₂P/NiPO@GO and Ni₂P/NiPO@CNT composite eletrocatalytic materials,Ni₂P/NiPO@NGO composite eletrocatalytic material exhibited the best HER eletrocatalytic performance.When the current density was 10 mA cm^-2,the overpotential of Ni₂P/NiPO@NGO composite eletrocatalytic material was the lowest（248 mV）,the Tafel slope was 42mV dec^-1.Compared with GO,CNT,the NGO improved the eletrocatalytic activity of composite eletrocatalytic materials mainly because NGO contains amino groups to provide a variety of immobilized active sites to improve the electrical contact between the redox active center and the electrode surface,and providing a channel for the continuous transfer of electrons to the electrodes,thereby facilitating energy dispersion and mitigating degradation of eletrocatalytic performance.