Fabrication And Performance Investigation Of Nickel-based Electrode For The Coupling Of Electrolysis For Hydrogen Production And Oxidation Of Tetrahydroisoquinoline

Many new green and clean energy sources,such as tidal energy,solar energy and nuclear energy,have received increasing attention.Hydrogen is regarded as an ideal energy carrier due to its clean and pollution-free environment and plays a key role in solving the energy shortage and environmental pollution problems faced by the world.Among them,hydrogen is regarded as an ideal energy carrier due to its clean and pollution-free environment,which plays a key role in solving the current problems of energy shortage and environmental pollution in the world.At present,electrocatalytic water cracking is one of the most promising ways to obtain H₂ sustainably.However,due to the high energy barrier of the anodic oxygen evolution half-reaction（OER）involving the four-electron transfer process,and most of the catalysts currently in circulation are precious metals,the conversion efficiency of total hydrolytic energy is low and the cost of hydrogen production is high.Therefore,it is of great significance to explore and develop suitable anodic electrochemical reaction to replace oxygen evolution half-reaction in order to produce high value-added chemical products while improving energy conversion efficiency of hydrogen production from water decomposition.The number and types of existing anodic substitution reactions are limited,and the resulting products are usually completely oxidized products,so it is very challenging and significant to research and develop an anodic substitution reaction which can realize the controllable conversion of chemical substances into semi-oxidized products with high industrial practicability.Oxidized tetrahydroisoquinoline（THIQ）,as an anode replacement reaction,can effectively reduce the required potential of the reaction.The oxidized products of dihydroisoquinoline and isoquinoline have higher economic value than O₂,thus improving the economic benefit of the whole reaction system.Nickel-based nanomaterials in 3d transition metals（3D-TM）have the advantages of high activity,abundant reserves and low price.Nickel-based nanomaterials,if properly activated,can achieve comparable or even better performance than noble metal catalysts.Therefore,Nickel-based nanomaterials are regarded as promising non-noble metal catalytic materials.Therefore,the objective of this study is to develop a catalytic electrode with high semi-dehydrogenation selectivity for THIQ by coupling electrolytic water hydrogen production with THIQ oxidative dehydrogenation.Taking nickel-based materials as the research object,a nickel-based nano-catalytic electrode with different morphology and excellent catalytic performance was constructed,and the influence of the introduction of each component on the electrocatalytic performance of nickel-based materials was investigated.The specific research content is summarized as follows:（1）Using Ni Co₂O₄ as precursor and nickel foam as substrate,the three dimensional NiCoP/NF samples were prepared by simple hydrothermal method and high temperature phosphating strategy.In the catalytic THIQ oxidation test,NiCoP was observed to have better performance than Ni₂P and Co P,indicating that the synergistic effect between bimetallic ions is conducive to improving the catalyst performance.Under the test conditions,the prepared electrode can successfully catalyze the oxidation of THIQ.The oxidation products include dihydroisoquinoline and isoquinoline,and the yield of dihydroisoquinoline is 65%.The yield of dihydroisoquinoline generated by the catalytic electrode remained 60%after six cycles.A dual-function electrolytic cell assembled by two NiCoP/NF electrodes（used for oxidative dehydrogenation of HER and THIQ,respectively）was tested i-t at 2.0V.A large amount of hydrogen was generated at the cathode side to generate dihydroisoquinoline and isoquinoline at the anode side,and the yield of dihydroisoquinoline was 65%.The yield of dihydroisoquinoline produced by electrolytic system remained unchanged after six cycles.（2）Ag-Ni O composite material was obtained by growing nano-flower-like Ni O on nickel foam skeleton by hydrothermal and calcined method.It was observed that Ag-Ni O had better performance than Ni O in catalytic THIQ oxidation tests.It is speculated that the nickel site is the active center of the composite material,and the silver species can improve the conductivity of the material and regulate the electronic structure of the active center.In 1.0 M KOH solution,the catalytic electrode can successfully catalyze the oxidation of THIQ,and the yield of dihydroisoquinoline is 70%.The performance of the catalytic electrode did not decrease significantly after six cycles of utilization.Two Ag-Ni O/NF electrodes for dehydrogenation of HER and THIQ were used to construct a dual-function electrolytic cell.In the i-t test at 2.0V,the yield of dihydroisoquinoline formation on the anode side was 70%.The electrolytic system showed high stability,and the catalytic performance did not change significantly after six cycles.（3）Ni（OH）₂ nanosheets were grown on nickel foam substrate by hydrothermal method,Ni（OH）₂ was reduced to Ni elemental by reduction method,and porous Ni₃N/NF catalytic electrode was prepared by in-situ nitridation.It was observed in catalytic THIQ oxidation test that Ni₃N has good catalytic performance due to its porous and spongy structure and the synergistic effect between its components.In 1.0 M KOH solution,0.5 mmol THIQ was completely converted to dihydroisoquinoline and isoquinoline within 1 h,and the yield of dihydroisoquinoline was 76%.The electrode showed excellent stability.The coupling hydrogen evolution and THIQ semi-dehydrogenation system was constructed based on the prepared Ni3N/NF electrode,and the current density reached 10 m A cm^-2 at the potential of 1.413 V,which was smaller than that of the fully decomposed water（1.829 V）.The catalytic THIQ oxidation of Ni₃N/NF electrode was investigated by in situ Raman spectroscopy.It was found that the formation of Ni OOH on the surface of Ni₃N promoted the semi-dehydrogenation of THIQ during the catalytic reaction.