Integrating Hydrogen Production With Aqueous Selective Semi-Dehydrogenation Of Tetrahydroisoquinolines Over A Ni₂P Bifunctional Electrode

As an ideal clean and pollution-free energy carrier,as well as an important chemical raw material,hydrogen plays an important role in today’s world with severe problems such as energy shortage and environmental pollution.Electrocatalytic water splitting is one of the most potential ways to produce hydrogen.However,due to its sluggish kinetics of anodic oxygen evolution reaction（OER）,the energy conversion efficiency of overall water splitting is greatly limited,and the cost of hydrogen production is greatly increased.Therefore,exploring an alternative anodic reaction with accelerating kinetics to produce value-added chemicals with high selectivity,especially integrated with promoted hydrogen generation,is highly desirable.Nevertheless,the types and quantity of such alternative anodic reactions are still limited,and in most cases,the fully electrooxidized products are obtained.Thus,developing an alternative anodic reaction to drive controllable transformations of chemicals into corresponding semi-oxidized products with high selectivity and industrial practicability is highly challenging but more significant.In this thesis,a selective semi-dehydrogenation of tetrahydroisoquinolines（THIQs）instead of OER is proposed to boost the H₂ evolution reaction（HER）in water.Both value-added semi-dehydrogenation products and H₂,can be obtained at a much lower cell voltage than that of overall water splitting.The main research contents were summarized as follow:Using porous Ni₂P nanosheets as the model electrode,we demonstrate an efficient strategy to promote H₂ production by replacing OER with thermodynamically more favourable selective semi-dehydrogenation of THIQs over a Ni₂P bifunctional electrode.The value-added semi-dehydrogenation products,dihydroisoquinolines（DHIQs）,can be selectively obtained with high yields at the anode.The in situ potential-dependent Raman spectroscopy indicated that the controllable semi-dehydrogenation is attributed to the in situ formed Ni^II/Ni^III redox active species.Furthermore,such a strategy can deliver a variety of DHIQs bearing electron-withdrawing/donating groups in good yields and excellent selectivities,and can be applied to gram-scale synthesis.A two-electrode Ni₂P bifunctional electrolyzer can produce both H₂ and DHIQs with robust stability and high Faradaic efficiencies at a much lower cell voltage than that of overall water splitting.This work opens an economical and highly efficient route for the electrochemical production of both hydrogen and DHIQs.