Synthesis Of Cucurbit[n]uril-based Supramolecular Assembly And Its Application In Electrocatalysis

Electrocatalytic carbon dioxide reduction using renewable energy provides an attractive way to produce storable carbon-neutral fuels.In order for this technology to be commercially applied,it is necessary to develop a catalyst with a multi-electron/proton transfer reaction with minimal energy loss,high rate and outstanding selectivity.In addition,with the increase in global energy demand,there is an urgent need to develop potential alternative fossil fuels and environmentally friendly new energy sources.As a sustainable clean energy,hydrogen is considered a potential substitute for fossil fuels.Hydrogen evolution reaction（HER）is the cathode reaction in water electrolysis,which has been recognized as an efficient and green method for preparing hydrogen Therefore,the preparation of highly efficient and stable CO₂RR and HER catalysts has been a key research issue in recent years.Our work is also focused on these two aspects.The content is as follows:（1）Through liquid phase diffusion method,Cucurbit[8]urils（CB[8]）and H₂Pt Cl₆forming supramolecular self-assembly materials,which can be used as low-Pt catalysts by simple electro-reduction.Utilizing the abundant hydrogen bonds existing in the highly ordered molecular structure of supramolecular assembly materials can well limit the rapid agglomeration of metal particles,thereby greatly improving the atomic utilization of Pt.The obtained CB[8]-Pt not only has a mass activity 23 times higher than that of 20%Pt/C,but also has good electrochemical HER stability.This work provides new guidance for the rational design of high-activity and stable low-platinum catalysts.（2）First,employing supramolecular self-assemblies as precursors,three well-defined types of Au NPs protected by rigid macrocyclic CB[n]were successfully obtained using a moderate ultrasonic reduction method.The evenly distributed Au NPs with an average diameter of around 4 nm showed exposed high-density uncoordinated surface atoms,facilitating the sorption of substrates and mediates during catalysis.The CB[n]-Au catalysts show excellent catalytic activity and selectivity toward CO₂ electroreduction to CO,which can be ascribed to the unique structural features and the intrinsic ability of CB[n]to interact with small gaseous particles.Furthermore,the best durability for CO₂RR was presented by the Au NPs protected by CB[6],where the FE_CO and jtot values were maintained without any obvious decline up to 72 h during chronoamperometry tests.The effects of the volume,the cavity size and the solubility of the different CB[n]s on the electrocatalytic performance of the Au NPs have been revealed for the first time.This work also provides a strategy for the development of CB[n]-based catalysts for different electrochemical reactions.（3）Self-assembly of Me₁₀CB[5],Pd Cl₂ and MCl₂（M=Ca,Sr,Cd）at room temperature to construct three supramolecular coordination polymers,and high temperature reduction in a hydrogen atmosphere to obtain palladium nanoparticle catalyst load on the rich alkaline earth metal/transition metal substrate Utilizing the abundant electrostatic interaction in the supramolecular precursor and the unique confinement effect of the melon ring,it effectively inhibits the agglomeration of metal particles.Among them,palladium nanoparticles loaded on a substrate rich in alkaline earth metals have better activity and selectivity for the conversion of CO₂ to C₁.This is related to the better enrichment capacity of alkaline earth metals for carbon dioxide to promote the electrocatalytic carbon dioxide reduction reaction,and we also proved our point of view through carbon dioxide adsorption.This work proposes for the first time that the introduction of alkaline earth metals in the catalyst can improve the enrichment of small reaction molecules on the electrode surface to enhance the activity and selectivity of the electrocatalytic carbon dioxide reduction reaction.It also provides a new idea for the development of catalysts for different reactions.