Preparation And Performance Of Graphdiyne-Based Single-Atom And Hybrid Catalysts

Noble metals(Pt,Pd,etc.)reveal their specific catalytic performance in a variety of catalytic fields,which show very important scientific research and applicable value.However,the high-cost of noble-metals limit their large-scale applications.One of the effective ways is to uniformly distribute noble-metal single-atom catalysts on the supports,which can dramatically reduce the usage of noble metals,as well as extremely improve the utilization rate,catalytic activity and selectivity.Another way is to replace the traditional noble-metal catalysts with non-noble-metal catalysts,which is also efficient to reduce the cost of catalyst.But the non-noble-metal catalysts are generally low activity.Hence,it is a huge challenge to design low-cost and effective catalysts with both excellent catalytic activity and stability.Graphdiyne(GDY),as a novel carbon allotrope,combines both sp-and sp²-hybridized carbon and has a two-dimensional(2D)layered and porous structure.Different from other carbon materials,GDY exhibits some special properties,such as abundant acetylenic bonds,largely exposed surface,and porous structure etc.Therefore,GDY can be utilized as an excellent support to prepare catalysts via stabling single metal atom or forming hybrid materials.One of the goals of this dissertation focuses on designing and optimizing single-atom catalysts by using GDY as the substrate to improve the catalytic activity and atomic utilization of noble metal catalysts.The other is aims at optimizing the catalytic performance of non-precious metal catalysts by coupling graphdiyne with non-precious metal catalysts.Therefore,the main research results are summarized as below:1.We put forward a simple method for the synthesis of two Pt SACs(Pt-GDY1 and Pt-GDY2)on the support of GDY.The coordination environments of Pt atoms in Pt-GDY1 and Pt-GDY2 were five coordinated Pt atoms of C₁-Pt-Cl₅ and four coordinated Pt atoms of C₂-Pt-Cl₂,respectively.Pt-GDY2 shows the highest HER catalytic performance,with a mass activity up to 3.3 and 26.9 times more active than Pt-GDY1 and commercial Pt/C catalysts,respectively.The outstanding HER catalytic activity of Pt-GDY2 originates from its near to zero Gibbs free energy,as well as its higher unoccupied density of states of Pt 5d orbital.2.Single-atom catalyst(Pd^s-GDY)and nanoparticle catalysts(Pd^NP1-GDY and Pd^NP2-GDY) were successfully prepared by using GDY as the substrate.Then,the structure and the alkyne hydrogenation performance of all catalysts were analyzed.Results show that,Pd^s-GDY possesses high catalytic activity,selectivity,and stability for semihydrogenation of phenylacetylene.What's more,the excellent semihydrogenation performance of Pd^s-GDY could also be further extended to many other alkyne substrates.While,Pd^NP1-GDY and Pd^NP2-GDY show poor semi-hydrogenation performance.3.2D/2D heterojunction of Ni-Co-P/GDY was prepared by electrochemical depositing Ni-Co-P on GDY as a bifunctional electrode for overall water splitting.Ni-Co-P/GDY shows remarkable electrocatalytic activity for both HER and OER in 1.0 M KOH solution.An overall water-splitting electrolyzer with this bifunctional electrocatalyst can afford 10 m A/cm² current density at a very small cell voltage of 1.60 V.GDY,as the electron-donating,can optimize the electronic structure of Ni-Co-P to improve the catalytic performance.