Preparation And Electrocatalytic Properties Of Platinum Nanocatalysts Derived From Phosphine-Based Porous Aromatic Frameworks

With the surge in energy demand and increasingly serious environmental problems,hy-drogen（H₂）as a new clean energy has attracted widespread attention from researchers.At pre-sent,hydrogen evolution reaction（HER）technology is an effective way to prepare hydrogen,and commercial platinum（Pt）is the most widely used catalyst in HER.However,platinum nanoparticles（Pt NPs）cannot exist independently and stably in the solution,and are easy to leach or agglomerate into larger particles,thus affecting their catalytic effect.Therefore,the design and synthesis of stable Pt NPs support materials has important research significance and value.Porous aromatic frameworks（PAFs）with low-density,high specific surface area,good stability and flexible modification are important members of the porous material family.PAFs are widely used in catalysis,gas adsorption separation,energy storage and other fields.Phos-phine-based PAFs have rich P element in their skeletons,which has a unique electron-giving effect and can form a good coordination with metals,therefore,phosphine-based PAFs can be used as excellent Pt NPs support materials.In this paper,a series of phosphine-based PAFs were selected and a new phosphine-based PAF was designed and synthesized,and a series of efficient HER catalysts were prepared by post-synthesis and in-situ preparation strategies.The specific research work is as follows:1.A series of phosphine-based PAFs materials,PAF-93,PAF-94,PAF-95 and PAF-96,were selected to explore the effects of different phosphine-based PAFs on the loading capacity and catalytic activity of Pt NPs from the perspectives of skeleton composition and pore proper-ties of the support materials.Using the strong interaction between P and Pt in the phosphine PAFs framework,a series of supported Pt NPs catalysts were prepared by post-synthesis strategy:Pt@PAF-93,Pt@PAF-94,Pt@PA-95 and Pt@PAF-96.Among them,PAF-96 has a high spe-cific surface area compared to other phosphine-based PAFs.At the same time,the P-center and the N-giving electron in the pyridine unit in the PAF-96 framework have synergistic interaction with Pt NPs,which enhances the interaction force between the support material and Pt NPs,so the content of Pt NPs in the Pt@PAF-96 is the highest and the smallest size.Pt@PAF-96 has the best HER performance and high stability in cyclic testing.2.Using the adequate anchor points P and N in bis（2-pyridyl）phenylphosphine（Ph Py₂P）monomer,a new phospho-based PAF:PAF-99 was designed and synthesized by mild Friedel-Crafts alkylation reaction withα,α’-dibromo-paraxylene（DBp X）as a crosslinker.Two sup-ported Pt NPs catalysts（Pt-PAF-99 and Pt@PAF-99）were prepared using two strategies,in-situ preparation and post-synthesis,respectively.The results show that the size of Pt NPs in Pt-PAF-99 prepared in-situ is smaller,and it has a lower overpotential at a current density of 10 m A cm^-2 in HER test,and has ultra-high stability,and the HER catalytic activity is better.In this paper,phosphine-based PAFs are used as support materials for loaded Pt NPs,which not only gives full play to the advantages of high specific surface area,rich pore structure and excellent stability of PAFs,but also makes use of the strong coordination ability of P and Pt in the skeleton to achieve the effect of fixed Pt NPs.The prepared Pt nanocatalysts has excellent HER catalytic performance and has good application prospects.