Preparation And Research Of High Efficiency Electrocatalyst For Hydrogen Evolution With Low Content Of Platinum

The diversification of energy structure is the demand of the development of The Times.However,energy shortage,uneven energy distribution,environmental pollution and resource waste caused by energy transformation become the key.Hydrogen is regarded as one of the most promising new energy sources due to its high energy density and pollution-free products,which can effectively alleviate the environmental pollution caused by fossil fuel combustion.Hydrogen electrolysis of aquatic products is considered as one of the important ways to solve the efficient utilization of renewable energy.By applying electric energy,high-purity hydrogen can be produced on a large scale.However,due to high energy consumption of hydrogen production from direct electrolysis of water,high efficiency catalysts are usually introduced in the process of electrolysis of water to improve production efficiency and reduce energy consumption.The hydrogen evolution is still the most efficient electric catalyst material is given priority to with platinum group as a representative of precious metals,but due to its limited capacity,as well as the expensive price,limits the commercial use of the precious metal catalyst,therefore,the research and development of low dosage,high efficiency,stable platinum compound catalyst for hydrogen evolution,realize the chemical fuel efficient preparation of high purity hydrogen,become a hot topic in the field of clean energy.Based on the above reasons,this paper proposes to design and prepare platinum based electrocatalysts and improve the utilization rate and catalytic efficiency of platinum by using the platinum grain size effect and phase transformation engineering.The main work contents are as follows:（1）Multi-size platinum grains are prepared by light deposition method.The effect of platinum crystals of different sizes anchored on carbon nanotubes on the electrochemical hydrogen evolution and oxygen oxidation reactions was systematically studied.The carbon nanotubes are modified by polydopamine,and Pt nanoclusters are uniformly loaded on the surface of the carbon nanotubes by light deposition.Electrochemical performance tests show that in the full p H range,the Pt catalyst with a size of about 1.5 nm exhibits better HER performance than similar catalysts,and its mass activity is even 23-36 times that of commercial Pt/C.For ORR,the 3nm size Pt catalyst has the best performance,and its mass activity in acidic and alkaline electrolytes is 3 and 16 times that of commercial Pt/C,respectively.The excellent electrocatalytic performance benefits from the SMSI between the Pt and the carbon nanotube matrix and the high surface site to edge site ratio,which significantly improves the catalytic activity and kinetic speed of the catalyst in the catalytic hydrogen evolution reaction.（2）One-step preparation of amorphous platinum-based electrocatalysts.The pyrrole and the chloroplatinic acid solution are mixed,and the spherical amorphous platinum-based electrocatalyst is prepared by a simple one-step synthesis method.Experiments have found that during the electrochemical hydrogen evolution process,the amorphous platinum catalyst will nucleate in situ to form stable platinum clusters.The HER performance also improves with the progress of the electrochemical reaction process.After 50 cycles,the sample has higher catalytic activity for hydrogen evolution in 0.5 M H₂SO₄.When the current density is 10 m A cm^-2,the overpotential drops from 89.7 m V to about 18.8 m V,and the Tafel slope drops to 27.8 m V dec^-1.Combined with spectroscopic characterization,it is found that the amorphous platinum sample forms a Pt-O bond during the transition from amorphous to crystalline state,which accelerates the coupling of electrons and protons and quickly releases H₂,thereby improving the intrinsic activity of the catalyst for the hydrogen evolution reaction and the kinetic speed provides a new idea for further research on the function and application of phase engineering in the regulation of nanomaterials.（3）Synthesis of Pt/W₂C by one-pot pyrolysis.The tungsten carbide precursor was prepared by the soft template cross-linking method,and the platinum acetylacetonate and the tungsten carbide precursor were uniformly mixed and pyrolyzed by the ball milling method to prepare the Pt/W₂C composite material.The experimental results show that the sample heat-treated at 900°C exhibits excellent electrocatalytic activity for hydrogen evolution in acidic electrolytes.When the current density is 10 m A cm^-2,the overpotential is 36.3 m V,and the mass activity is much higher than commercial Pt/C.