Preparation Of Graphene-based High Entropy Alloy And Its Application In Hydrogen Production From Water Decomposition

Among the various energy sources,hydrogen energy is considered as an excellent alternative to traditional fossil fuels due to its high energy density and environmental friendliness.Electrolysis of water not only converts electrical energy into chemical energy in an environmentally friendly way,but also be easily combines with other intermittent energy sources（e.g.solar energy）,offering a promising solution for high-purity hydrogen production.However,hydrogen precipitation reactions require a large driving overpotential,resulting in high energy consumption,so the rational selection of efficient catalytic materials has become a research priority.High-entropy alloys are of interest because of their easily tunable components and high catalytic activity.In this work,graphene-based high-entropy alloy materials with different components are prepared by a bottom-up chemical method of metal salt precursor reduction,and the electronic grouping is adjusted to improve the catalytic activity by adjusting the components and compounding.Characterization using scanning electron microscopy,X-ray diffraction,X-ray photoelectron spectroscopy and electrochemistry was used to investigate the morphological structure,hydrogen precipitation properties,electrochemical properties and reaction mechanisms of catalytic materials.The findings of the thesis are as follows:（1）The materials were prepared by rapid pyrolysis（R-Fe Co Ni Cu Sn/GO,R-Fe Cu Ni,R-Fe Co Ni and R-Cu/GO）and programmed temperature（S-Fe Co Ni Cu Sn/GO）using a"bottom-up"metal salt precursor reduction chemistry,and were tested electrochemically using The above materials were used as catalysts for electrochemical tests to evaluate the performance of the high-entropy alloy nanomaterials in decomposing water for hydrogen precipitation.The entropy of the catalytic material increases from low,medium to high as the metal grouping increases from mono-,ternary to quintuplets,thus showing a clear difference in catalytic activity.The results showed that the catalysts exhibit good activity in both acidic and alkaline media.The material R-Fe Co Ni Cu Sn/GO showed an overpotential of 180 m V at a current density of 10 m A cm^-2 with an electrolyte of 0.5 M H₂SO₄ and better hydrogen precipitation performance with an electrolyte of 1 M KOH,requiring an overpotential of only 141 m V at a current density of 10 m A cm^-2.After constant potential testing and 1000 CV cycles,the hydrogen precipitation performance has not deteriorated significantly and the material has good stability.（2）Graphene-based high-entropy alloy materials（R-Fe Cu Ni Co Pt/GO,R-Fe Cu Ni Co Au/G-O and R-Fe Cu Ni Au Pt/GO）containing noble metal nanoparticles were prepared by modulating the composition of the high-entropy alloy elements.It was found that the best catalytic effect was achieved when both precious metals Au and Pt were present in the whole system,with an overpotential of 120 m V and 95 m V required for a current density of 10 m A cm^-2 when the electrolyte was 0.5 M H₂SO₄ and 1 M KOH,respectively.This is attributed to an increase in the amount of noble metal and a gradual increase in the number of active sites on the catalyst surface,the more H intermediates are adsorbed and thus more H₂ is produced increasing the catalytic efficiency.（3）In order to effectively utilize visible light,improve the performance of hydrogen precipitation by decomposing water and reduce the energy consumption of the reaction,the graphene-based high-entropy alloy（R-Fe Co Ni Cu Sn/GO）is compounded with the conventional semiconductor g-C₃N₄.The catalyst was tested under both light and dark conditions and the results showed an instantaneous drop in photocurrent of around 1 m A cm^-2 when the light beam irradiation was stopped and an instantaneous recovery in photocurrent density once the light was restored.The material showed a significant improvement in performance under light conditions,with a difference of about 170 m V from the overpotential under dark conditions.This study provides a viable reference direction for photocatalysis.