Synthesis Of Rhenium-based 2D Nanomaterials For Electrocatalysis

Recently,two-dimensional(2D)nanomaterials have drawn a great deal of attentions due to their remarkable physical and chemical properties.The rhenium-based dichalcogenide materials Re X2(X = S,Se),a new member of the 2D materials,exhibit appealing electronic,vibrational and optical properties,such as the in-plane anisotropic property and the tunable direct bandgap from bulk to monolayer,due to their low crystal symmetry and weak interlayer coupling.According to the recent reports,Re X2 has attracted considerable attention for their great potential in the fields of field-effect transistors,photodetectors,energy storage and photoelectrocatalysis.In such time when people are zealously looking for alternative energy sources,the research on such new-emerging nanomaterials is absolutely significant.Here,we report a facile hydrothermal/solvothermal method to grow Re S2,Re Se2,Re Se2(1-x)S2x and Re O3 nanomaterials,which were applied to the electrocatalytic hydrogen evolution reaction(HER).The main subjects of this thesis are concluded as follows:1.The vertically aligned Re S2 nanosheets with a size of 20-100 nm were prepared on carbon fiber paper(CFP)through hydrothermal method with the precursor of ammonium perrhenate and thiourea.After continuous pre-electrolysis under visible-light irradiation for about 2 h during the electrochemical testing,the activated Re S2 nanosheets performs highly enhanced catalytic activity,with a low overpotential of 116 m V is required to afford the current density of 10 m A cm-2 and a long stability over 10 h.It is worth noting that a significant onset potential decreasing is observed from 170 to 88 m V.Ex-situ transmission electron microscopy(TEM)and inductively coupled plasma emission spectrometer(ICP)examinations demonstrate that the performance improvement is attributed to the defect introduction during the visible-light assisted pre-electrolysis process involving the atoms vacancies,distortions,and the extended interplaner distance.Theoretical calculations further confirm that the defects especially the abundant atoms vacancies activate the inert basal plane as highly active sites for hydrogen evolution.2.In this work,we present an efficient electrocatalyst derived from sulfur-doped rhenium selenide Re Se2(1-x)S2x grown on CFP by a simple solvothermal method for water splitting.It is noting that the catalytic activity could be significantly fine-tuned by controlling the introduced sulfur dopant.The Re Se1.78S0.22/CFP cathode exhibits the best performance with a low overpotential of 123 m V to drive the current density of 10 m A cm-2 as well as a long-term stability of 30 h.The X-ray photoelectron spectroscopy and density functional theory calculations further confirm that sulfur-modified structure,especially the dangling sulfur atoms adsorbed to the surface Se atom kars provides additional active sites and achieves a more thermoneutral hydrogen adsorption energy,conducing an optimized catalytic activity of the basal plane.3.Here,we report a novel hexagonal-phase Re O3 nanostructures electrocatalyst for efficient hydrogen generation.By adjusting the solvent,nanoparticles and nanosheets of Re O3 are successfully synthesized through a facile solvothermal method and exhibit stable electrocatalytic performance in acid electrolyte.A low overpotential of 86 m V and 107 m V are required to drive the current density of 10 m A cm-2 by Re O3 nanoparticles and nanosheets.Excellent conductivity and huge active surface area resulting from the small-sized and high coverage nanostructures contribute to the performance according to the experimental data.