Preparation And Electrocatalytic Investigations Of Bismuth Chalcogenide

Electrocatalyticmaterials play a vital role in the field of conversion and utilization of new energy sources（collecting and transporting electrons and conducting catalytic reaction systems）.Electrocatalyticmaterials that are efficient,clean,non-polluting,and simple to prepare are always the focus of research in the energy field.As amain group element compound,bismuth chalcogenides has the advantages of simple phase,easy preparation,low rawmaterial price,abundant reserves,green and low toxicity.However,the electrocatalytic acitivity of bismuth chalcogenide has rarely been investigated in the past several years.Thus,in our thesis,the preparation and electrocatalytic activity of bismuth chalcogenides,was investigated for its potential applications in dye sensitized solar cells and oxygen reduction.The research contents and results are as follows:1)Ni S nanoparticles and Bi OCl nanosheets（denoted as Ni S/Bi OCl）were prepared by in-situ low-temperature pyrolysis of Ni Cl₂-Bi Cl₃-Tu precursor on FTO conductive substrate under Ar atmosphere using a simple one-step solution low temperature film formationmethod.The obtained Ni S/Bi OCl film can catalyze the reduction of I₃^-at a very low charge transfer resistance of 0.21Ω·cm²,which produces a photoelectric conversion efficiency of 7.88%in the dye-sensitized solar cell,is higher than the same conditions of Pt（7.35%）and low crystalline Ni S（7.64%）.In addition,the Ni S/Bi OCl composite film can also catalyze the oxygen evolution reaction（OER）.At a current density of 10m A/cm²,the electrode potential is 1.61 V,and the Tafel slope is 113m V/dec.Our synthetic approachmakes Ni S/Bi OCl films a cost-effective and efficient electrocatalyst in dye-sensitized solar cells and other clean energy devices.2)Bi₂S₃ thin film was grown in situ on FTO conductive glass and graphite paper by hydrothermalmethod,and Bi₂Se₃ film was prepared by solvothermalmethod.Themicrostructure and electrochemical impedance of Bi₂S₃ films prepared under different hydrothermal conditions were investigated.By controlling the preparation parameters,the charge transfer resistance of Bi₂S₃ films was reduced to 8.52Ω·cm² during electrocatalytic reduction of I₃^-（the literature report>300Ω·cm²）;In addition,the electrochemical properties of Bi₂Se₃ thin films and the performance of dye-sensitized solar cell devices were studied.The charge transfer resistance of Bi₂Se₃ thin films was 4.54Ω·cm² during electrocatalytic reduction of I₃^-.Finally,Bi₂Se₃ was used as the dye-sensitized solar cell counter electrode,and a photoelectric conversion efficiency of 5.88%was obtained.3)Ni₃Bi₂S₂/N-C composites were prepared by pyrolysis of Ni（NO₃）₂-Bi（NO₃）₃-Tu-C₃N₄ precursors at high temperature.Studies have shown that Ni₃Bi₂S₂/N-C powder has the ability to catalyze I₃^-reduction and oxygen reduction.In the electrocatalytic reduction of I₃^-,the interface charge transfer resistance is only 0.55Ω·cm².Finally,as the counter electrode of the dye-sensitized solar cell,the photoelectric conversion efficiency of 6.41%is achieved,which is higher than the Pt under the same conditions（6.14%）.Secondly,when the oxygen reduction reaction was carried out in a 0.1M oxygen-saturated KOH solution,the initial potential was 0.91 V,the half-wave potential was 0.81 V,and the limiting current density was 5.9m A/cm²(Pt/C initial potential was 0.91V,the half-wave potential was 0.85 V and the limiting current density was 5.88m A/cm².Due to the excellent electrical conductivity of Ni₃Bi₂S₂,the Tafel slope of Ni₃Bi₂S₂/N-C is only 47m V/dec,which shows superior oxygen reduction kinetics compared to commercial Pt/C（77m V/dec）.