Study On The Controllable Synthesis Of Bismuth-Cobalt Based Nanomaterials And Their Performances In Electrocatalytic Water Splitting

With the increasingly serious environmental pollution and energy demand,the development of sustainable clean energy as a substitute for traditional fossil fuels has become more and more important.The use of electricity generated by solar radiation,wind energy,tidal energy and nuclear fusion to produce hydrogen by water splitting has attracted much attention.Pt-based and RuO2 and IrO2-based noble metals are excellent catalysts for hydrogen evolution reaction(HER)and oxygen evolution reaction(OER),respectively.Although the electrocatalytic performance of noble metals is excellent,their high cost and rarity limit their wide application.In recent years,various non-noble metal catalysts based on low cost and rich earth content have been developed for electrocatalysis of HER and OER.The use of non-precious metal catalysts can effectively reduce production costs and improve the efficiency of electrolysis of water,thereby realizing industrial applications.In this thesis,bismuth(Bi)nanosheets are selected as the base material,BiCo alloy and BiCo2(OH)3Cl-CeO2 catalysts are obtained by electrochemical deposition technology,which are served as electrocatalysts for electrocatalytic HER and OER in alkaline.Subsequently,the electrocatalytic performances were further improved by optimizing the preparation conditions of the catalysts.The main work is as follows:1.Using bismuth oxychloride(BiOCl)nanosheets as Bi source,bismuth-cobalt alloy(BiCo)was synthesized in one step through in-situ electrochemical reduction method.The optimized BiCo electrocatalyst exhibits excellent electrocatalytic activity in 1.0 mol/L KOH.229 mV and 326 mV were required to achieve a current density of 10 mA/cm2 for HER and OER,respectively.BiCo alloy also has long-term durability and can maintain minimal activity loss during continuous electrolysis for up to 20 hours.In addition,BiCo alloy,as a dual-function electrocatalyst,required 1.65 V to obtain a current density of 10 mA/cm2 for overall water splitting.The extremely high electrocatalytic performance of BiCo alloy is attributed to the two-dimensional Bi nanosheets improve the conductivity and electrochemical surface area of the catalyst.The introduction of metal Co provides adsorption sites for Hads and accelerates the charge transfer kinetics of the catalyst.The Co transfers electrons to Bi,regulates the electronic structure of Bi,and reduces the binding energy of Bi-H.The HER process is dominated by the Volmer/Heyrovsky mechanism.The discharge of water molecules in the solution on the surface of the catalyst to generate Hads is a quick step.The introduction of Co enhances the binding capacity of Co and OH-,thereby accelerating the OER reaction kinetics.Moreover,the interface resistance is effectively reduced,the charge transfer rate is increased,which accelerates the charge transfer kinetics and improves the electrocatalytic performance.2.the precursor of bismuth oxide(Bi2O3)nanosheets was prepared by a simple hydrothermal method,and then the BiCo2(OH)3Cl-CeO2 was generated by electrodeposition.When the BiCo2(OH)3Cl-CeO2 was used as an electrocatalyst for OER in alkaline,it has excellent catalytic performance,requiring 146 mV to achieve 10 mA/cm2,and 31 mV/dec of the Tafel slope.In addition,the material exhibits long-term resistance.The current density remains basically unchanged after 20 h of OER test.The electrons of Bi and CeO2 transfer to CO2(OH)3Cl to form abundant oxygen vacancies,which is conducive to the formation of reaction intermediates on the surface of the material,so that the catalytic activity of BiCo2(OH)3Cl-CeO2 is greatly improved.In addition,Cl-undergoes lattice etching and a gradual phase reconstruction to form new active materials during the electrocatalytic OER process,which is beneficial to the electrocatalytic OER.This work proposes a novel and feasible method for designing efficient and stable OER catalysts.3.We futher established an efficient Pt/C‖BiCo2(OH)3Cl-CeO2 electrolyzer for high performance seawater electrolysis by pairing Pt/C HER catalyst with a good BiCo2(OH)3Cl-CeO2 OER catalyst.The electrolyzer demonstrates excellent electrocatalytic activity and stability in alkaline conditions(1.0 mol/L KOH)and simulated seawater(1.0 mol/L KOH+0.5 mol/L NaCl).In two different electrolytes,the Pt/C‖BiCo2(OH)3Cl-CeO2 electrolyzer exhibits excellent overall water splitting performance with cell voltages of 1.62 V and 1.59 V required to achieve current densities of 10 mA/cm2,respectively,which is better than that of precious metal Pt/C‖IrO2 electrolyzer.Besides,it shows excellent stability.