Preparation Of Biomass-based Anode Electrocatalyst And Study On Its Oxygen Evolution Reaction Activity

As a green secondary energy source,hydrogen energy has been widely used in the automotive field for many years.The rise of hydrogen energy can help to cope with the current energy and environmental tensions.It is a very promising clean energy in the long term.Electrolytic water hydrogen production technology is an effective way to convert hydrogen energy.However,due to the slow reaction kinetics in the oxygen evolution reaction（OER）of the anode,it has become a major obstacle to the conversion efficiency.Therefore,it is especially important to study and develop a low-cost,high-efficiency and stable oxygen evolution electrocatalyst.Natural biomass wood has a unique ordered pore structure,low cost and environmental friendliness.The internal pore structure and specific surface area can directly affect the electrochemical performance.The anode carrier of biomass wood as the oxygen evolution reaction electrocatalyst has rarely been reported.Therefore,this paper mainly uses the ordered porous structure of natural biomass wood,and through the experimental screening of wood with different air dry density,The in-situ reduction method and hydrothermal synthesis-in-situ reduction method were used to construct basic anode catalyst with excellent oxygen evolution performance of loading Fe/Co bimetallic on carbonized wood（Wood Carbon,WC）（FeCo@WC）and Ni/Fe bimetallic（N-NiFe@WC）supported on carbonized wood under N doping.which effectively reduces the overpotential in the OER process,reduces energy consumption,and improves hydrogen production efficiency.The main research contents of this thesis are as follows:（1）Four kinds of anodes loading with Ni catalyst particles were prepared by in-situ thermal reduction method by selecting natural biomass wood with different air dry density.After nitrogen adsorption/desorption（BET）and X-ray diffraction（XRD）characterization,it was found that the carbonized black walnut had a very large specific surface area（954.41m²/g）and lower degree of graphitization degree（0.99）.By studying its oxygen evolution catalytic ability,the catalytic ability of H-Ni@WC（H means black walnut）is significantly higher than that of other woods,mainly because black walnut has a very large With a specific surface area and dense ordered porous curved channels,this natural pore structure provides a fast channel for the diffusion and transport of substances and increases the active site.This wood has become an important anode carrier material for the preparation of other catalysts in this experiment.（2）Using the advantages of natural black walnut structure,FeCo@WC anode catalyst prepared by in-situ thermal reduction loading of bimetal,the structure and surface chemistry of bimetallic Fe/Co were determined by XRD and X-ray photoelectron spectroscopy（XPS）analysis.The distribution and content of the catalyst elements were analyzed by scanning electron microscope（SEM）and Energy Dispersive X-Ray Spectroscopy（EDS）.The electrochemical experiments show that the FeCo@WC catalyst has very good oxygen evolution performance and stability in 0.1 M Na OH solution,and the overpotential is as low as 220 m V at a current density of 10 m A cm^-2,and the Tafel slope was 59 m V dec^-1.After 26h of stability test,the activity was not significantly reduced.The main reason is that in addition to the large specific surface area,the active site can be increased,and the flexibility of the channel in the black walnut can be well protected without adding any binder.The catalyst particles are deactivated during the electrochemical process,which improves the long-term stability of the catalyst.（3）N-NiFe@WC anode catalyst was prepared by hydrothermal synthesis-in-situ reduction method.It was found by nitrogen adsorption/desorption（BET）that nitrogen doping did not affect the specific surface area and pore diameter of carbonized wood（WC）.It shows that the pore structure of WC is very stable.The SEM observation shows that the Ni₃Fe nanoparticles are uniformly distributed on the WC and the size is uniform.The structure and surface valence of the catalyst are analyzed by XRD and XPS,and the N content is analyzed semi-quantitatively.Electrochemical experiments show that the oxygen evolution performance of the sample in 0.1 M Na OH solution is significantly improved,the overpotential at a current density of 10 m A cm^-2 is 370 m V,and the Tafel slope is 48 m V dec^-1,After 24 hours of stability testing,the activity was only reduced by less than 5%,Mainly because the curved channel structure of wood can effectively anchor the catalyst nanoparticles and doped N atoms to regulate the electron withdrawing/electron-donating ability of the carbon carrier,promote the electron transfer in the catalytic reaction,and improve Conductivity,which facilitates OER catalytic activity and conductivity.