| Due to the exhaustion of traditional fossil energy sources and serious environmental pollution,there is an urgent need to develop a clean and sustainable alternative energy source,such as solar and hydrogen energy.Hydrogen has the characteristics of high-quality energy density and zero carbon content,and is considered to be the most promising alternative to fossil fuels.At the same time,electrochemical water splitting is considered to be the most far-reaching hydrogen production technology.On the hand,the earth has 70%coverage of water resources.On the other hand,it can generate electricity through wind and solar energy to drive electrolytic water.The water electrolysis process mainly involves hydrogen evolution reaction（HER）on the cathode and oxygen evolution reaction（OER）on the anode.Since the oxygen evolution reaction involves a four-electron transfer process that requires a large overpotential to drive the occurrence of water splitting,it is necessary to use an electrocatalyst to reduce the overpotential and increase the catalytic kinetics of the electrode surface to enhance the water splitting efficiency.Although the precious metals Ir and Ru are generally considered to be the most excellent OER catalysts,the cost,scarcity,poor stability and other problems have severely hindered large-scale practical application.Therefore,it is particularly important to develop sustainable transition metal electrode materials that have the advantages of abundant earth content,low price,and excellent catalytic performance.The transition metal-boron-based catalyst has the advantages of simple preparation process,good stability,and low cost,and has been widely used in the field of electrolysis of water.In this thesis,we design and synthesize the transition metal boron-based oxygen evolution electrocatalyst from the morphology,sample composition,electronic structure,in-depth study the OER electrochemical performance of the catalyst sample,and reveal the mechanism of OER performance enhancement.The specific research content and conclusions are as follows:（1）Using ZIF-67 as precursor and borate buffer solution as boron source,a unique three-dimensional hollow nanocage sample of B-Co3O4@ZIF-67 was prepared by one-step solvothermal method in methanol system.Its unique structure can promote the mass transfer process and expose more catalytic active sites.In addition,the introduction of boron is easy to produce a large number of vacancies,which can effectively adjust the electronic structure of Co atoms and promote the production of more highly oxidized substances.Its unique morphology and electronic control make the B-Co3O4-2@ZIF-67 sample exhibit excellent OER catalytic activity in alkaline medium,and only need 330 m V overpotential when providing a current density of 10m A/cm2,Tafel slope is 73.88 m V/dec,and shows excellent cycle stability.（2）Using Co Fe-MOF with different metal ratios as sacrificial templates,potassium borate and sodium hypophosphite were selected as boron and phosphorus sources,respectively,through two steps of solvothermal boronization and low-temperature phosphating to prepare boron-doped cobalt-iron bimetals phosphide nanosheets.Studies have shown that the higher the content of Co,the easier it is to form a sheet-like structure.When the Co/Fe ratio is 1:1,the prepared Co1-Fe1-B-P nanosheets have excellent OER performance,and have a smaller overpotential（294m V）at 10 m A/cm2 current density,and the Tafel slope is 49.52 m V/dec and has long-term durability.Its excellent catalytic activity can be attributed to the synergy between metal and non-metal to adjust the electronic configuration of the metal center,thereby promoting the generation of high oxidation state active substances and improving the electron transfer ability.（3）Using cobalt nitrate and ferric nitrate as metal sources,potassium tetraborate and sodium hypophosphite as non-metal sources,Co Fe-B-P nanoparticles were synthesized by a simple one-pot solvothermal method.The composition optimization study showed that the Co4Fe1-B-P sample prepared when the ratio of Co/Fe was 4:1and the ratio of sodium hypophosphite was 2.0 mmol had the best OER catalytic performance in 1.0 M KOH,and only an overpotential of 285 m V can provide a current density of 10 m A/cm2.On the one hand,smaller nanoparticles can provide a larger specific surface area and easily expose more catalytically active sites;on the other hand,the synergistic effect between Co and Fe can significantly reduce the charge transfer resistance.In addition,the electronic interaction between metals and non-metals is beneficial to form more MOOH intermediate products,thereby significantly enhancing the OER activity of the catalyst. |
