Cobalt And Nickel-Based Classification Hetero Interface Enhanced Electrocatalytic Water-Splitting Performance Study

Generating high-purity and high-energy density H₂ was efficiently achieved by the technology of water splitting in electrolyzer,which could satisfy the needs of economic and social development in the current industrial production and life standard.The key problems in water splitting could deeply explored and solved by the combination of material,physics and electrochemistry.Building a heterogeneous interface with special electrochemical properties at the molecular scale is an effective strategy for improving the electrocatalytic activity of materials,which could achieve a synergistic catalytic effect between the components and the interface.Based on above analysis,this dissertation elaborates that the structures of Co-Ni-based aggregated spheres were synthesized with different heterogeneous interface components,achieving the control of the structure and properties for heterogeneous interface.Meanwhile,it was sudied with the preparation methods of the catalyst,component control of interface,growth mechanism and water splittig performance,including the following three parts:（1）Adjust the ratio of components to construct Co₃O₄/NiO heterogeneous interface to enhance water splitting performance.Under hydrothermal condition,the small difference between the nucleation rate of Co²⁺/Ni²⁺in an alkaline environment was used to prepare heterogeneous aggregates by disordered accumulation of Co/Ni oxyhydroxide nanosheets and nanoblocks.After annealing,the two components in the Co/Ni precursors are respectively transformed into smaller-sized Co₃O₄ nanoparticles and NiO nanorings.During the formation process,there is a tendency of aggregation among the Co₃O₄nanoparticles with high surface energy.Along the opposite direction of the aggregation,the NiO nanorings trend to the surface position of the aggregates.Then the active interface with strong interaction（the displacement characterization of Raman and XPS）was constructed between the two molecules through the Co-O-Ni cross-linking bond,that is,the difference in the force between the metal-oxide molecules could realize the construction of the hierarchical structure of the interface,which could enhance the electrocatalytic performance.（2）Adjust the reduction temperature to construct the M/Ni（M=NiCoO_x,Co）dual system heterogeneous interface to optimize the performance of electrolyzed water.The Co₃O₄/NiO aggregates as the precursors in the first work was reduced to the M/Ni（M=NiCoO_x,Co）heterogeneous interface in a H₂ atmosphere under varied temperatures.With temperature lower than 400℃,NiO NRs were first partially reduced to metallic Ni,and Co₃O₄ NPs was partially reduced to low-priced cobalt oxide;Above 400°C,all are Co/Ni.The result proves that compared to work one,the improved M/Ni（M=NiCoO_x,Co）dual-system catalyst shows good electrolysis performance.（3）Adjust the degree of low-temperature phosphating to build Co-Ni bimetallic phosphide aggregates to promote water splitting.We use Co₃O₄/NiO aggregates as the precursors in the first work,and phosphide aggregates with different compositions were obtained through different degrees of phosphating.As the degree of phosphating increases,different states of composition distribution begin to appear in the aggregates.This is significant to the exposure and optimization of effective active sites which could promote the improvement of the water splitting.