Growing energy demand has stimulated research into cheap, safe and sustainable energy storage and conversion materials. Transition metal-based catalytic materials have been widely used in electrocatalysis due to their abundant reserves, low price, unique 3d electronic structure, and tunable compositions. Structural control and electronic modification are two important approaches to reduce the overpotential for electrocatalytic water splitting.
The construction of architectures can expose specific active surfaces, improve mechanical stability, create a large number of ion diffusion channels, and enhance reaction kinetics, thereby greatly improving the apparent catalytic activity. Specifically, (i) dodecagonal PdCoNi carbon-based nanosheets were synthesized by an ammonia-assisted in-situ cation exchange method; (ii) a core-shell PBA was prepared by iterative wrapping, which was activated using anodization for water splitting; (iii) ultra-high specific surface area Fe3O4/NiCx porous composites were synthesized using a sol-gel method to optimize the adsorption intermediates of seawater splitting.
The modulation of electronic structure can optimize the band structure and energy of adsorption intermediates, thereby enhancing the intrinsic activity of electrocatalysts. Specifically, (i) inverse opal framework hematite containing oxygen vacancies was combined with gold nanostars to take advantage of their synergistic effect to enhance EC and PEC water oxidation; (ii) metal cations were used as structure directing agents to modulate the structure of Cl-doped Co compounds, which were subsequently annealed to hierarchical Co3O4 with Cl-heteroatom doping; (iii) lattice strain was introduced into Bi2S3 with 3D hierarchical structure by topological transformation method to change the electronic structure.
The thesis combines materials synthesis, characterizations and DFT calculations with performance testing to provide insights into the relationship between structural design, electronic modification and electrocatalytic performance, which can be enlightening for the design and application of future 3d transition metal-based electrocatalysts.