Controllable synthesis of B,N co-doped C from metal-organic frameworks with tunable catalytic performance

Publication Type:
Issue Date:
Full metadata record
Dual heteroatom-doped carbon materials have attracted widespread research attention as catalysts in the field of energy storage and conversion due to their unique electronic structures and chemical tunability. In particular, boron and nitrogen co-doped carbon (B,N@C) has shown great potential for electrocatalytic applications. However, more research is needed in designing and regulating the structure of these materials to improve their catalytic performance. Furthermore, mass transfer is critical in catalytic processes, more so when the reactions are facilitated by nanostructured catalysts. Strong efforts have been devoted to improving the efficacy and quantity of active sites, but often the mass transfer has not been well studied. This thesis aims to develop novel B,N@C nanoreactors with hierarchical porous structures as electrocatalysts that feature high catalytic activities and investigate the importance of mass transfer on the electrocatalyst performance based on these as-obtained nanoreactors. Firstly, monodispersed hierarchical porous B,N@C nanocages are fabricated by pyrolyzing zeolite imidazole framework (ZIF) which is treated with ammonia borane (AB) or boric acid (BA) via an integrated double-solvent impregnation and nanoconfined etching. The treated ZIF-8 provides an essential structural template to achieve hierarchical B,N@C structures with micro/meso/macro multimodal pore size distributions. The resultant B,N@C nanocages display high catalytic activities for electrochemical oxygen reduction reaction (ORR) in alkaline media. Then, mass transfer is regulated in electrocatalytic ORR by tailoring pore sizes. Using a confined-etching strategy, I fabricate B,N@C electrocatalysts featuring abundant active sites but different amounts of micro-, meso- and macropores. The ORR performance of these catalysts is found to correlate with the diffusion of the reactants. The optimized B,N@C with trimodal-porous structures feature enhanced O2 diffusion and better catalytic activity per heteroatomic site toward the ORR process, with the performance being on par with commercial Pt/C. Finally, preliminary results of the preparation of multilevel hollow ZnCo@NCO and ZnCo@NCBO nanoreactors by etching ZnCo-ZIF are reported. The nanoreactor is tested in electrocatalytic oxygen evolution reaction (OER) and electro-oxidation of benzyl alcohol.
Please use this identifier to cite or link to this item: