Fall 2021 PhD Seminar Two

NiN₄ moieties embedded in partially graphitized carbon are recognized as one of the effective active sites in Ni-N-C materials for CO₂ electroreduction to CO. However, much mystery remains behind the intrinsic factor underlying their coordination environment that contribute to their phenomenal performance. We systematically elucidated the structural evolution of NiN₄ sites during thermal activation by using a Ni-N-C model catalyst derived from zeolitic imidazolate framework (ZIF)-8-based materials. The varying N coordination, metal-N bond length, thermal wrinkling of graphene, vacancies and defects densities induced by thermal evaporation and other intrinsic factors were carefully disemminated. Accompanying this fundamental study, we also studied how morphological factors such as the particle size of the carbon host and the loading of Ni alter their structure and performance. Concluding these thorough study, a remarkable catalytic performance approaching 92.3 mA cm^–2 at –0.9 V vs RHE in H-cell configuration was achieved. Furthermore, the implementation of this catalyst with a flow-cell electrolyze further boasts an impressive selectivity for CO generation with faradaic efficiency for CO above 90% for jCO up to 704.3 mA cm^-2.

BIO

Nadia obtained her bachelor’s degree in Chemical Engineering in 2017 and is currently pursuing a PhD degree from the State University of New York at Buffalo. She is working on electrochemistry and thermocatalysis-related projects. Her current electrochemistry research encompasses cathode development for electrochemical reduction of CO2 into CO/syngas and other valuable C1 products, with emphasis on single atom catalysis, metal-organic framework-derived carbon nanostructures and carbon nanoengineering whereas for thermocatalysis, her research focuses on the development of low-cost transition-metal-based catalyst for ammonia cracking for on-site hydrogen generation.

• Time: 11.30 AM
• Location: 206 Furnas Hall
• Seminar Flyer

Three-way catalysts (TWCs, contain Rh, Pd, Pt), which can simultaneously oxidize carbon monoxide (CO), hydrocarbons (HCs), and reduce nitrogen oxides (NO_x) at temperatures > 350 ^oC, have been successful for gasoline vehicles emissions control in the past decades.  However, with the development of highly efficient engines (lower emission temperatures) and increasing cost of Rh, developing new Rh-free TWCs with enhanced low temperature activity and durability is highly desirable.  Conventional Pt-only TWCs, e.g. Pt/Al₂O₃, Pt/CeO₂, suffer from deactivation after redox hydrothermal aging (800 ^oC/10 h) due to Pt or CeO₂ sintering.  Herein, we demonstrate a facile strategy to enhance the low temperature activity and durability of Pt-only TWCs by anchoring CeO₂ nanocrystals on penta-site rich γ-Al₂O₃ nanosheets (AlNS) with Pt deposited on CeO₂.  Detailed characterizations showed that AlNS incorporation can slow down the CeO₂ nanocrystal grain growth, attributed to the interaction between CeO₂ and AlNS.  Moreover, the majority of Pt can be maintained as Pt nanoclusters when the optimum CeO₂ coverage (60 wt.%) on AlNS is used.  Pt nanoclusters, rather than large Pt particles, are the most active Pt species for TWC applications.  Pt-60%Ce-AlNS showed a comparable performance to the state-of-the-art Rh-based catalyst (Rh/TiAl).  Overall, this work illustrates that CeO₂ deposition on the surface of penta-site rich γ-Al₂O₃ nanosheets can remarkably enhance the catalyst low temperature activity and stability upon redox hydrothermal aging. 

BIO

Junjie Chen received his BSc from Zhejiang University of Technology and master’s degree from Zhejiang University, China.  He is currently pursuing a Ph.D. in Heterogeneous Catalysis under the supervision of Prof. Eleni Kyriakidou at the University at Buffalo (Chemical Engineering), The State University of New York (SUNY).  His current research focuses on developing a fundamental understanding of the function of catalytic materials for vehicle emission remediation.  The emissions control catalysts he developed include CH₄ oxidation catalysts, diesel oxidation catalysts, three-way catalysts, and passive NOx absorbers.  He is also working on H₂ generation from dry reforming of methane and NH₃ decomposition, as well as oxidative dehydrogenation of propane to propylene.