Browsing by Author "Chen, Feng-Yang"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Electrochemical ammonia synthesis via nitrate reduction on Fe single atom catalyst
    (Springer Nature, 2021) Wu, Zhen-Yu; Karamad, Mohammadreza; Yong, Xue; Huang, Qizheng; Cullen, David A.; Zhu, Peng; Xia, Chuan; Xiao, Qunfeng; Shakouri, Mohsen; Chen, Feng-Yang; Kim, Jung Yoon (Timothy); Xia, Yang; Heck, Kimberly; Hu, Yongfeng; Wong, Michael S.; Li, Qilin; Gates, Ian; Siahrostami, Samira; Wang, Haotian; Bioengineering; Chemical and Biomolecular Engineering; Civil and Environmental Engineering; Statistics
    Electrochemically converting nitrate, a widespread water pollutant, back to valuable ammonia is a green and delocalized route for ammonia synthesis, and can be an appealing and supplementary alternative to the Haber-Bosch process. However, as there are other nitrate reduction pathways present, selectively guiding the reaction pathway towards ammonia is currently challenged by the lack of efficient catalysts. Here we report a selective and active nitrate reduction to ammonia on Fe single atom catalyst, with a maximal ammonia Faradaic efficiency of ~ 75% and a yield rate of up to ~ 20,000 μg h−1 mgcat.−1 (0.46 mmol h−1 cm−2). Our Fe single atom catalyst can effectively prevent the N-N coupling step required for N2 due to the lack of neighboring metal sites, promoting ammonia product selectivity. Density functional theory calculations reveal the reaction mechanisms and the potential limiting steps for nitrate reduction on atomically dispersed Fe sites.
  • Thumbnail Image
    Item
    Electrochemical Synthesis of Green Hydrogen and Ammonia via Catalyst Design and Electrolyzer Engineering
    (2024-08-06) Chen, Feng-Yang; Wang, Haotian
    The rapid increase in atmospheric carbon dioxide levels has become a pressing concern for global climate change. Electrocatalysis has emerged as a critical pathway for decarbonizing chemicals and fuels, particularly in the production of hydrogen and ammonia, given the intensive carbon emissions associated with conventional chemical engineering plants. In this thesis, we systematically address the current challenges within electrocatalytic water splitting and nitrate reduction reactions, which are critical processes for green hydrogen and ammonia synthesis. We first investigated mechanistic insights into the stability challenges of oxygen evolution reaction catalysts, alongside practical considerations for reactor design. A non-iridium-based electrocatalyst was then developed to reduce costs and enhance durability for the acidic oxygen evolution reaction, integrated into a proton exchange membrane electrolyzer to facilitate efficient green hydrogen production. Additionally, we investigated an oxide alloy catalyst system aimed at further reducing noble metal loading while enhancing catalyst activity. Furthermore, we examined electrochemical nitrate reduction as an alternative pathway for green ammonia production, focusing on the design and synthesis of catalysts for efficient conversion. Moreover, we designed a solid electrolyte reactor and coupled it with a cation shuttling process to advance the direct conversion of waste nitrate streams into green ammonia. The catalyst design and electrolyzer engineering strategies proposed in this dissertation contribute meaningfully to the development of electrochemical technologies crucial for sustainable energy and resource management.