Browsing by Author "Zhu, Peng"

Now showing 1 - 6 of 6
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    Catalysts Design and Reactor Engineering for Electrochemical CO2 Capture and Utilization
    (2023-08-11) Zhu, Peng; Wang, Haotian
    The rapidly increasing concentration of carbon dioxide (CO2) in the atmosphere has raised serious concerns regarding global climate change. In response to this challenge, the Paris Agreement has set ambitious targets to reduce global greenhouse gas emissions and limit the global temperature increase to no more than 1.5˚C above pre-industrial levels. While international communities have announced ambitious goals for carbon emission reduction during the 2021 Leaders’ Summit on Climate, there is an urgent need for advanced technologies, including carbon capture, conversion, and storage, to effectively neutralize or even reduce CO2 emissions. Significant advancements have been made in renewable grid technologies, enabling the efficient harnessing of green electricity from sources such as solar and wind power. By leveraging these developments, electrochemical CO2 capture and utilization (CCU) have become increasingly attractive as a sustainable and economically viable approach for utilizing CO2 as a valuable resource. The decreasing cost of renewable electricity has made the electrochemical conversion of CO2 into useful chemical feedstocks more economically feasible, opening up new possibilities for mitigating CO2 emissions and advancing the circular carbon economy. In this dissertation, I focus on coupling catalysts design and cell engineering to develop CO2 capture technologies and CO2 electrochemical reduction methods. Our research aims to contribute to the mitigation of CO2 emissions, the capture of carbon as a valuable resource, and the promotion of a more sustainable and low-carbon future. Through the development of various catalysts such as bismuth (Bi), copper (Cu) and single atom catalysts (SACs), as well as novel solid electrolyte reactors, I have successfully achieved the continuous generation of CO gas, pure liquid fuels such as formic acid and acetic acid, and CO2 capture. These advancements offer promising solutions for addressing CO2 emissions and advancing the utilization of CO2 as a valuable feedstock.
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    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.
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    Electrochemical CO 2 reduction to high-concentration pure formic acid solutions in an all-solid-state reactor
    (Springer Nature, 2020) Fan, Lei; Xia, Chuan; Zhu, Peng; Lu, Yingying; Wang, Haotian
    Electrochemical CO2 reduction reaction (CO2RR) to liquid fuels is currently challenged by low product concentrations, as well as their mixture with traditional liquid electrolytes, such as KHCO3 solution. Here we report an all-solid-state electrochemical CO2RR system for continuous generation of high-purity and high-concentration formic acid vapors and solutions. The cathode and anode were separated by a porous solid electrolyte (PSE) layer, where electrochemically generated formate and proton were recombined to form molecular formic acid. The generated formic acid can be efficiently removed in the form of vapors via inert gas stream flowing through the PSE layer. Coupling with a high activity (formate partial current densities ~450 mA cm−2), selectivity (maximal Faradaic efficiency ~97%), and stability (100 hours) grain boundary-enriched bismuth catalyst, we demonstrated ultra-high concentrations of pure formic acid solutions (up to nearly 100 wt.%) condensed from generated vapors via flexible tuning of the carrier gas stream.
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    Highly active and selective oxygen reduction to H2O2 on boron-doped carbon for high production rates
    (Springer Nature, 2021) Xia, Yang; Zhao, Xunhua; Xia, Chuan; Wu, Zhen-Yu; Zhu, Peng; Kim, Jung Yoon (Timothy); Bai, Xiaowan; Gao, Guanhui; Hu, Yongfeng; Zhong, Jun; Liu, Yuanyue; Wang, Haotian
    Oxygen reduction reaction towards hydrogen peroxide (H2O2) provides a green alternative route for H2O2 production, but it lacks efficient catalysts to achieve high selectivity and activity simultaneously under industrial-relevant production rates. Here we report a boron-doped carbon (B-C) catalyst which can overcome this activity-selectivity dilemma. Compared to the state-of-the-art oxidized carbon catalyst, B-C catalyst presents enhanced activity (saving more than 210 mV overpotential) under industrial-relevant currents (up to 300 mA cm−2) while maintaining high H2O2 selectivity (85–90%). Density-functional theory calculations reveal that the boron dopant site is responsible for high H2O2 activity and selectivity due to low thermodynamic and kinetic barriers. Employed in our porous solid electrolyte reactor, the B-C catalyst demonstrates a direct and continuous generation of pure H2O2 solutions with high selectivity (up to 95%) and high H2O2 partial currents (up to ~400 mA cm−2), illustrating the catalyst’s great potential for practical applications in the future.
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    Hydrogen Peroxide Electrosynthesis in a Strong Acidic Environment Using Cationic Surfactants
    (American Chemical Society, 2024) Adler, Zachary; Zhang, Xiao; Feng, Guangxia; Shi, Yaping; Zhu, Peng; Xia, Yang; Shan, Xiaonan; Wang, Haotian
    The two-electron oxygen reduction reaction (2e–-ORR) can be exploited for green production of hydrogen peroxide (H2O2), but it still suffers from low selectivity in an acidic electrolyte when using non-noble metal catalysts. Here, inspired by biology, we demonstrate a strategy that exploits the micellization of surfactant molecules to promote the H2O2 selectivity of a low-cost carbon black catalyst in strong acid electrolytes. The surfactants near the electrode surface increase the oxygen solubility and transportation, and they provide a shielding effect that displaces protons from the electric double layer (EDL). Compared with the case of a pure acidic electrolyte, we find that, when a small number of surfactant molecules were added to the acid, the H2O2 Faradaic efficiency (FE) was improved from 12% to 95% H2O2 under 200 mA cm–2, suggesting an 8-fold improvement. Our in situ surface enhanced Raman spectroscopy (SERS) and optical microscopy (OM) studies suggest that, while the added surfactant reduces the electrode’s hydrophobicity, its micelle formation could promote the O2 gas transport and its hydrophobic tail could displace local protons under applied negative potentials during catalysis, which are responsible for the improved H2O2 selectivity in strong acids.
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    Three-chamber electrochemical reactor for selective lithium extraction from brine
    (National Academy of Sciences, 2024) Feng, Yuge; Park, Yoon; Hao, Shaoyun; Fang, Zhiwei; Terlier, Tanguy; Zhang, Xiao; Qiu, Chang; Zhang, Shoukun; Chen, Fengyang; Zhu, Peng; Nguyen, Quan; Wang, Haotian; Biswal, Sibani Lisa; Rice Advanced Material Institute
    Efficient lithium recovery from geothermal brines is crucial for the battery industry. Current electrochemical separation methods struggle with the simultaneous presence of Na+, K+, Mg2+, and Ca2+ because these cations are similar to Li+, making it challenging to separate effectively. We address these challenges with a three-chamber reactor featuring a polymer porous solid electrolyte in the middle layer. This design improves the transference number of Li+ (tLi+) by 2.1 times compared to the two-chamber reactor and also reduces the chlorine evolution reaction, a common side reaction in electrochemical lithium extraction, to only 6.4% in Faradaic Efficiency. Employing a lithium-ion conductive glass ceramic (LICGC) membrane, the reactor achieved high tLi+ of 97.5% in LiOH production from simulated brine, while the concentrations of Na+ K+, Mg2+, and Ca2+ are below the detection limit. Electrochemical experiments and surface analysis elucidated the cation transport mechanism, highlighting the impact of Na+ on Li+ migration at the LICGC interface.