Browsing by Author "Xia, Chuan"

Now showing 1 - 5 of 5
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    CO2/carbonate-mediated electrochemical water oxidation to hydrogen peroxide
    (Springer Nature, 2022) Fan, Lei; Bai, Xiaowan; Xia, Chuan; Zhang, Xiao; Zhao, Xunhua; Xia, Yang; Wu, Zhen-Yu; Lu, Yingying; Liu, Yuanyue; Wang, Haotian
    Electrochemical water oxidation reaction (WOR) to hydrogen peroxide (H2O2) via a 2e− pathway provides a sustainable H2O2 synthetic route, but is challenged by the traditional 4e− counterpart of oxygen evolution. Here we report a CO2/carbonate mediation approach to steering the WOR pathway from 4e− to 2e−. Using fluorine-doped tin oxide electrode in carbonate solutions, we achieved high H2O2 selectivity of up to 87%, and delivered unprecedented H2O2 partial currents of up to 1.3 A cm−2, which represents orders of magnitude improvement compared to literature. Molecular dynamics simulations, coupled with electron paramagnetic resonance and isotope labeling experiments, suggested that carbonate mediates the WOR pathway to H2O2 through the formation of carbonate radical and percarbonate intermediates. The high selectivity, industrial-relevant activity, and good durability open up practical opportunities for delocalized H2O2 production.
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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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    Highly selective oxygen reduction to hydrogen peroxide on transition metal single atom coordination
    (Springer Nature, 2019) Jiang, Kun; Back, Seoin; Akey, Austin J.; Xia, Chuan; Hu, Yongfeng; Liang, Wentao; Schaak, Diane; Stavitski, Eli; Nørskov, Jens K.; Siahrostami, Samira; Wang, Haotian
    Shifting electrochemical oxygen reduction towards 2e– pathway to hydrogen peroxide (H2O2), instead of the traditional 4e– to water, becomes increasingly important as a green method for H2O2 generation. Here, through a flexible control of oxygen reduction pathways on different transition metal single atom coordination in carbon nanotube, we discovered Fe-C-O as an efficient H2O2 catalyst, with an unprecedented onset of 0.822 V versus reversible hydrogen electrode in 0.1 M KOH to deliver 0.1 mA cm−2 H2O2 current, and a high H2O2 selectivity of above 95% in both alkaline and neutral pH. A wide range tuning of 2e–/4e– ORR pathways was achieved via different metal centers or neighboring metalloid coordination. Density functional theory calculations indicate that the Fe-C-O motifs, in a sharp contrast to the well-known Fe-C-N for 4e–, are responsible for the H2O2 pathway. This iron single atom catalyst demonstrated an effective water disinfection as a representative application.