Can electric fields drive chemistry for an aqueous microdroplet?

Hao, Hongxia; Leven, Itai; Head‐Gordon, Teresa

doi:10.1038/s41467-021-27941-x

Cited by 144 publications

(181 citation statements)

References 67 publications

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“…14−18 This may be attributed to the strong electric field across the GLI. 19,20 In this study case, we even observed that the TEMPO was reduced by losing its oxyl group (m/z 142) or hydrogenated to form the ions at m/z 157 and 158 (Figure 3a). These results also proved the special redox environment of the GLI and its critical role in the CO 2 reduction.…”

mentioning

confidence: 60%

Spraying Water Microdroplets Containing 1,2,3-Triazole Converts Carbon Dioxide into Formic Acid

2022

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We report the use of 1,2,3-triazole (Tz)-containing water microdroplets for gas-phase carbon dioxide (CO 2 ) reduction at room temperature. Using a coaxial sonic spraying setup, the CO 2 can be efficiently captured by Tz and converted to formic acid (HCOOH; FA) at the gas−liquid interface (GLI). A mass spectrometer operated in negative ion mode monitors the capture of CO 2 to form the bicarbonate anion (HCO 3 − ) and conversion to form the formate anion (HCOO − ). Varied FA species were successfully identified by MS/MS experiments including the formate monomer ([FA − H] − , m/z 45), the dimer ([2FA − H] − , m/z 91; [2FA + Na − 2H] − , m/z 113), the trimer ([3FA − H] − , m/z 137), and some other adducts (such as [FA − H + H 2 CO 3 ] − , m/z 107; [2FA + Na − 2H + Tz] − , m/z 182).The reaction conditions were systematically optimized to make the maximum conversion yield reach over 80% with an FA concentration of approximately 71 ± 3.1 μM. The mechanism for the reaction is speculated to be that Tz donates the proton and the hydroxide (OH − ) at the GLI, resulting in a stepwise yield of electrons to reduce gas-phase CO 2 to FA.

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confidence: 60%

Spraying Water Microdroplets Containing 1,2,3-Triazole Converts Carbon Dioxide into Formic Acid

2022

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“…If we assume that this potential acts over 5 × 10 −8 cm, this corresponds to an electric field of 2 × 10 7 to 4 × 10 7 V/cm. Recently, Head-Gordon and coworkers ( 44 ) calculated that the electric field alignments along free O–H bonds at the AWI are ∼1.6 × 10 7 V/cm larger on average than that found for O–H bonds in the interior of the water droplet. This estimate is in good agreement with the measured electric field strength of a water microdroplet in oil ( 45 ).…”

Section: Resultsmentioning

confidence: 90%

Sprayed water microdroplets containing dissolved pyridine spontaneously generate pyridyl anions

Zhao

Song

Gong

et al. 2022

Proc. Natl. Acad. Sci. U.S.A.

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Significance Water microdroplets can accelerate chemical reactions by orders of magnitude compared to the same reactions in bulk water and/or trigger spontaneous reactions that do not occur in bulk solution. Among the properties of water microdroplets, the unique redox ability resulting from the spontaneous dissociation of OH − into a released electron and •OH at the air–water interfaces is especially intriguing. At the air–water interface, OH − exhibits a strong reducing potential, and the resulting •OH is highly oxidative, making water microdroplets a unity of opposites. We report the reduction of pyridine into pyridyl anions (C 5 H 5 N − ) and the oxidation of pyridine into hydroxypyridine, which extends what we know about the redox power of water microdroplets.

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“…Other interfacial effects have been considered in explaining observed reaction acceleration ( Fallah-Araghi et al, 2014 ; Yan et al, 2016 ; Lee et al, 2017 , 2019a , 2019b , 2020 ; Zhou et al, 2018 ; Wei et al, 2020 ; Xiong et al, 2020 ; Huang et al, 2021 ), including the extreme pH at the droplet surface ( Basuri et al, 2020 ; Huang et al, 2021 ), preferential orientation of reactants ( Zhou et al, 2018 ; Narendra et al, 2020 ), and strong electric fields (on the order of MV/cm) at or near the microdroplet interface ( Lee et al, 2019b , 2020 ; Xiong et al, 2020 ). The existence of the strong fields is supported by spectroscopic ( Xiong et al, 2020 ) and computational ( Leung, 2010 ; Kathmann et al, 2011 ; Yesibolati et al, 2020 ; Hao et al, 2022 ) data for aqueous microdroplets. The electric field lowers the energy barrier for reaction by stabilizing the transition state or by activating the reactant.…”

Section: Introductionmentioning

confidence: 82%

Spontaneous Water Radical Cation Oxidation at Double Bonds in Microdroplets

et al. 2022

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Spontaneous oxidation of compounds containing diverse X=Y moieties (e.g., sulfonamides, ketones, esters, sulfones) occurs readily in organic-solvent microdroplets. This surprising phenomenon is proposed to be driven by the generation of an intermediate species [M+H2O]+·: a covalent adduct of water radical cation (H2O+·) with the reactant molecule (M). The adduct is observed in the positive ion mass spectrum while its formation in the interfacial region of the microdroplet (i.e., at the air-droplet interface) is indicated by the strong dependence of the oxidation product formation on the spray distance (which reflects the droplet size and consequently the surface-to-volume ratio) and the solvent composition. Importantly, based on the screening of a ca. 21,000-compound library and the detailed consideration of six functional groups, the formation of a molecular adduct with the water radical cation is a significant route to ionization in positive ion mode electrospray, where it is favored in those compounds with X=Y moieties which lack basic groups. A set of model monofunctional systems was studied and in one case, benzyl benzoate, evidence was found for oxidation driven by hydroxyl radical adduct formation followed by protonation in addition to the dominant water radical cation addition process. Significant implications of molecular ionization by water radical cations for oxidation processes in atmospheric aerosols, analytical mass spectrometry and small-scale synthesis are noted.

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Can electric fields drive chemistry for an aqueous microdroplet?

Cited by 144 publications

References 67 publications

Spraying Water Microdroplets Containing 1,2,3-Triazole Converts Carbon Dioxide into Formic Acid

Spraying Water Microdroplets Containing 1,2,3-Triazole Converts Carbon Dioxide into Formic Acid

Sprayed water microdroplets containing dissolved pyridine spontaneously generate pyridyl anions

Spontaneous Water Radical Cation Oxidation at Double Bonds in Microdroplets

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