- Email: [email protected]
Fish the Oxygen Intermediates
Energy and Emissions Reduction, Industrial Technology Program (United States Department of Energy, Energy Efficiency and Renewable Energy). 4. Markowski, M., and Urbaniec, K. (2005). Online Cleaning Schedule for Heat Exchangers in a Heat Exchanger Network – The Case of Crude Distillation Unit. Proceedings of 6th International Conference on Heat Exchanger Fouling and Cleaning - Challenges and Opportunities. ECI symposium series, Volume RP2. Eds. Hans Mu¨ller-Steinhagen, M. Reza Malayeri, and A. Paul Watkinson, Engineering Conferences International, Germany, June 5–10, 2005.
5. Bui, M., Adjiman, C.S., Bardow, A., Anthony, E.J., Boston, A., Brown, S., Fennell, P.S., Fuss, S., Galindo, A., Hackett, L.A., et al. (2018). Carbon Capture and Storage (CCS): the way forward. Energy Environ. Sci. 11, 1062–1176. 6. Davis, S.J., Lewis, N.S., Shaner, M., Aggarwal, S., Arent, D., Azevedo, I.L., Benson, S.M., Bradley, T., Brouwer, J., Chiang, Y.-M., et al. (2018). Net-zero emissions energy systems. Science 360, eaas9793. 7. 14th International Conference on Greenhouse Gas Control Technologies (GHGT 14). 21–26 October 2018. Melbourne, Australia.
8. Jacobson, M.Z., Delucchi, M.A., Cameron, M.A., and Frew, B.A. (2015). Low-cost solution to the grid reliability problem with 100% penetration of intermittent wind, water, and solar for all purposes. Proc. Natl. Acad. Sci. USA 112, 15060–15065. 9. Clack, C.T.M., Qvist, S.A., Apt, J., Bazilian, M., Brandt, A.R., Caldeira, K., Davis, S.J., Diakov, V., Handschy, M.A., Hines, P.D.H., et al. (2017). Evaluation of a proposal for reliable low-cost grid power with 100% wind, water, and solar. Proc. Natl. Acad. Sci. USA 114, 6722–6727. 10. Webb, R.. The Economics of Star Trek. https://medium.com/@RickWebb/theeconomics-of-star-trek-29bab88d50.
Preview
Fish the Oxygen Intermediates Rose Changrong Zhu1,* Figuring out the oxygen intermediates in the oxygen evolution reaction (OER) process is vital to its full understanding. Efficient and prompt capture of oxygen intermediates has been a challenging research topic. In this issue of Joule, Bin Liu, Jingguang Chen, and colleagues developed an operando technique to probe the OH*, the first intermediate in the OER process. They found that the OH* is electrophilic. Inspired by the preferred combination of electrophiles and nucleophiles, they applied nucleophilic bait to catch the OH*. A clear sign is given by the current difference in the linear sweep voltammetry curve when alcohols such as methanol are added. This efficient in situ probing of oxygen intermediates opens a door for exploring the oxygen-involved process in energy storage and conversion research. Oxygen evolution reaction (OER) is part of various important energy conversion processes—for instance, water splitting, metal air battery, methanol oxidation, etc. Electrocatalysis of water oxidation is a dominating way to obtain hydrogen fuel, while OER is the more sluggish reaction in this process, contributing to a majority of the overpotential needed to drive the reaction. Knowing the exact reaction steps, particularly the rate-determining step, can help advise the catalyst design, which should be the most efficient way to reduce the overpotential of OER. Undoubtedly, oxygen intermediates are the most important information in understanding the OER mechanisms. Therefore, plenty of efforts are spent
on detecting the oxygen intermediates in OER fundamental research. It is noteable that early research has been focused on using spectroscopic techniques for in situ probing. Fourteen years ago, X-ray absorption measurements during fuel cell operation provided the first clue of the O[H] and CO coverage and adsorption sites on PtRu electrodes.1 Meanwhile, surfaceenhanced infrared reflection-absorption spectroscopy with an attenuated total reflection configuration was used to identify the intermediates of the oxygen reduction reaction (ORR) on gold electrodes.2 Continuously, in situ infrared spectroscopy is applied to probe the surface chemistry of a commercial carbon-supported Pt nanopar-
1408 Joule 3, 1404–1414, June 19, 2019 ª 2019 Published by Elsevier Inc.
ticle catalyst during oxygen reduction. The IR spectra show potential-dependent appearance of adsorbed superoxide and hydroperoxide intermediates on Pt.3 Not limited in noble metal, recent research caught the Fe(VI) in nonaqueous solution during water oxidation process utilizing the in situ infrared, UV-visible, Raman, luminescence, and Mo¨ssbauer spectroelectrochemistry techniques.4 However, those spectroscopic techniques need a high vacuum environment and other special conditions, making it less approachable. In addition, they are less efficient for studying aqueous media. Unlike previous research, Tao et al.5 propose an electrochemical way to study the OER reaction process. Their work is inspired by the unique phenomena that carbon monoxide (electrophilic) irreversibly adsorbed on an Au(111) surface acts as a promoter for the electrocatalytic oxidation of methanol6 and the deprotonation process of alcohols in the alkali solutions.7 Tao et al. first compared the change of LSV curves of three frequently used metal catalysts (Ni, Co, and Fe) tested in 1 M
1Joule,
Cell Press, 5/F Unit A, Digital China Centre, No. 567 Tianshan West Road, Changning District, Shanghai 200335, China *Correspondence: [email protected] https://doi.org/10.1016/j.joule.2019.05.024
conclusion drawn from this research can help to screen more optimized catalysts by calculating the adsorbing and bonding energy to OH*.
Figure 1. Illustration of Fishing the Oxygen Intermediates with Alcohol Molecules
KOH media and one that adds methanol.5 They found the different behaviors of LSV current changes for Ni, Co, and Fe after adding methanol. The left shift of LSV curves is observed and is claimed to be caused by the methanol oxidation reaction (MOR). Using DFT calculation, they found the bonding strength of OH* for Ni, Co, and Fe goes in the order of Ni > Co > Fe, which is identical to their MOR activity, while the OER activity for them varies in Co > Ni > Fe as the MOR activity competes with OER. Fe-based catalysts are claimed to not be able to adsorb the OH*, leading to its low activity for both the MOR and OER. Therefore, a trade-off is proposed that a suitable bonding energy and adsorption of OH* are required for a high MOR activity. This proposal is further demonstrated with metal oxides examples. Tao et al. found that the surface coverage behavior of OH* varies as NiO > Co3O4 > IrO2 as it goes for the MOR activity, while the OER activity is confirmed to go the opposite way.5 Taking the state-of-the-art OER catalyst IrO2 as an example, Tao et al. explored the mechanism in acidic media.5 They
found that in acid media, the OH* reaction with alcohol molecules is more preferred as the competition of MOR to OER is less. Finally, using this theory, a demonstration of OER catalyst optimization is presented. As is well known, neither Ni nor Fe exhibits high OER activity while their combination displays a positive effect. This is explained as the adsorption and bonding of OH* is optimized in the hybrid NiFe-based catalyst. An example is given of the NiFe(oxy)hydroxide: adding Fe contents into Ni catalysts can significantly lower the binding energy of OH* and mediate the quantity of OH* adsorbed on the catalyst surface; thus, a better OER activity is obtained, which is further demonstration of their proposed strategy. This research innovatively proposed an operando capture of oxygen intermediates to study the oxygen-involved catalytic processes (Figure 1). It provides a unique method to guide the catalyst design for OER, which is a key reaction for proton exchange membrane water electrolysis, hydrogen produced from water splitting, and metal air battery applications, etc. The
While this research is based on vast investigation of literature and massive electrochemical and spectroscopic characterization data, several questions remain as to (1) how to 100% preclude the other possible reactions that contribute to the MOR process (for instance, metal redox reactions), (2) how to further increase the accuracy/ sensitivity to the intermediates so that OH* does not have to reach a certain concentration to be detected, (3) whether there is a way to tell the reaction process more direct than conducting an LSV test, and (4) how to probe other oxygen intermediates.
1. Roth, C., Benker, N., Buhrmester, T., Mazurek, M., Loster, M., Fuess, H., Koningsberger, D.C., and Ramaker, D.E. (2005). Determination of O[H] and CO coverage and adsorption sites on PtRu electrodes in an operating PEM fuel cell. J. Am. Chem. Soc. 127, 14607–14615. 2. Shao, M.H., and Adzic, R.R. (2005). Spectroscopic identification of the reaction intermediates in oxygen reduction on gold in alkaline solutions. J. Phys. Chem. B 109, 16563–16566. 3. Nayak, S., McPherson, I.J., and Vincent, K.A. (2018). Adsorbed intermediates in oxygen reduction on platinum nanoparticles observed by in situ IR spectroscopy. Angew. Chem. Int. Ed. 57, 12855–12858. 4. Hunter, B.M., Thompson, N.B., Mu¨ller, A.M., Rossman, G.R., Hill, M.G., Winkler, J.R., and Gray, H.B. (2018). Trapping an iron (VI) watersplitting intermediate in nonaqueous media. Joule 2, 747–763. 5. Tao, H.B., Xu, Y., Huang, X., Chen, J., Pei, L., Zhang, J., Chen, J., and Liu, B. (2019). A general method to probe oxygen evolution intermediates at operating conditions. Joule 3, this issue, 1498–1509. 6. Rodriguez, P., Kwon, Y., and Koper, M.T.M. (2011). The promoting effect of adsorbed carbon monoxide on the oxidation of alcohols on a gold catalyst. Nat. Chem. 4, 177–182. 7. Kwon, Y., Lai, S.C.S., Rodriguez, P., and Koper, M.T.M. (2011). Electrocatalytic oxidation of alcohols on gold in alkaline media: base or gold catalysis? J. Am. Chem. Soc. 133, 6914–6917.
Joule 3, 1404–1414, June 19, 2019 1409
5. Bui, M., Adjiman, C.S., Bardow, A., Anthony, E.J., Boston, A., Brown, S., Fennell, P.S., Fuss, S., Galindo, A., Hackett, L.A., et al. (2018). Carbon Capture and Storage (CCS): the way forward. Energy Environ. Sci. 11, 1062–1176. 6. Davis, S.J., Lewis, N.S., Shaner, M., Aggarwal, S., Arent, D., Azevedo, I.L., Benson, S.M., Bradley, T., Brouwer, J., Chiang, Y.-M., et al. (2018). Net-zero emissions energy systems. Science 360, eaas9793. 7. 14th International Conference on Greenhouse Gas Control Technologies (GHGT 14). 21–26 October 2018. Melbourne, Australia.
8. Jacobson, M.Z., Delucchi, M.A., Cameron, M.A., and Frew, B.A. (2015). Low-cost solution to the grid reliability problem with 100% penetration of intermittent wind, water, and solar for all purposes. Proc. Natl. Acad. Sci. USA 112, 15060–15065. 9. Clack, C.T.M., Qvist, S.A., Apt, J., Bazilian, M., Brandt, A.R., Caldeira, K., Davis, S.J., Diakov, V., Handschy, M.A., Hines, P.D.H., et al. (2017). Evaluation of a proposal for reliable low-cost grid power with 100% wind, water, and solar. Proc. Natl. Acad. Sci. USA 114, 6722–6727. 10. Webb, R.. The Economics of Star Trek. https://medium.com/@RickWebb/theeconomics-of-star-trek-29bab88d50.
Preview
Fish the Oxygen Intermediates Rose Changrong Zhu1,* Figuring out the oxygen intermediates in the oxygen evolution reaction (OER) process is vital to its full understanding. Efficient and prompt capture of oxygen intermediates has been a challenging research topic. In this issue of Joule, Bin Liu, Jingguang Chen, and colleagues developed an operando technique to probe the OH*, the first intermediate in the OER process. They found that the OH* is electrophilic. Inspired by the preferred combination of electrophiles and nucleophiles, they applied nucleophilic bait to catch the OH*. A clear sign is given by the current difference in the linear sweep voltammetry curve when alcohols such as methanol are added. This efficient in situ probing of oxygen intermediates opens a door for exploring the oxygen-involved process in energy storage and conversion research. Oxygen evolution reaction (OER) is part of various important energy conversion processes—for instance, water splitting, metal air battery, methanol oxidation, etc. Electrocatalysis of water oxidation is a dominating way to obtain hydrogen fuel, while OER is the more sluggish reaction in this process, contributing to a majority of the overpotential needed to drive the reaction. Knowing the exact reaction steps, particularly the rate-determining step, can help advise the catalyst design, which should be the most efficient way to reduce the overpotential of OER. Undoubtedly, oxygen intermediates are the most important information in understanding the OER mechanisms. Therefore, plenty of efforts are spent
on detecting the oxygen intermediates in OER fundamental research. It is noteable that early research has been focused on using spectroscopic techniques for in situ probing. Fourteen years ago, X-ray absorption measurements during fuel cell operation provided the first clue of the O[H] and CO coverage and adsorption sites on PtRu electrodes.1 Meanwhile, surfaceenhanced infrared reflection-absorption spectroscopy with an attenuated total reflection configuration was used to identify the intermediates of the oxygen reduction reaction (ORR) on gold electrodes.2 Continuously, in situ infrared spectroscopy is applied to probe the surface chemistry of a commercial carbon-supported Pt nanopar-
1408 Joule 3, 1404–1414, June 19, 2019 ª 2019 Published by Elsevier Inc.
ticle catalyst during oxygen reduction. The IR spectra show potential-dependent appearance of adsorbed superoxide and hydroperoxide intermediates on Pt.3 Not limited in noble metal, recent research caught the Fe(VI) in nonaqueous solution during water oxidation process utilizing the in situ infrared, UV-visible, Raman, luminescence, and Mo¨ssbauer spectroelectrochemistry techniques.4 However, those spectroscopic techniques need a high vacuum environment and other special conditions, making it less approachable. In addition, they are less efficient for studying aqueous media. Unlike previous research, Tao et al.5 propose an electrochemical way to study the OER reaction process. Their work is inspired by the unique phenomena that carbon monoxide (electrophilic) irreversibly adsorbed on an Au(111) surface acts as a promoter for the electrocatalytic oxidation of methanol6 and the deprotonation process of alcohols in the alkali solutions.7 Tao et al. first compared the change of LSV curves of three frequently used metal catalysts (Ni, Co, and Fe) tested in 1 M
1Joule,
Cell Press, 5/F Unit A, Digital China Centre, No. 567 Tianshan West Road, Changning District, Shanghai 200335, China *Correspondence: [email protected] https://doi.org/10.1016/j.joule.2019.05.024
conclusion drawn from this research can help to screen more optimized catalysts by calculating the adsorbing and bonding energy to OH*.
Figure 1. Illustration of Fishing the Oxygen Intermediates with Alcohol Molecules
KOH media and one that adds methanol.5 They found the different behaviors of LSV current changes for Ni, Co, and Fe after adding methanol. The left shift of LSV curves is observed and is claimed to be caused by the methanol oxidation reaction (MOR). Using DFT calculation, they found the bonding strength of OH* for Ni, Co, and Fe goes in the order of Ni > Co > Fe, which is identical to their MOR activity, while the OER activity for them varies in Co > Ni > Fe as the MOR activity competes with OER. Fe-based catalysts are claimed to not be able to adsorb the OH*, leading to its low activity for both the MOR and OER. Therefore, a trade-off is proposed that a suitable bonding energy and adsorption of OH* are required for a high MOR activity. This proposal is further demonstrated with metal oxides examples. Tao et al. found that the surface coverage behavior of OH* varies as NiO > Co3O4 > IrO2 as it goes for the MOR activity, while the OER activity is confirmed to go the opposite way.5 Taking the state-of-the-art OER catalyst IrO2 as an example, Tao et al. explored the mechanism in acidic media.5 They
found that in acid media, the OH* reaction with alcohol molecules is more preferred as the competition of MOR to OER is less. Finally, using this theory, a demonstration of OER catalyst optimization is presented. As is well known, neither Ni nor Fe exhibits high OER activity while their combination displays a positive effect. This is explained as the adsorption and bonding of OH* is optimized in the hybrid NiFe-based catalyst. An example is given of the NiFe(oxy)hydroxide: adding Fe contents into Ni catalysts can significantly lower the binding energy of OH* and mediate the quantity of OH* adsorbed on the catalyst surface; thus, a better OER activity is obtained, which is further demonstration of their proposed strategy. This research innovatively proposed an operando capture of oxygen intermediates to study the oxygen-involved catalytic processes (Figure 1). It provides a unique method to guide the catalyst design for OER, which is a key reaction for proton exchange membrane water electrolysis, hydrogen produced from water splitting, and metal air battery applications, etc. The
While this research is based on vast investigation of literature and massive electrochemical and spectroscopic characterization data, several questions remain as to (1) how to 100% preclude the other possible reactions that contribute to the MOR process (for instance, metal redox reactions), (2) how to further increase the accuracy/ sensitivity to the intermediates so that OH* does not have to reach a certain concentration to be detected, (3) whether there is a way to tell the reaction process more direct than conducting an LSV test, and (4) how to probe other oxygen intermediates.
1. Roth, C., Benker, N., Buhrmester, T., Mazurek, M., Loster, M., Fuess, H., Koningsberger, D.C., and Ramaker, D.E. (2005). Determination of O[H] and CO coverage and adsorption sites on PtRu electrodes in an operating PEM fuel cell. J. Am. Chem. Soc. 127, 14607–14615. 2. Shao, M.H., and Adzic, R.R. (2005). Spectroscopic identification of the reaction intermediates in oxygen reduction on gold in alkaline solutions. J. Phys. Chem. B 109, 16563–16566. 3. Nayak, S., McPherson, I.J., and Vincent, K.A. (2018). Adsorbed intermediates in oxygen reduction on platinum nanoparticles observed by in situ IR spectroscopy. Angew. Chem. Int. Ed. 57, 12855–12858. 4. Hunter, B.M., Thompson, N.B., Mu¨ller, A.M., Rossman, G.R., Hill, M.G., Winkler, J.R., and Gray, H.B. (2018). Trapping an iron (VI) watersplitting intermediate in nonaqueous media. Joule 2, 747–763. 5. Tao, H.B., Xu, Y., Huang, X., Chen, J., Pei, L., Zhang, J., Chen, J., and Liu, B. (2019). A general method to probe oxygen evolution intermediates at operating conditions. Joule 3, this issue, 1498–1509. 6. Rodriguez, P., Kwon, Y., and Koper, M.T.M. (2011). The promoting effect of adsorbed carbon monoxide on the oxidation of alcohols on a gold catalyst. Nat. Chem. 4, 177–182. 7. Kwon, Y., Lai, S.C.S., Rodriguez, P., and Koper, M.T.M. (2011). Electrocatalytic oxidation of alcohols on gold in alkaline media: base or gold catalysis? J. Am. Chem. Soc. 133, 6914–6917.
Joule 3, 1404–1414, June 19, 2019 1409