Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Article
  • Published:

Tuning water reduction through controlled nanoconfinement within an organic liquid matrix

Nature Catalysis volume 3, pages 656–663 (2020)Cite this article

Subjects

Abstract

The growing hydrogen economy requires accelerating the hydrogen evolution reaction. The water dissociation step (Volmer step) has been proposed as a main kinetic limitation, but the mechanisms at play in the electrochemical double-layer are poorly understood. This is due to the dual role of water: it acts both as a reactant and as a solvent. Here we propose to confine water inside an organic liquid matrix in order to isolate the sole role of water as a reactant. We observed the formation of aqueous-rich nanodomains, whose size can be tuned by changing the supporting electrolyte and found that the reactivity of the system varies significantly with its nanostructure. Depending on the conditions, the reactivity is dominated by either the strength of short-range cation–water interactions or the formation of long chains of water molecules. Understanding this paves the way towards the development of more efficient and selective electrocatalysts for water, CO2, O2 or N2 reduction.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: Chemical strategy to select long-range and short-range interactions.
Fig. 2: Modification of the reactivity of water depending on its environment.
Fig. 3: Water structure in the vicinity of hydrophobic TBA+ cation.
Fig. 4: Formation of Li+–H2O nanoscale reactors.
Fig. 5: Formation of nanochannels to enhance the water reduction.

Similar content being viewed by others

Data availability

Molecular dynamics inputs, initial and final configurations are available on a ChemRxiv depository (https://doi.org/10.26434/chemrxiv.11926293). Other experimental raw data or computational data are available from the corresponding authors on reasonable request.

Code availability

The Metalwalls code is available online at https://gitlab.com/ampere2/metalwalls. The analysis code used to obtain the structure factor is available online at https://gitlab.com/salanne/structure-factors.

References

  1. The Future of Hydrogen (IEA, 2019).

  2. Kibsgaard, J. & Chorkendorff, I. Considerations for the scaling-up of water splitting catalysts. Nat. Energy 4, 430–433 (2019).

    Article  Google Scholar 

  3. Zheng, Y., Jiao, Y., Jaroniec, M. & Qiao, S. Z. Advancing the electrochemistry of the hydrogen-evolution reaction through combining experiment and theory. Angew. Chem. Int. Ed. 54, 52–65 (2015).

    Article  CAS  Google Scholar 

  4. Zheng, Y., Jiao, Y., Vasileff, A. & Qiao, S.-Z. The hydrogen evolution reaction in alkaline solution: from theory, single crystal models, to practical electrocatalysts. Angew. Chem. Int. Ed. 57, 7568–7579 (2018).

    Article  CAS  Google Scholar 

  5. Subbaraman, R. et al. Enhancing hydrogen evolution activity in water splitting by tailoring Li+-Ni(OH)2-Pt Interfaces. Science 334, 1256–1260 (2011).

    Article  CAS  PubMed  Google Scholar 

  6. Hu, C., Zhang, L. & Gong, J. Recent progress made in the mechanism comprehension and design of electrocatalysts for alkaline water splitting. Energy Environ. Sci. 12, 2620–2645 (2019).

    Article  CAS  Google Scholar 

  7. Trasatti, S. Work function, electronegativity, and electrochemical behaviour of metals. J. Electroanal. Chem. Interfacial Electrochem 39, 163–184 (1972).

    Article  CAS  Google Scholar 

  8. Nørskov, J. K. et al. Trends in the exchange current for hydrogen evolution. J. Electrochem. Soc. 152, J23–J26 (2005).

    Article  CAS  Google Scholar 

  9. Sheng, W. et al. Correlating hydrogen oxidation and evolution activity on platinum at different pH with measured hydrogen binding energy. Nat. Commun. 6, 5848 (2015).

    Article  CAS  PubMed  Google Scholar 

  10. Zheng, J., Sheng, W., Zhuang, Z., Xu, B. & Yan, Y. Universal dependence of hydrogen oxidation and evolution reaction activity of platinum-group metals on pH and hydrogen binding energy. Sci. Adv. 2, e1501602 (2016).

    Article  PubMed  PubMed Central  CAS  Google Scholar 

  11. Chen, X., McCrum, I. T., Schwarz, K. A., Janik, M. J. & Koper, M. T. M. Co-adsorption of cations as the cause of the apparent ph dependence of hydrogen adsorption on a stepped platinum single-crystal electrode. Angew. Chem. Int. Ed. 56, 15025–15029 (2017).

    Article  CAS  Google Scholar 

  12. Janik, M. J., McCrum, I. T. & Koper, M. T. M. On the presence of surface bound hydroxyl species on polycrystalline Pt electrodes in the “hydrogen potential region” (0–0.4 V-RHE). J. Catal. 367, 332–337 (2018).

    Article  CAS  Google Scholar 

  13. Dubouis, N. & Grimaud, A. The hydrogen evolution reaction: from material to interfacial descriptors. Chem. Sci. 10, 9165–9181 (2019).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  14. Zeradjanin, A. R. et al. What is the trigger for the hydrogen evolution reaction? – towards electrocatalysis beyond the Sabatier principle. Phys. Chem. Chem. Phys. 22, 8768–8780 (2020).

    Article  CAS  PubMed  Google Scholar 

  15. Velasco-Velez, J.-J. et al. The structure of interfacial water on gold electrodes studied by x-ray absorption spectroscopy. Science 346, 831–834 (2014).

    Article  CAS  PubMed  Google Scholar 

  16. Wu, C. H. et al. Molecular-scale structure of electrode–electrolyte interfaces: the case of platinum in aqueous sulfuric acid. J. Am. Chem. Soc. 140, 16237–16244 (2018).

    Article  CAS  PubMed  Google Scholar 

  17. Li, C.-Y. et al. In situ probing electrified interfacial water structures at atomically flat surfaces. Nat. Mater. 18, 697–701 (2019).

    Article  CAS  PubMed  Google Scholar 

  18. Ledezma-Yanez, I. et al. Interfacial water reorganization as a pH-dependent descriptor of the hydrogen evolution rate on platinum electrodes. Nat. Energy 2, 17031 (2017).

    Article  CAS  Google Scholar 

  19. Sarabia, F. J., Sebastián-Pascual, P., Koper, M. T. M., Climent, V. & Feliu, J. M. Effect of the interfacial water structure on the hydrogen evolution reaction on Pt(111) modified with different nickel hydroxide coverages in alkaline media. ACS Appl. Mater. Interfaces 11, 613–623 (2019).

    Article  CAS  PubMed  Google Scholar 

  20. Dubouis, N. et al. The fate of water at the electrochemical interfaces: electrochemical behavior of free water versus coordinating water. J. Phys. Chem. Lett. 9, 6683–6688 (2018).

    Article  CAS  PubMed  Google Scholar 

  21. Suárez-Herrera, M. F., Costa-Figueiredo, M. & Feliu, J. M. Voltammetry of basal plane platinum electrodes in acetonitrile electrolytes: effect of the presence of water. Langmuir 28, 5286–5294 (2012).

    Article  PubMed  CAS  Google Scholar 

  22. Ledezma-Yanez, I., Díaz-Morales, O., Figueiredo, M. C. & Koper, M. T. M. Hydrogen oxidation and hydrogen evolution on a platinum electrode in acetonitrile. ChemElectroChem 2, 1612–1622 (2015).

    Article  CAS  Google Scholar 

  23. Ledezma-Yanez, I. & Koper, M. T. M. Influence of water on the hydrogen evolution reaction on a gold electrode in acetonitrile solution. J. Electroanal. Chem. 793, 18–24 (2017).

    Article  CAS  Google Scholar 

  24. Cassone, G., Creazzo, F., Giaquinta, P. V., Sponer, J. & Saija, F. Ionic diffusion and proton transfer in aqueous solutions of alkali metal salts. Phys. Chem. Chem. Phys. 19, 20420–20429 (2017).

    Article  CAS  PubMed  Google Scholar 

  25. Thordarson, P. Determining association constants from titration experiments in supramolecular chemistry. Chem. Soc. Rev. 40, 1305–1323 (2011).

    Article  CAS  PubMed  Google Scholar 

  26. Marx, D., Tuckerman, M. E., Hutter, J. & Parrinello, M. The nature of the hydrated excess proton in water. Nature 397, 601–604 (1999).

    Article  CAS  Google Scholar 

  27. Tuckerman, M. E., Marx, D. & Parrinello, M. The nature and transport mechanism of hydrated hydroxide ions in aqueous solution. Nature 417, 925–929 (2002).

    Article  CAS  PubMed  Google Scholar 

  28. Geissler, P. L. Autoionization in liquid water. Science 291, 2121–2124 (2001).

    Article  CAS  PubMed  Google Scholar 

  29. Filhol, J.-S. & Neurock, M. Elucidation of the electrochemical activation of water over Pd by first principles. Angew. Chem. Int. Ed. 45, 402–406 (2006).

    Article  CAS  Google Scholar 

  30. Lange, K. M., Hodeck, K. F., Schade, U. & Aziz, E. F. Nature of the hydrogen bond of water in solvents of different polarities. J. Phys. Chem. B 114, 16997–17001 (2010).

    Article  CAS  PubMed  Google Scholar 

  31. Lange, K. M. et al. On the origin of the hydrogen-bond-network nature of water: X-ray absorption and emission spectra of water-acetonitrile mixtures. Angew. Chem. Int. Ed. 50, 10621–10625 (2011).

    Article  CAS  Google Scholar 

  32. Huang, Y., Nielsen, R. J., Goddard, W. A. & Soriaga, M. P. The reaction mechanism with free energy barriers for electrochemical dihydrogen evolution on MoS2. J. Am. Chem. Soc. 137, 6692–6698 (2015).

    Article  CAS  PubMed  Google Scholar 

  33. Nishikawa, K., Kasahara, Y. & Ichioka, T. Inhomogeneity of mixing in acetonitrile aqueous solution studied by small-angle X-ray scattering. J. Phys. Chem. B 106, 693–700 (2002).

    Article  CAS  Google Scholar 

  34. Takamuku, T. et al. Large-angle X-ray scattering and small-angle neutron scattering study on phase separation of acetonitrile−water mixtures by addition of NaCl. J. Phys. Chem. B 105, 6236–6245 (2001).

    Article  CAS  Google Scholar 

  35. Huang, N. et al. X-ray Raman scattering provides evidence for interfacial acetonitrile–water dipole interactions in aqueous solutions. J. Chem. Phys. 135, 164509 (2011).

    Article  PubMed  PubMed Central  CAS  Google Scholar 

  36. Brehm, M., Weber, H., Thomas, M., Hollóczki, O. & Kirchner, B. Domain analysis in nanostructured liquids: a post-molecular dynamics study at the example of ionic liquids. ChemPhysChem 16, 3271–3277 (2015).

    Article  CAS  PubMed  Google Scholar 

  37. Liu, E. et al. Unifying the hydrogen evolution and oxidation reactions kinetics in base by identifying the catalytic roles of hydroxyl–water–cation adducts. J. Am. Chem. Soc. 141, 3232–3239 (2019).

    Article  CAS  PubMed  Google Scholar 

  38. Chen, M. et al. Hydroxide diffuses slower than hydronium in water because its solvated structure inhibits correlated proton transfer. Nat. Chem. 10, 413–419 (2018).

    Article  PubMed  CAS  Google Scholar 

  39. Hollóczki, O., Macchieraldo, R., Gleede, B., Waldvogel, S. R. & Kirchner, B. Interfacial domain formation enhances electrochemical synthesis. J. Phys. Chem. Lett. 10, 1192–1197 (2019).

    Article  PubMed  CAS  Google Scholar 

  40. Meng, Y., Aldous, L., Belding, S. R. & Compton, R. G. The hydrogen evolution reaction in a room temperature ionic liquid: mechanism and electrocatalyst trends. Phys. Chem. Chem. Phys. 14, 5222–5228 (2012).

    Article  CAS  PubMed  Google Scholar 

  41. Bi, S. et al. Minimizing the electrosorption of water from humid ionic liquids on electrodes. Nat. Commun. 9, 5222 (2018).

    Article  PubMed  PubMed Central  CAS  Google Scholar 

  42. Feng, G., Jiang, X., Qiao, R. & Kornyshev, A. A. Water in ionic liquids at electrified interfaces: the anatomy of electrosorption. ACS Nano 8, 11685–11694 (2014).

    Article  CAS  PubMed  Google Scholar 

  43. Suo, L. et al. “Water-in-salt” electrolyte enables high-voltage aqueous lithium-ion chemistries. Science 350, 938–943 (2015).

    Article  CAS  PubMed  Google Scholar 

  44. Yamada, Y. et al. Hydrate-melt electrolytes for high-energy-density aqueous batteries. Nat. Energy 1, 16129 (2016).

    Article  CAS  Google Scholar 

  45. Borodin, O. et al. Liquid structure with nano-heterogeneity promotes cationic transport in concentrated electrolytes. ACS Nano 11, 10462–10471 (2017).

    Article  CAS  PubMed  Google Scholar 

  46. Dubouis, N. et al. The role of the hydrogen evolution reaction in the solid–electrolyte interphase formation mechanism for “Water-in-Salt” electrolytes. Energy Environ. Sci. 11, 3491–3499 (2018).

    Article  CAS  Google Scholar 

  47. McEldrew, M., Goodwin, Z. A. H., Kornyshev, A. A. & Bazant, M. Z. Theory of the double layer in water-in-salt electrolytes. J. Phys. Chem. Lett. 9, 5840–5846 (2018).

    Article  CAS  PubMed  Google Scholar 

  48. Birdja, Y. Y. et al. Advances and challenges in understanding the electrocatalytic conversion of carbon dioxide to fuels. Nat. Energy 4, 732–745 (2019).

    Article  CAS  Google Scholar 

  49. Andersen, S. Z. et al. A rigorous electrochemical ammonia synthesis protocol with quantitative isotope measurements. Nature 570, 504–508 (2019).

    Article  CAS  PubMed  Google Scholar 

  50. Tanner, J. E. Use of the stimulated Echo in NMR diffusion studies. J. Chem. Phys. 52, 2523–2526 (1970).

    Article  CAS  Google Scholar 

  51. Abraham, M. J. et al. GROMACS: High performance molecular simulations through multi-level parallelism from laptops to supercomputers. SoftwareX 1–2, 19–25 (2015).

    Article  Google Scholar 

  52. Grabuleda, X., Jaime, C. & Kollman, P. A. Molecular dynamics simulation studies of liquid acetonitrile: New six-site model. J. Comput. Chem. 21, 901–908 (2000).

    Article  CAS  Google Scholar 

  53. Berendsen, H. J. C., Grigera, J. R. & Straatsma, T. P. The missing term in effective pair potentials. J. Phys. Chem. 91, 6269–6271 (1987).

    Article  CAS  Google Scholar 

  54. Liu, X. et al. New force field for molecular simulation of guanidinium-based ionic liquids. J. Phys. Chem. B 110, 12062–12071 (2006).

    Article  CAS  PubMed  Google Scholar 

  55. Bhowmik, D. et al. Aqueous solutions of tetraalkylammonium halides: ion hydration, dynamics and ion–ion interactions in light of steric effects. Phys. Chem. Chem. Phys. 16, 13447–13457 (2014).

    Article  CAS  PubMed  Google Scholar 

  56. Ȧqvist, J. Ion-water interaction potentials derived from free energy perturbation simulations. J. Phys. Chem. 94, 8021–8024 (1990).

    Article  Google Scholar 

  57. Nosé, S. A unified formulation of the constant temperature molecular dynamics methods. J. Chem. Phys. 81, 511–519 (1984).

    Article  Google Scholar 

  58. Evans, D. J. & Holian, B. L. The Nose–Hoover thermostat. J. Chem. Phys. 83, 4069–4074 (1985).

    Article  CAS  Google Scholar 

  59. Martínez, L., Andrade, R., Birgin, E. G. & Martínez, J. M. PACKMOL: A package for building initial configurations for molecular dynamics simulations. J. Comput. Chem. 30, 2157–2164 (2009).

    Article  PubMed  CAS  Google Scholar 

  60. Essmann, U. et al. A smooth particle mesh Ewald method. J. Chem. Phys. 103, 8577–8593 (1995).

    Article  CAS  Google Scholar 

  61. Hess, B., Bekker, H., Berendsen, H. J. C. & Fraaije, J. G. E. M. LINCS: A linear constraint solver for molecular simulations. J. Comput. Chem. 18, 1463–1472 (1997).

    Article  CAS  Google Scholar 

  62. Brehm, M. & Kirchner, B. TRAVIS - A free analyzer and visualizer for Monte Carlo and molecular dynamics trajectories. J. Chem. Inf. Model. 51, 2007–2023 (2011).

    Article  CAS  PubMed  Google Scholar 

  63. Humphrey, W., Dalke, A. & Schulten, K. VMD: Visual molecular dynamics. J. Mol. Graph. 14, 33–38 (1996).

    Article  CAS  PubMed  Google Scholar 

  64. Marin-Laflèche, A. et al. MetalWalls: A classical molecular dynamics software dedicated to the simulation of electrochemical systems. Preprint at https://doi.org/10.26434/chemrxiv.12389777.v1 (2020)

  65. Reed, S. K., Lanning, O. J. & Madden, P. A. Electrochemical interface between an ionic liquid and a model metallic electrode. J. Chem. Phys. 126, 084704 (2007).

    Article  PubMed  CAS  Google Scholar 

  66. Siepmann, J. I. & Sprik, M. Influence of surface topology and electrostatic potential on water/electrode systems. J. Chem. Phys. 102, 511–524 (1995).

    Article  CAS  Google Scholar 

  67. Werder, T., Walther, J. H., Jaffe, R. L., Halicioglu, T. & Koumoutsakos, P. On the water−carbon interaction for use in molecular dynamics simulations of graphite and carbon nanotubes. J. Phys. Chem. B 107, 1345–1352 (2003).

    Article  CAS  Google Scholar 

  68. Gingrich, T. R. & Wilson, M. On the Ewald summation of Gaussian charges for the simulation of metallic surfaces. Chem. Phys. Lett. 500, 178–183 (2010).

    Article  CAS  Google Scholar 

  69. Ryckaert, J.-P., Ciccotti, G. & Berendsen, H. J. C. Numerical integration of the cartesian equations of motion of a system with constraints: molecular dynamics of n-alkanes. J. Comput. Phys. 23, 327–341 (1977).

    Article  CAS  Google Scholar 

  70. Ciccotti, G., Ferrario, M. & Ryckaert, J.-P. Molecular dynamics of rigid systems in cartesian coordinates a general formulation. Mol. Phys. 47, 1253–1264 (1982).

    Article  CAS  Google Scholar 

Download references

Acknowledgements

N.D. acknowledges the École Normale Supérieure for his PhD scholarship. We acknowledge the French National Research Agency for its support through the Labex STORE-EX project (ANR-10LABX-76-01). This project has received funding from the European Research Council under the European Union’s Horizon 2020 research and innovation programme (Grant No. 771294). We acknowledge SOLEIL for provision of synchrotron radiation facilities and we would like to thank Thomas Bizien for assistance in using beamline SWING.

Author information

Authors and Affiliations

  1. Chimie du Solide et de l’Énergie, Collège de France, Paris, France

    Nicolas Dubouis & Alexis Grimaud

  2. Sorbonne Université, Paris, France

    Nicolas Dubouis & Alexis Grimaud

  3. Réseau sur le Stockage Électrochimique de l’Énergie (RS2E), Amiens, France

    Nicolas Dubouis, Alessandra Serva, Roxanne Berthin, Guillaume Jeanmairet, Benjamin Porcheron, Elodie Salager, Mathieu Salanne & Alexis Grimaud

  4. Sorbonne Université, CNRS, Physico-Chimie des Électrolytes et Nanosystèmes Interfaciaux, Paris, France

    Alessandra Serva, Roxanne Berthin, Guillaume Jeanmairet & Mathieu Salanne

  5. CNRS-CEMHTI, Université d’Orléans, Orléans, France

    Benjamin Porcheron & Elodie Salager

Authors
  1. Nicolas Dubouis
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Alessandra Serva
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Roxanne Berthin
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Guillaume Jeanmairet
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Benjamin Porcheron
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Elodie Salager
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. Mathieu Salanne
    View author publications

    You can also search for this author in PubMed Google Scholar

  8. Alexis Grimaud
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

N.D. and A.G. designed the experiments. N.D. prepared and characterized the electrolytes. N.D. realized the electrochemical measurements and analysed them with A.G. The NMR characterization of the electrolytes was carried out by N.D., with further analysis by E.S. Diffusion NMR experiments were performed and analysed by B.P. and E.S. MD simulations of the electrolytes were performed by N.D., A.S., R.B. and G.J. and they were analysed and designed with M.S. All the authors edited the manuscript and discussed the scientific results.

Corresponding authors

Correspondence to Mathieu Salanne or Alexis Grimaud.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data

Extended Data Fig. 1 Water reactivity using LiTFSI as a supporting salt.

Linear sweep voltammograms recorded in acetonitrile in presence of 100 mM LiTFSI with different water contents (1, 2.5, 5, 7.5 and 10% from light to dark blue) using a rotating disc (1,600 rpm) Pt electrode with a 50 mV s−1 sweeping rate. No modification of the onset potential at which water is reduced was observed, independently of the water content, confirming that the trend previously measured for LiClO4 is independent on the nature of the anion.

Extended Data Fig. 2 Comparison of Li+-H2O and H2O-H2O interactions.

Potential of mean force between Li+ cations and Owater (a) and between Owater and Hwater (b) derived from the g(r) functions. 𝑝𝑚𝑓(𝑟)=−𝑘𝐵𝑇 ln𝑔(𝑟), where 𝑘𝐵 is the Boltzmann constant and 𝑇 the temperature (300K) for different water contents (1% in light blue, 5% in blue and 10% in dark blue). Since the largest values are obtained for Li-Owater, independently on the water content, this indicates that it is more difficult to separate one Li+ cation from a water molecule than a water molecule from another one.

Extended Data Fig. 3 Comparison of the Li+ and Na+ solvation shell.

Coordination number between Li+ cation (blue) or Na+ cations (pink) and oxygen atoms from ClO4− anions (a), nitrogen atoms from acetonitrile molecules (b) and oxygen atoms from water molecules (c) in the presence of 100 mM of AClO4 in acetonitrile containing 10% of water in mass. The simulation box for NaClO4 was similar to the LiClO4 one (Supplementary Table 1) and the Lennard-Jones parameters for Na+ were chosen from Åqvist56. The number of water molecules and ClO4- anions present in the first solvation shell of the Na+ and Li+ cations is similar, while more acetonitrile is found in the case of Na+.

Extended Data Fig. 4 Comparison of Li+-H2O and Na+-H2O interactions.

Potential of mean force between Li+ or Na+ cations and Owater (derived from the g(r) functions (pmf(𝑟)=−𝑘𝐵𝑇 ln𝑔(𝑟), where 𝑘𝐵 is the Boltzmann constant and 𝑇 the temperature (300K)) in acetonitrile containing 10% of water in mass and 100 mM of LiClO4 or NaClO4 salt. Since a smaller value is predicted in the presence of Na+ cations, this indicates that the water-Na+ interaction is weaker when compared to the water-Li+ interaction.

Extended Data Fig. 5 Evolution of the Li+ solvation shell with the salt concentration.

Coordination number between Li+ cations and nitrogen atoms from acetonitrile molecules (a) and oxygen atoms from ClO4- anions (b) and oxygen atoms from water molecules (c) in acetonitrile containing 10% of water in mass at different H2O/Li ratio (44 yellow, 8.8 orange, 4.4 red). The increase of the LiClO4 concentration results in an increased amplitude of the first plateau of the Li-O(ClO4-) coordination number, which suggests more ion-pairing, accompanied by a small increase of the acetonitrile in the first solvation shell of Li+ cations and a small decrease of the water content in the first solvation shell.

Extended Data Fig. 6 Impact of the LiClO4 concentrations on the formation of ion pairs.

a, Evolution of the electrolyte (acetonitrile with 10% of water in mass) conductivity and b, 7Li chemical shift with the LiClO4 concentration. The indicated concentrations correspond to the electrolytes previously studied with different Li/H2O ratios (Supplementary Table 3). The bell shape for the conductivity and the downfield of the 7Li suggest that ion-pairs are formed when the salt concentration is increased. The lines are guides for the eyes.

Extended Data Fig. 7 Oxygen-oxygen-pairs contribution to the X-ray weighed structure factor.

X-Ray weighted contributions from the oxygen-oxygen pairs to the global X-ray-weighted structure factor obtained from the MD simulations for acetonitrile electrolytes containing 10% of water in mass at different H2O/Li ratio (44 yellow, 8.8 orange, 4.4 red).

Extended Data Fig. 8 Impact of the concomitant increase of water and salt on the water reactivity and electrolyte structure.

a, Linear sweep voltammograms recorded in acetonitrile with a H2O/Li+ ratio of 4.4 at different water concentration (from 1% light grey, to 10% red) on a rotating disc (1,600 rpm) Pt electrode with a 50 mV s-1 sweeping rate. b, Number of LiClO4-H2O domains and their average volume depending on the LiClO4/H2O ratio at 10% of water concentration extracted from the MD simulations. c, SAXS intensity in the low-q range of acetonitrile for the electrolytes with 1% (grey), 5% (rose) or 10% of added H2O at constant H2O/Li+ ratio of 4.4 and d, corresponding coordination numbers between the Li+ cations and acetonitrile molecules, ClO4- anions and water molecules. The simulation box for the 5% H2O electrolyte contains 966 acetonitrile molecules, 110 water molecules and 25 LiClO4 ion pairs with a box length of 44.32 Å. Since the H2O/Li ratio is not modified in this set of experiments, a similar short-range environment for the Li+ cations is maintained in this third series of electrolytes. The linear-sweep voltammograms recorded with this series of electrolytes show a gradual reduction of the electrode passivation and a gradual shift of the onset potential for reduction toward less negative values when the concentration is increased. Logically, this behavior directly results from a combination of the two extreme trends previously measured (Figs. 2 and 5 in the main text). Furthermore, a significant increase in the SAXS intensity at low-q with the Li-H2O concentrations is observed, experimentally confirming the growth of these long-range LiClO4-H2O domains in this third series of electrolytes. These observations confirm the impact of the long-range organization of the water-rich nanodomains on the water reduction potential.

Extended Data Fig. 9 Comparison of the water reduction on gold and platinum electrodes.

a, Linear sweep voltammograms recorded over a platinum electrode in acetonitrile with TBAClO4 (left panel) at 100 mM with 1% (grey) or 10% (dark blue) in mass of water and with LiClO4 (right panel) at 100 mM with 1% of water (grey) or 10% of water (dark blue) or 2M LiClO4 with 10% of water (brown). b, Exchange current densities for the HER over platinum and gold electrodes compared with the computed free energy for the formation of the adsorbed hydrogen intermediate (Data taken from Nørskov, J. K. et al.8). c, Linear sweep voltammograms recorded over a gold electrode in acetonitrile with TBAClO4 (left panel) at 100 mM with 1% (grey) or 10% (dark blue) in mass of water and with LiClO4 (right panel) at 100 mM with 1% of water (grey) or 10% of water (dark blue) or 2M LiClO4 with 10% of water (brown) The electrolyte effects (short- and long-range) are observed whatever the position of the catalyst on the Volcano plot made using the hydrogen binding energy as descriptor. Briefly, in presence of TBA cations the water can be reduced only at large water concentrations on both Au and Pt electrodes. Regarding the lithium case, increasing only the water concentration does not shift the onset potential for the water reduction on gold and platinum electrodes. Nevertheless, at high water concentration, increasing the lithium salt concentration shifts the reduction of water toward less negative potentials.

Extended Data Fig. 10 Onset potential for the water reduction as a function of the cation-water interaction or the size of the aqueous-rich domains.

a, Onset potential for the water reduction (at j = 1 mA cm-2) in acetonitrile electrolyte with 5% in mass of water and 100 mM of TBA, Na or Li perchlorate expressed in function of the activation energy for the cation-water separation obtained from the cation-Owater potential of mean force. b, Onset potential for the water reduction (at j = 1 mA cm-2) in acetonitrile electrolyte with 10% in mass of water at different Li/H2O ratios expressed in function of the aqueous domain volume obtained from the domain analysis of the molecular dynamics simulations. At the short range, the strength of the cation-water molecule interaction that can be assessed by the activation energy for the cation-water separation extracted from the cation-water potential of mean force may be considered as a potential descriptor describing the water reduction. Nevertheless, this physical parameter, which is not strongly modified when for instance the salt concentration in the electrolyte is increased, cannot capture the HER kinetics when entering a second regime where long-range parameters, such as the volume of the H2O-rich nanodomains, can be considered as a physical descriptor.

Supplementary information

Supplementary Information

Supplementary Methods, Figs. 1–9 and Tables 1–5.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Dubouis, N., Serva, A., Berthin, R. et al. Tuning water reduction through controlled nanoconfinement within an organic liquid matrix. Nat Catal 3, 656–663 (2020). https://doi.org/10.1038/s41929-020-0482-5

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s41929-020-0482-5

This article is cited by

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing