Skip to content

Effects of interlayer confinement and hydration on capacitive charge storage in birnessite

Summary

This entry points to a publisher galley / proof PDF (Boyd_birnessite_NatureMaterials_2021_galley.pdf) for the Nature Materials article DOI 10.1038/s41563-021-01066-4 on birnessite capacitive charge storage under interlayer confinement and hydration. The scientific account matches [[2021boyd-nat-effects-interlayer]], which uses the non-galley PDF Boyd_birnessite_NatureMaterials_2021.pdf. The study combines ex situ XRD, EQCM, in situ Raman, operando AFM dilatometry, DFT, and ReaxFF grand canonical Monte Carlo and molecular dynamics to connect interlayer spacing, mass transport, and atomistic K⁺ / H₂O pathways in nanoconfined, hydrated interlayers. Cyclic voltammetry in neutral aqueous electrolytes (e.g. 0.5 M K₂SO₄) is compared to non-aqueous conditions with bulky cations to test intercalation versus surface-only charge storage. The combined data support intercalation in hydrated interlayers that can appear capacitive because structural water mediates cation–MnO₂ interactions with limited hysteresis. Readers comparing this galley PDF to the final article should verify figure numbering, supplementary video references, and any Mn oxidation state assignments against the publisher proof corrections recorded in [[2021boyd-nat-effects-interlayer]].

Methods

This pdf_path is a publisher proof/galley; for Methods detail and figure numbering aligned to the final issue, read [[2021boyd-nat-effects-interlayer]] and the same DOI on the publisher site. Summaries here mirror that article at a high level.

Experiments

Electrodeposited birnessite films; CV at controlled sweep rates in aqueous electrolytes (e.g. 0.5 M K₂SO₄); 298 K class temperature; XRD ( (001) spacing vs potential ); EQCM; Raman (Mn–O); operando AFM dilatometry for out-of-plane height.

MD application (ReaxFF + intercalation sampling)

  • Engine / code: ReaxFF-based molecular dynamics and interlayer GCMC/MD for K⁺+H₂O; exact executable naming N/A—treat the VOR SI + [[2021boyd-nat-effects-interlayer]] as the canonical protocol source, not this galley pdf_path.
  • System size & composition: Birnessite-like layered MnOₓ supercells with explicit K⁺ and H₂O in the interlayer gallery; atom counts and in-plane repeats are N/A on this proof-path page—use the VOR SI for the exact stoichiometry and unit cell vectors.
  • Boundaries / periodicity: PBC in the in-plane directions of the layered simulation cell (see VOR SI for full boundary conditions and any vacuum/electrolyte padding).
  • Ensemble / thermostat / timestep / run length / interatomic cutoffs / QEq: NVT-class sampling in portions of the workflow, but N/A here: copy 0.25 fs-class timestep (if used), equilibration/production ps–ns lengths, Langevin (or other) thermostat labels, and any NPT vs NVT choices from the VOR pdf_path/SI rather than the proof file.

Static DFT in this work

  • N/A for full detail on this page—interlayer K⁺+H₂O DFT in the same study is summarized on [[2021boyd-nat-effects-interlayer]].

Findings

The main text supports (near-)ideal pseudocapacitive CV shapes together with large gravimetric capacitance and (001) XRD moves and EQCM signatures of H₂O+K co-transport in a confined interlayer—a pseudocapacitor-like look from cyclic kinetics. ReaxFF+sampling supports H₂O+K⁺ uptake (supplementary videos on the VOR) compared with a simple K⁺-only exchange story. For citable numbers and figure labels, avoid the proof pdf_path for primary evidence—use the version-of-record and [[2021boyd-nat-effects-interlayer]].

Limitations

Proof/galley files can differ from the final Nature Materials layout. Thin-film morphology and electrolyte scope constrain generalization; ReaxFF simplifies Mn redox electronic structure. EQCM interpretation assumes known solvent incorporation stoichiometries; combined XRD/Raman/AFM constraints in the article are what tie mass signals to intercalation rather than adsorption-only pictures. This caveat applies equally to galley and final PDFs.

Relevance to group

Adri van Duin co-authorship; ReaxFF GCMC/MD supports intercalation mechanisms for birnessite supercapacitors.

Citations and evidence anchors

Reader notes (navigation)