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# Autoionization-driven ordering of interfacial water into an anisotropic proton conductor
## The adsorbate and its field
At a hydrophilic surface, water adsorbs into an ordered honeycomb film, a few layers thick (3–4). Autoionization between this adsorbate and the adjacent liquid releases H⁺ into the liquid and retains OH⁻ at the surface. The loss of bridging hydrogens allows adjacent layers to shift and collapse together — the layers slide so that O from one layer meets H from the next, forming new bonds as they compress. The resulting structure is the most stable phase for the deprotonated network: a thin (~1 nm) adsorbate of composition (H₃O₂⁻)ₙ, with honeycomb layers shifted by half an oxygen.
Only one carrier is mobile: H⁺ leaves, OH⁻ stays. This is the strongest case of mobility asymmetry, and it produces an enormous diffusion-potential field.
## The exclusion zone crystal
The field organizes the adjacent liquid into a honeycomb crystal, ~300 µm thick, with layers shifted by a full oxygen. The stacking must be ABC — in AB stacking, each oxygen would need five bonds (three in-plane, one up, one down), which oxygen cannot form. ABC avoids this by placing the nodes above and below at different lateral positions. The hexagonal openings are cross-linked by bridging waters.
In the honeycomb, the ring oxygens (δ⁻) sit on the vertices while the hydrogens (δ⁺) point partly inward along the edges. The interior of each hexagon is a positive electrostatic pocket.
The bridging water sits at the center of this pocket. It can only bond vertically — to the layers above and below. In the ground state, the bridge is OH⁻ — stabilized by the ring's positive pocket. The layer oxygen below is H₃O⁺, with its extra H pointing toward the adsorbate, along the field. The chain alternates: OH⁻, H₂O, H₃O⁺, OH⁻, H₂O, H₃O⁺. Every vertical hydrogen points the same direction.
This polarized configuration is the ground state — it is what makes the exclusion zone stable. The polarized chains, orientation-locked by the electric field, act as columns that hold the honeycomb layers together. The electrostatic field in the ring stabilizes the bridging OH⁻: a negative ion centered in a positive pocket. In ABC stacking, every oxygen sits in or adjacent to a hexagonal center — all are part of through-going chains, giving three oriented dipoles per unit cell.
Electron diffraction shows hexagonal symmetry with electron density in the hexagonal centers (McGeoch & McGeoch, 2008). In projection, this is what one expects from honeycomb layers shifted by a full oxygen — nodes from adjacent layers fall into the hexagonal openings of the layer in front. In ice-like stacking, the hexagonal centers form a vertical column. A chain of H₂O through this column is not possible — hydrogen would meet hydrogen between adjacent molecules. An OH⁻/H₃O⁺ alternation is also not possible — H₃O⁺ does not fit in the column. The full-oxygen-shift ABC structure resolves both problems: the honeycomb lattice accommodates H₃O⁺, OH⁻ sits in the hexagonal centers, and the diffusion-potential field stabilizes the alternation. Full-oxygen-shift stacking is required. AB full-shift would produce the same projection, but cannot exist (the five-bond problem). Only ABC can. The measured d-spacing of 3.73 Å is compressed relative to normal ice (3.9 Å), consistent with the ring being drawn inward by the negative charge at its center.
## An anisotropic proton conductor
A hydrogen bond is a shared proton. An ordered network of oriented hydrogen bonds is a proton conductor. These are the same statement in two languages.
The ABC stacking means that direct node-to-node connections between adjacent layers strictly alternate with passages through hexagonal openings — never two of the same in a row. With bridging waters in place, the proton chain runs: layer-O → bridge-O → layer-O → bridge-O, with all hops equivalent.
In bulk water, Grotthuss conduction is limited by two bottlenecks: rotation of the receiving molecule to orient the next bond, and reorganization of the solvation shell around the new and old proton positions. The crystal eliminates solvation/desolvation entirely — the lattice is the solvation shell, and it is fixed.
The conduction is anisotropic: along the chains perpendicular to the surface only. Within the honeycomb plane, the structure is an insulator.
## Conduction mechanism
Each OH⁻ in the chain is a hole — it can accept a proton. When H⁺ arrives at an OH⁻ bridge, the bridge becomes H₂O — and now has a hydrogen pointing directly at the H₃O⁺ below. H meets H. This repulsion cannot be sustained. The H₃O⁺ must release its H downward — but that hits the next OH⁻, which becomes H₂O with H pointing at the next H₃O⁺.
The entire chain must move as a single concerted motion — all bridges rotating and all protons hopping simultaneously. It is a collective mode, not a sequential cascade.
## Screening
The stable equilibrium of the deprotonated honeycomb adsorbate corresponds to approximately 50% ionization (Nygren, 2026). The proton-conducting crystal provides spatial separation between the retained OH⁻ in the adsorbate and the released H⁺ — which is transported through the exclusion zone and delivered to the bulk liquid. This accounts quantitatively for the H⁺ release measured from exclusion zones (Chai et al., 2009; Nygren, 2026).
The unscreened field from the adsorbate's charge separation is enormous (~100 MV across the exclusion zone). The measured field is on the order of millivolts (Zheng et al., 2006). Something cancels nearly all of it.
The polarized exclusion zone acts as a dielectric. Every oxygen in the crystal forms a polarized column — continuous chains of OH⁻, H₂O, H₃O⁺ repeating through the entire thickness — giving three oriented dipoles per unit cell. The resulting surface charge density is ~2.4 C/m². The adsorbate's surface charge density depends on its thickness. The polarization matches the adsorbate's field for an adsorbate thickness of ~1 nm at 50% ionization — consistent with a 3–4 layer adsorbate.
## References
Chai, B., Yoo, H., & Pollack, G. H. (2009). Effect of radiant energy on near-surface water. *The Journal of Physical Chemistry B,* 113(42), 13953–13958.
McGeoch, J. E., & McGeoch, M. W. (2008). Entrapment of water by subunit c of ATP synthase. *Journal of the Royal Society Interface,* 5(20), 311–318.
Nygren, J. (2026). Diffusion potential of autoionization at adsorbate-liquid interface in polar liquids. *Phanerography Certification.* BTC/BSV/ETH/ETC/LTC/DOGE/XTZ/EOS. hashkey:2f61914ae079f073dccabeed03bbfd558ecde0ec761f9a49645edb32b174b295 (sha256).
Pollack, G. H. (2013). *The Fourth Phase of Water: Beyond Solid, Liquid, and Vapor.* Ebner & Sons.
Zheng, J., Chin, W.-C., Khijniak, E., Khijniak, E., Jr., & Pollack, G. H. (2006). Surfaces and interfacial water: Evidence that hydrophilic surfaces have long-range impact. *Advances in Colloid and Interface Science,* 127(1), 19–27.