{
  "annotation_id": "d422d57d-f5d3-4a0e-aad8-3b7e9ecbfffc",
  "date_created": "2026-02-17T05:53:08.863000Z",
  "date_modified": "2026-02-17T05:53:08.863000Z",
  "file_hash": "5a2c44b9a92fb57a472af3a6b2011e1ab472a14d1c3d3b841f9b2a9f1ae41765",
  "private": false,
  "record": {
    "abstract": "The distribution of ions and their impact on the structure of electrolyte interfaces plays an important role in many applications. Interestingly, recent experimental studies have suggested the preferential accumulation of $SO_4^{2-}$ ions at the $Na_2SO_{4,aq}$-graphene interface in disagreement with the generally known tendency of cations to accumulate at graphene-electrolyte interfaces. Herein, we resolve the atomistic structure of the $Na_2SO_{4,aq}$-graphene interfaces in the 0.1-2.0 M concentration range using machine learning interatomic potential-based simulations and simulated sum frequency generation (SFG) spectra to reveal the molecular origins of the conundrum. Our results show that Na+ ions accumulate between the outermost and second water layers whereas $SO_4^{2-}$ ions accumulate within the second interfacial water layer indicating cation dominated interfaces. We find that the interfacial region (within ~10 ${\\AA}$ of the graphene sheet) is negatively charged due to sub-stoichiometric $Na^+$/$SO_4^{2-}$ ratio at the interface. Our simulated SFG spectra show enhancement and a red-shift of the spectra in the hydrogen bonded region as a function of $Na_2SO_4$ concentration similar to measurements due to $SO_4^{2-}$-induced changes in the orientational order of water molecules in the second interfacial layer. Our study demonstrates that ion stratification and ion-induced water reorganization are key elements of understanding the electrolyte-graphene interface.",
    "arxiv_id": "2601.06995",
    "authors": [
      "Ademola Soyemi",
      "Tibor Szilvasi"
    ],
    "categories": [
      "physics.chem-ph",
      "cond-mat.mtrl-sci"
    ],
    "license": "http://creativecommons.org/licenses/by-nc-nd/4.0/",
    "title": "Cation Dominated but Negatively Charged Na2SO4,aq-Graphene Interfaces",
    "url": "https://arxiv.org/abs/2601.06995",
    "version": "v1"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "e6c2cd79-e9f4-4d3e-8225-0cf2bdd0eb9c",
    "id": "arXiv Dataset",
    "type": "Model",
    "variant": "snapshot-2026-01-17",
    "version": "0.1.0"
  },
  "user_id": 1000002
}