Choice of Electrolyte Impacts the Selectivity of Proton-Coupled Electrochemical Reactions on Hydrogen Titanate
Summary¶
Proton-coupled electrochemistry on layered oxides depends sensitively on electrolyte speciation because acids modulate both Faradaic selectivity and parasitic hydrogen evolution or dissolution. This Journal of Physical Chemistry C article examines hydrogen titanate H₂Ti₃O₇ electrodes in 1 M phosphoric acid versus 1 M sulfuric acid, combining cyclic voltammetry, galvanostatic cycling, and materials characterization with ReaxFF molecular dynamics of the electrode–electrolyte interface. Yun Kyung Shin and Adri C. T. van Duin contribute the reactive modeling leg alongside experimental collaborators led by Veronica Augustyn. A separate wiki slug may register an alternate proof PDF for the same DOI; this page tracks the issue-aligned PDF path in frontmatter for operators who attach the publisher file locally.
Methods¶
Electrode synthesis and electrochemical testing¶
H\(_2\)Ti\(_3\)O\(_7\) prepared from Na\(_2\)Ti\(_3\)O\(_7\) via solid-state + ion-exchange routes (Experimental section). Aqueous cells with Ag/AgCl reference; compare 1 M H\(_2\)SO\(_4\) vs buffered 1 M H\(_3\)PO\(_4\) at matched protocol choices.
Ex situ characterization¶
XRD, SEM, Raman, XPS, ICP-OES for phase, morphology, surface chemistry, and Ti dissolution.
ReaxFF interfacial MD (B)¶
Explicit electrolyte–surface models resolving water, acid anions, and protonation motifs; parameter extension and Ti(III) surrogate details in [[2023fortunato-venue-paper]] (SI PDF).
1 — MD application (atomistic dynamics) — interfacial leg¶
Engine / code: LAMMPS with ReaxFF (extended parameterization for H–Ti–O/acid chemistry as in the SI / companion slug). System & composition: H\(_2\)Ti\(_3\)O\(_7\)-water–electrolyte (H\(_2\)SO\(_4\) or H\(_3\)PO\(_4\)) interfacial cells. Boundaries / periodicity: in-plane PBC for slab/surface supercells. Ensemble, timestep, thermostat, duration: N/A on this page—SI simulation cells in [[2023fortunato-venue-paper]] document NVT-class sampling and numerical controls; the main text figures give qualitative structure. Barostat, pressure, shear, shock: N/A in this interfacial NVT-like summary. Temperature: near ambient aqueous interface (as in SI) unless otherwise stated. External electric field in MD: N/A — the experiment applies galvanostatic/CV bias; the ReaxFF work supports speciation/association at the unbiased-slab or mild-driving level described in the article/SI, not a full device field map. Coulomb / ReaxFF QEq: as implemented for the FF in use. Enhanced sampling: N/A here.
2 — Force-field training¶
N/A on this issue-PDF page; new or reweighted terms and DFT training data are in [[2023fortunato-venue-paper]] and related SI.
3 — Static QM¶
N/A in this work’s modeling core; DFT may appear in prior HTO literature elsewhere as cited, but the paper’s new atomistic leg is ReaxFF MD.
Findings¶
Electrochemical metrics (abstract)¶
Average Coulombic efficiency improves ~48% → 71% and capacity ~83 → 90 mAh g\(^{-1}\) when switching H\(_2\)SO\(_4\) → H\(_3\)PO\(_4\) at the stated concentrations.
Experimental interpretation¶
Phosphoric media are argued to buffer interfacial acidity and reduce HER/HTO dissolution vs strongly acidic sulfate.
Atomistic support (qualitative)¶
ReaxFF trajectories favor stronger phosphate interfacial association vs sulfate, altering proton availability and surface passivation—see main-text figures for structural detail.
Limitations¶
Atomistic trajectories cannot span hour-scale dissolution or reprecipitation kinetics observed in cells, nor do they fully resolve porous-electrode transport and local pH gradients; conclusions are therefore mechanistic complements to experiment rather than digital twins of full devices.
Relevance to group¶
The study is a primary archival reference for Shin and van Duin ReaxFF modeling of aqueous acid interfaces on titanate proton-storage hosts, linking electrochemistry tags to reactive MD in the corpus.
MAS / retrieval notes¶
When this page appears alongside duplicate slugs for the same DOI, prefer the issue PDF path recorded in normalized/papers after sync; quote electrochemical metrics with units exactly as printed in the abstract (mAh g⁻¹, Coulombic efficiency) and point users to SI simulation cells for ReaxFF boundary conditions.