College of Chemistry

We introduce a benchtop NMR method for interferometric detection of geometric phase (also known as Berry/Aharonov-Anandan phase) via spin coherence holonomy in bulk ensembles using phase-wound echo trains. Consecutive π pulses with cyclic phase incrementation drive closed spinor trajectories on the Bloch sphere, while a parity-based analysis isolates the geometric contribution and cancels dynamical offsets by comparing positive and negative winding experiments with a zero-winding reference. The extracted phase increases linearly with echo number, reverses sign under winding reversal, and is independent of echo time in the adiabatic regime, consistent with spinor holonomy arising from parallel transport. Experiments performed in strongly inhomogeneous, low-field conditions demonstrate robustness to B₀ gradients and diffusion. This approach establishes a practical foundation for probing geometric phase effects in NMR, with extensions to non-adiabatic transport, heterogeneous systems, and quantum sensing applications.

We show that the pH gradient at the catalyst–ion exchange membrane interface in a seawater bipolar-membrane electrolyzer can be mitigated by reducing the catalyst–membrane distance. We further show how water transport can be balanced at steady state. Bipolar membrane (BPM) electrolyzers offer advantages in the electrolysis of impure-waters by controlling ion flux, yet still suffer from performance and durabilty limitations. Here, we investigate the impact of NaCl electrolyte (nominally simulated seawater) on BPM electrolyzer operation and identify local pH gradients at electrode–membrane interfaces, arising from coupled ion transport and electrode reactions, as one origin of performance loss and degradation. NaCl in the catholyte induces pronounced pH gradients at the cathode|cation-exchange-layer interface, leading to increased voltage, while partial Cl − crossover to the anode becomes detrimental under locally OH − -deficient conditions, promoting the chlorine evolution reaction and accelerating degradation. Direct physical integration of the cathode and anode catalysts onto the cation and anion exchange layers through spray coating and electrodeposition, respectively, mitigates these effects by minimizing the membrane–catalyst distance. The BPM electrolyzer built in this way achieves 0.50 A cm −2 at 2.8 V and shows a degradation rate of 5.5 mV h −1 over 120 h in 0.50 M NaCl electrolyte, compared to degradation of 71 mV h −1 with a typical porous-transport-layer device structure. This work thus establishes control of local pH gradients as a design principle for BPM electrolysis with impure-water feeds.

Cu/ZnO/Al 2 O 3 catalysts are commonly used for methanol synthesis, yet the chemical state of the Cu|ZnO interface remains debated. We probe Cu|ZnO interfacial chemistry by measuring junction electrical characteristics under N 2 , CO 2 and gas mixtures from 50 to 250 °C and up to 10 bar(a). The pristine interface behaves as a nonideal rectifying Schottky diode, and H 2 exposure drives a reversible transition toward ohmic behavior, with increased apparent n-type donor density in the ZnO and lower Schottky-barrier height. This result implies the electric potential at the putative active-catalyst interface decreases under reactive conditions. Recovery of rectifying behavior under O 2 and H 2 -free N 2 or CO 2 argues against persistent Cu–Zn alloying or oxygen-vacancy formation and supports reversible hydrogen doping of ZnO. CO 2 slows H insertion into ZnO relative to N 2 , while water strongly suppresses it. Junction electrical measurements thus inform how such catalytic interfaces evolve under reactive conditions.

Abstract Operation-induced surface reconstruction of photoelectrodes is underexplored as a path to control stability and performance. We show how adaptive junctions form via surface reconstruction of BiVO4 during glycerol photooxidation and how these surfaces affect electrolyte-dependent kinetics and durability. Preferential V dissolution in both acidic and alkaline media forms a Bi-rich layer. In situ measurements through a dual-working-electrode platform quantify the changes in photovoltage and charge-transfer resistance derived from adaptive junction formation, while enabling quantitative separation of the driving forces for charge separation and interfacial catalysis. The reconstructed surface in acidic media improves hole-transfer kinetics, functions as a glycerol-oxidation catalyst, and imparts photostability. Surface reconstruction in alkaline media exhibits the opposite behavior, impeding hole injection. This instability is mitigated by trace Ni2+ ions, which drive in situ surface activation without cocatalyst pre-deposition. This study shows the significance of surface reconstruction in the design of durable photoelectrodes for applications targeting organic electro-oxidation.

Abstract Nanoconfined fluids, particularly water, govern subsurface geochemistry, yet the molecular-level mechanisms by which mineral surfaces dictate confined water structure and mobility remain poorly resolved. Here, we combine solution- and solid-state proton (1H) NMR spectroscopy, NMR relaxometry, modulated-gradient spin–echo (MGSE) NMR diffusometry, infrared spectroscopy, and molecular dynamics simulations to demonstrate that surface hydroxyls drive the structural and dynamic differentiation of water in imogolite nanotubes. In saturated suspensions, we observe the coexistence of distinct water 1H environments, each exhibiting significantly reduced mobility, which we attribute to strong interactions with the imogolite surfaces. As more mobile water is removed, long-range water diffusivity in the fibrous solid samples slows to 1.6 × 10–10 m2·s–1 while local fluctuations increase to 3.4 × 10–8 m2·s–1, indicating a significant increase in molecular restriction through surface interactions. Together, our experiments reveal three coexisting populations with varied structures and mobilities, all distinct from liquid bulk water. We resolve a persistent solid-like interfacial layer strongly bound to surface hydroxyls, characterized by an unusually short T2 (<1 ms), and a very close effective 1H–1H distance of ∼1.55 Å between water and the inner-surface silanol group. An inner-core population occupying the inner cavity exhibits an intermediate dynamic regime with restricted axial diffusion, while outer-surface water associated with aluminum hydroxyls retains relatively higher mobility. These results experimentally substantiate a hierarchy of water populations in imogolite and show how surface chemistry dictates the structures and dynamics of confined water.

Ring-disk electrode experiments and Raman spectroscopy suggest a potential passivation process that limits soluble Fe 2+ formed from magnetite. Reprecipitation of inactive ores enables ironmaking at rates >100 mA cm −2 in stagnant electrolytes. Low-temperature electrochemical cells reducing iron oxides to metal in alkaline electrolytes can support fully electrified steelmaking processes. Previous studies on these cells have primarily focused on high-surface-area hematite, Fe 2 O 3 , reactants whereas attempts to reduce suspensions of magnetite, Fe 3 O 4 —one of the two feedstocks for existing ironmaking reactors—have generally been limited to low rates of reaction (<30 mA cm −2 ). Here, we control the crystalline domain size of Fe 2 O 3 and Fe 3 O 4 particles in 10 M NaOH electrolytes to study how the nanoscale morphology of oxides controls the rate of electrochemical ironmaking. Rotating-ring disk electrode measurements of Fe 2+ , in situ Raman spectroscopy of the electrode surface, and ex situ electron microscopy were consistent with a hypothesized passivation process at Fe 3 O 4 surfaces that may prevent the continuous formation of soluble intermediates. Sufficiently small (<100 nm diameter) oxide particles yielded Fe partial current densities >160 mA cm −2 , a fivefold increase relative to previously reported rates for Fe 3 O 4 suspensions and comparable to active Fe 2 O 3 . Electron microscopy revealed that electrodeposited films were composed of micron-scale crystalline Fe domains with a porous film of Fe 3 O 4 nanoparticles and supports a model where Fe is grown primarily from soluble Fe 2+ intermediates. Based on these insights, inactive blast-furnace-grade iron-oxides were transformed into high surface area nanoparticles (1.6 to 229.2 m 2 g −1 ) via reprecipitation, leading to a ninefold enhancement in faradaic efficiency and an Fe partial current density of 120 mA cm −2 . When integrated with chlor-iron cells producing reagents for reprecipitation, this approach could lead to a cost-competitive process for electrochemical ironmaking from industrially relevant feedstocks.

ABSTRACT Disordered rocksalt cathodes hold promise for achieving high‐capacity lithium‐ion batteries while using low‐cost, earth‐abundant elements. However, their electrochemical performance remains critically limited by their poor electronic conductivity. Conventional strategies such as high‐energy ball milling with excess carbon additives can improve conductivity but remain challenging to scale and often produce defects and increase surface area, thereby accelerating capacity degradation. Herein, we report an alternative approach of electrostatic‐attraction‐driven self‐assembly to fabricate Li 1.2 Mn 0.6 Ti 0.2 O 1.8 F 0.2 (LMTOF) particles uniformly wrapped with electronically conductive graphene sheets without associated materials degradation. The graphene‐wrapped LMTOF demonstrates significantly improved cycling stability (89% capacity retention after 100 cycles) and superior rate capability compared with an LMTOF‐carbon composite electrode fabricated using the conventional high‐energy ball‐milling process. Post‐cycling analysis reveals reduced oxygen evolution, suppressed unwanted side reactions, and improved structural integrity for the graphene‐LMTOF composite. This work highlights the advantages of solution‐based carbon wrapping and offers a scalable strategy to prepare high‐performance DRX cathodes for lithium‐ion batteries.

There is considerable interest in developing high-performance electrolytes for rechargeable lithium batteries. For practical applications, the electrolyte must support large dc currents. However, the parameters most often reported in the literature, conductivity, κ, and current fraction, ρ+, reflect ion transport in the limit of infinitesimal currents. In this limit, the efficacy of an electrolyte is given by the product κρ+. The limiting current density, i lim, is the maximum current density that can be applied across an electrolyte; the cell voltage diverges if the applied current density exceeds i lim. This parameter reflects ion transport in the limit of large dc currents and is therefore of practical interest. It would therefore be convenient if i lim could be predicted from measurements of κρ+. In order to explore this possibility, we studied six malonate-based polymers and PEO at a fixed salt concentration (r = 0.08) and temperature (90°C) using symmetric cells with planar electrodes. Unfortunately, there is no correlation between i lim and κρ+. When the applied current density, i, is less than i lim, the cell voltage approaches a stable plateau, ϕplateau. We found a linear dependence between i and thickness-normalized plateau potential, ϕplateau L –1, irrespective of the magnitude of the applied current. In all seven polymer electrolytes, we found a linear correlation between i lim and the slopes of these lines, σ. In other words, measurements of σ can be used to predict the limiting current.

Organic ionic plastic crystal electrolytes, containing a plastic crystal and lithium salt, offer a potential balance between mechanical and electrochemical properties for solid state lithium-ion battery electrolytes. These electrolytes contain multiple mobile ionic species (three or four), resulting in complex transport mechanisms which have not yet been established. Plastic crystals are defined by long-range positional order and short-range rotational disorder. It is therefore necessary to quantify changes in the local crystal structure of the electrolyte as current flows through it. Herein, we examine the electrochemical properties of pyrrolidinium-based plastic crystal electrolytes containing lithium salt and zwitterion additives, including measurements of current fraction and limiting current. We obtain species-specific insight into electrolyte transport using pulsed-field gradient nuclear magnetic resonance spectroscopy and find that, while the zwitterion additive increases ionic conductivity, it decreases lithium diffusivity with respect to other ionic components. With operando spatiotemporally resolved wide-angle X-ray scattering we observe location-specific crystal rotations due to the passage of ionic current. We posit that reducing energy dissipation due to rotation is essential for using plastic crystal electrolytes in practical applications.

Abstract Bipolar membranes (BPMs) enable electrochemical systems that operate across large pH gradients; however, high-current operation is often limited by voltage losses whose origins remain difficult to resolve in membrane−electrode assemblies. Here, we combine electrochemical impedance spectroscopy with distribution of relaxation times (EIS–DRT) analysis and operando synchrotron X-ray diffraction to examine interfacial polarization, membrane hydration, and transport in commercial and synthesized BPMs. EIS–DRT isolates the BPM-associated interfacial contribution and shows that the commercial BPM exhibits larger water-dissociation-associated overpotentials than the synthesized BPM. Operando hydration mapping shows that both membranes retain water at the bipolar junction during high-current operation, while anode-adjacent hydration gradients are more pronounced in the commercial membrane. These results indicate that high-current voltage losses are not governed by junction water starvation alone but by coupled interfacial polarization and transport resistances.