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.

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.

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.

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.

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.

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... 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.

Saponins are natural products that consist of triterpene or sterol cores decorated with oxidations, glycosylations, and sometimes other modifications. Many saponins are utilized as nutraceutics (e.g., glycyrrhizin) or therapeutics (e.g., QS-21 and digitoxin/digoxin). The structure-activity relationships that govern saponin bioactivity can be identified by studying structurally related saponins; however, the production of varied sets of saponins remains challenging via either chemical (semi)synthesis or native/heterologous biosynthesis. This report describes the discovery that the GT1 family enzyme GuUGT73F15 (Glycyrrhiza uralensis) can be used to biosynthesize many different saponins via triterpene/sterol C3 β-O-glycosylation. GuUGT73F15 utilized 22 sugar acceptors (C3 hydroxyl-containing triterpenes/sterols) and 12 sugar donors (uridine diphosphate [UDP]-sugars) as substrates to produce 130 unique monoglycosylated saponins, of which more than 100 have not been reported as natural products to the best of our knowledge. GuUGT73F15 also accepted 13 cyclohexanol- and phenol-type molecules as minimized sugar acceptors. Based on Boltz-2x predictions, the broad substrate scope of GuUGT73F15 is hypothesized to arise from its varied sugar acceptor binding poses and consistent sugar donor binding poses. Applications of broad C3 β-O-glycosylation activity were exemplified via the production of antibody-saponin conjugates as well as the in vivo microbial biosynthesis and the in vitro biosynthesis of advanced QS-21 intermediates. Together, GuUGT73F15 is a versatile biocatalytic tool that can be utilized to produce libraries of high-value saponin natural products and new-to-nature saponins.

Herein, we report two heterometallic ultramicroporous metal-organic frameworks, MIP-212(Al/Cu) and MIP-212(Al/Zn) (MIP stands for Materials from Institute of Porous Materials of Paris), synthesized via a hard-soft acid-base design strategy. In these robust pyrazolate-carboxylate architectures, pyrazolates selectively coordinate Cu²⁺ or Zn²⁺, while carboxylates bind Al³⁺, generating chain-based inorganic building units built up from connected M²⁺-pyrazolate polyhedra and μ₂-OH-corner-shared AlO₆ octahedra, respectively. The resulting structures feature dual ultranarrow tunnel-like pores, one decorated with μ₂-OH groups. MIP-212(Al/Cu) combines pore confinement with Cu²⁺ open metal sites (OMS) to deliver benchmark-level CO₂ uptake at low pressure (2.30 mmol g^-1 at 0.15 bar, 298 K) and a CO₂/N₂ Ideal Adsorbed Solution Theory (IAST) selectivity of ∼30. However, the OMS also imparts marked hydrophilicity, diminishing CO₂ uptake under humid conditions. Markedly, replacing octahedral Cu²⁺ with tetrahedral Zn²⁺ centers in MIP-212(Al/Zn) suppresses OMS while preserving framework topology, resulting in significantly lower water affinity (up to ca. 4-fold reduction at 0.2 bar of H₂O) and superior CO₂ breakthrough performance at 50% RH. These findings demonstrate that metal coordination geometry is a powerful lever to modulate hydrophilicity and sorption behavior in MOFs, enabling the rational design of sorbents for efficient CO₂ capture under realistic, moisture-rich environments.

Bipolar membranes (BPMs) create counteracting spatial gradients of pH and electrostatic potential in electrochemical systems, enabling applications in pH regulation, electrocatalysis, and separations. At the polarized junction of a BPM the water dissociation (WD, 2H₂O ⇌ H₃O⁺ + OH^-) reaction can be driven, but it remains poorly understood. In this Perspective, we integrate molecular insights from bulk-water autoionization and the associated field effects with continuum descriptions of BPM electrostatics and experimental WD kinetic analyses to describe possible mechanisms of voltage-driven WD. Pristine BPM junctions highlight both the limits of primarily electric-field-driven WD and the practical challenges of junction stability at extreme reverse bias. Introducing heterogeneous catalyst layers, commonly metal oxides and graphene oxides, accelerates WD by orders of magnitude through hypothesized coupled effects in which surface acid-base functionality and high-density hydroxyl sites mediate proton-transfer steps, and catalyst mobile electronic/ionic charges redistribute the junction electric potential drop to shape the local electric fields and reactive microenvironments. Kinetic analyses suggest two regimes of heterogeneous WD mechanism, including field-driven ordering of interfacial water and a Second-Wien-Effect dissociation-barrier lowering. We conclude by defining the key unknown variables (local pH, electrostatic potential, catalyst charge state and relationships among mechanisms) and outlining experimental and multiscale modeling strategies needed for predictive WD catalysis and for controlling related ion-transfer reactions.