Wei Wang

Organic electrode materials (OEMs) offer a sustainable alternative to inorganic cathodes but typically suffer from low intrinsic electronic conductivity. The material historically reported as bis‐tetraaminobenzoquinone (TAQ) exhibits bulk conductivity two orders of magnitude higher than its close analogue tetraaminophenazine‐tetraone (TAPT), despite their common precursor and nearly identical short‐range structure. This disparity has previously been attributed to distinct molecular skeletons, with TAQ proposed to adopt a piperazine‐type linkage and TAPT a pyrazine ring. Here, combining synchrotron x‐ray scattering, solid‐state ¹⁵ N and ¹³ C nuclear magnetic resonance (NMR), microcrystal electron diffraction (MicroED), continuous‐wave and pulsed electron paramagnetic resonance (EPR) spectroscopy, we show that “TAQ” has the same pyrazine‐based molecular structure as TAPT, with no evidence for piperazine core or keto–enol tautomerization. Their key difference lies in synthesis‐dependent degree of crystallinity: “TAQ” exhibits greater long‐range structural coherence and a crystallographically resolved intermolecular hydrogen‐bonding network, whereas TAPT is more disordered. EPR further shows that the higher structural order in “TAQ” is associated with a strongly delocalized π‐spin manifold, while TAPT favors localized or weakly delocalized radicals and stronger local spin coupling. These findings identify degree of crystallinity and hydrogen‐bonding order as key structural features associated with radical delocalization and enhanced conductivity in organic electrodes.

Organic electrode materials (OEMs) offer a sustainable alternative to inorganic cathodes but typically suffer from low intrinsic electronic conductivity. The material historically reported as bis‐tetraaminobenzoquinone (TAQ) exhibits bulk conductivity two orders of magnitude higher than its close analogue tetraaminophenazine‐tetraone (TAPT), despite their common precursor and nearly identical short‐range structure. This disparity has previously been attributed to distinct molecular skeletons, with TAQ proposed to adopt a piperazine‐type linkage and TAPT a pyrazine ring. Here, combining synchrotron x‐ray scattering, solid‐state ¹⁵ N and ¹³ C nuclear magnetic resonance (NMR), microcrystal electron diffraction (MicroED), continuous‐wave and pulsed electron paramagnetic resonance (EPR) spectroscopy, we show that “TAQ” has the same pyrazine‐based molecular structure as TAPT, with no evidence for piperazine core or keto–enol tautomerization. Their key difference lies in synthesis‐dependent degree of crystallinity: “TAQ” exhibits greater long‐range structural coherence and a crystallographically resolved intermolecular hydrogen‐bonding network, whereas TAPT is more disordered. EPR further shows that the higher structural order in “TAQ” is associated with a strongly delocalized π‐spin manifold, while TAPT favors localized or weakly delocalized radicals and stronger local spin coupling. These findings identify degree of crystallinity and hydrogen‐bonding order as key structural features associated with radical delocalization and enhanced conductivity in organic electrodes.

Redox-active organic molecules provide a versatile platform for applications such as organocatalysis, electrocatalysis, and energy storage; however, parasitic reactions can yield competing bond-forming pathways that trap the molecule in electrochemically inaccessible states, passivating the redox electrochemical reversibility. Reductive radical coupling exemplifies this challenge. Although carbonyl reduction to an alcohol is a standard chemically reversible process, electrochemical reduction can induce radical coupling that leads to C–C bond formation, effectively diverting the reaction from the canonical two-electron, two-proton pathway and from electrochemical reversibility. Here, we demonstrate an electron-abstraction mechanism in which the mediator activates chemically reversible, yet electrochemically irreversible C–C bond scission with an estimated apparent rate constant of 3.54 × 10–6 M–1 s–1 under the tested conditions, which supports the restoration of “net” electrochemical reversibility and bypasses the large kinetic activation barrier in electrochemical systems. A flow battery configuration is used to illustrate how this mediating strategy enhances energy efficiency in electrochemical systems by bypassing high-kinetic barrier reaction pathways. Spectroscopic analyses directly capture both C–C bond formation and dissociation, while density functional theory calculations suggest an electron-abstraction mechanism for C–C bond cleavage. The demonstrated mediated, reversible C–C bond cleavage highlights a mechanistic proof-of-concept for overcoming high kinetic activation barriers in otherwise sluggish chemical transformations under electrochemical conditions.

The feasibility of using TEMPO catholyte in long-cycling aqueous redox flow batteries depends on the effective mitigation of the ring-opening side reactions.

Mediated electron transfer (MET) plays a crucial role in energy storage and conversion technologies such as redox targeting flow batteries (RTFBs), yet its experimental investigation often requires labor-intensive and low-throughput setups. To address this, we developed a microfabricated interdigitated electrode array (IDA) platform that enables automated, high-throughput electrochemical redox titration measurement to be performed to study the MET process. Our redox titration method enables simultaneous measurement of the charge capacity and rate of MET processes on a material or surface. Automated redox titration (ART) facilitates systematic investigation of the MET process across a broad parameter space, exemplified through the study of polypyrrole (PPy) and a pyrene-4,5,9,10-tetrone azo group-based polymer (PTAP), both redox-active polymers relevant to various energy storage applications. Using PPy as a model material, 500 redox titration measurements were conducted within 50 h, varying the electrode gap widths, polymer charging potentials, voltammetric scan rates, and electrolyte concentrations. Finite-element simulations confirmed the electrochemical responses and elucidated the kinetics of the MET reactions. Our automated methodology was further tested with PTAP, revealing a surprising charging potential dependence on the rate of MET. The automation, flexibility, and scalability of our redox titration platform pave the way not only for advanced studies of MET processes relevant to RTFBs, but also with implications in the understanding of next-generation energy storage materials, molecular electrocatalysis, and biosensing.

Glucose as a biofuel offers unique advantages, including low-temperature electricity generation, easy accessibility, low storage cost, and adaptability for on-demand power generation. Riboflavin, commonly known as Vitamin B₂, is a critical component in biological systems, participating in many metabolic reactions as an enzyme cofactor. Drawing inspiration from these metabolic processes, we demonstrate a flow cell for the electrochemical glucose oxidation reaction (GOR), using riboflavin as an environmentally friendly mediator to replace traditional noble metal catalysts. When pairing with an O₂ electrode under alkaline conditions, the glucose flow cell achieves a peak power density of 13 mW/cm², 20 times greater than the previously reported value under similar conditions. The demonstrated vitamin-mediated biofuel flow cell introduces a new catalytic design approach for a glucose-based biofuel cell, delivering high peak power density at room temperature and ambient pressure. This approach ensures low cost and environmental sustainability, eliminating the need for noble metal catalysts.

An autonomous synthesis of organic flow battery molecules using flexible batch Bayesian optimization to handle varying variables sizes in a single batch.

Thick electrodes are critical for long-duration energy storage, but their practical development is hindered by sluggish ion transport and elevated viscosity. Here, we present a solvation-based design strategy—Localized Diluted Electrolytes (LDEs)—that decouples ionic mobility from bulk viscosity through spatially engineered solvation heterogeneity. By promoting the nanoscale preferential distribution of salt-rich and water-rich domains, the LDE approach forms interconnected water-rich regions that sustain fluid-like ionic transport within a mechanically constrained gel matrix. Implemented in a zinc-iodine (Zn-I2) polymeric framework gel battery, this design enables a 2-mm-thick monolithic gel electrode with an areal capacity of ~ 28 mAh/cm² and an energy density of ~ 240 Wh/L based on cathode materials (~ 153 Wh/L for a full cell), achieving stable long-duration cycling. Nuclear magnetic resonance (NMR) spectroscopy, molecular dynamics simulations, and electrochemical analyses confirm rapid, sustained water and ion mobility throughout the polymer network, despite ~ 1200-fold increase in viscosity compared to the liquid-phase electrolyte. This work redefines how solvation environments can be spatially structured to decouple ionic transport from viscosity-driven limitations, establishing a new framework for electrolyte design.