Yuyan Shao

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.

Bipolar plates (BPs) are among the most expensive components in redox flow battery (RFB) stacks, alongside membranes. In vanadium flow batteries (VFBs), graphite and carbon composite materials have been widely used for BPs due to their excellent corrosion resistance. However, these materials are costly, difficult to machine, and relatively thick. While VFBs have reached commercialization, their broader deployment is hindered by the high cost of vanadium.

Enhancing the catalytic stability of Fe-N-C catalysts for cathodic oxygen reduction in proton-exchange membrane fuel cells (PEMFCs) necessitates an in-depth understanding of their degradation mechanisms. This study identifies key stressors affecting the stability of Fe-N-C catalysts, specifically acidic environment, oxygen (O₂), and reactive oxygen species (ROS). Through ex situ/operando experiments, we show that the oxidation of local carbon by acidic environment + O₂ + ROS, along with the demetalation of catalytic FeN_xC_y sites by O₂ or O₂ + ROS, is the primary factor responsible for the initial fast degradation of Fe-N-C catalysts. The demetalation of FeN_xC_y sites, influenced by O₂, in particular by O₂ + ROS, leads to the subsequent gradual degradation of Fe-N-C. Notably, FeN₄C₁₂-type active sites are more susceptible to demetalation than FeN₄C₁₀-type sites in O₂ or O₂ + ROS. Our findings indicate that, besides constructing more stable FeN_xC_y sites, preventing local carbon oxidation and scavenging of ROS are all critical for maintaining the stability of Fe-N-C catalysts.

Atomic metal sites, such as Fe, Co, and Mn, coordinated with N and embedded in carbon, are the most promising platinum-group-metal (PGM)-free catalysts for acidic oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells. Among others, Mn sites are preferable to minimize potential Fenton reactions within the electrode. Herein, we demonstrate a facile and scalable synthetic method to prepare atomic Mn-N-C catalysts by directly converting manganese oxides into active, stable MnN ₄ sites via solid-state reactions. Post-treatment with ammonium chloride can enhance the intrinsic ORR activity of MnN _x moieties by introducing additional nitrogen groups and defects. Subsequent post-treatment with organic molecules, such as benzimidazole, promotes the formation of a robust carbon structure and significantly improves catalyst stability. The resulting Mn-N-C catalyst exhibits promising ORR activity, achieving a half-wave potential of 0.83 V vs RHE in aqueous 0.5 M H ₂ SO ₄ electrolyte, outperforming most PGM-free ORR catalysts. A corresponding membrane electrode assembly (MEA) generated a current density of ∼400 mA cm ⁻² at 0.67 V and a peak power density of 0.46 W cm ⁻² . Significantly, post-treatment with benzimidazole improved catalyst stability, retaining 85% of the MEA performance, although the initial performance was compromised.

Redox flow battery shows promise for grid-scale energy storage. Aqueous organic redox flow battery is particularly popular due to its potentially low material cost and safe water-based electrolyte. Commonly, redox-active molecules used in this field feature a simple redox mechanism. Our studies reveal an atypical redox mechanism: a coupled chemical electrochemical process, which activates traditionally considered redox-inert material to be an excellent battery material. We demonstrate the first homogeneous catalysis approach in a proton-coupled electron transfer process in the battery discharge process, with the development of novel in-operando characterization techniques. Our study also reveals the underlying π-π stacking effect in extended aromatic redox active compounds, where aromatic radical intermediates are involved in the redox process. The in-depth studies on fluorenone-based electrolytes open a new avenue for complexing redox mechanisms and extend the possibility to unconventional energy storage media.

High energy density aqueous batteries are promising candidates for grid energy storage, thanks to their potential low cost and ability to enhance grid resilience by providing extended power supply during natural disasters or other disruptions. However, the currently available aqueous electrochemical energy storage systems cannot meet the requirement of safety, cost, footprint, and capacity simultaneously. Here, we report a low-cost zinc-based aqueous battery featuring a polymer network that facilitates high ionic conductivity and supports the use of thick electrodes. The new zinc-based aqueous battery delivers a high energy density of >150 Wh/L. Simulations, characterization, and electrochemical performance data will be presented.

This review establishes weakly solvating electrolytes as a solvation-centric design paradigm, integrating DN/ ε /ESP descriptors to explain mechanisms, guide solvent selection, and unify strategies across Li, Na, K, Zn, and Mg batteries.

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.

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.