A Hybrid Redox-Mediated Zinc-Air Fuel Cell for Scalable and Sustained Power Generation.

Zinc-air batteries (ZABs) have attracted considerable attention for their high energy density, safety, low noise, and eco-friendliness. However, the capacity of mechanically rechargeable ZABs was limited by the cumbersome procedure for replacing the zinc anode, while electrically rechargeable ZABs suffer from issues including low depth of discharge, zinc dendrite and dead zinc formation, and sluggish oxygen evolution reaction, etc. To address these issues, we report a hybrid redox-mediated zinc-air fuel cell (HRM-ZAFC) utilizing 7,8-dihydroxyphenazine-2-sulfonic acid (DHPS) as the anolyte redox mediator, which shifts the zinc oxidation reaction from the electrode surface to a separate fuel tank. This approach decouples fuel feeding and electricity generation, providing greater operation flexibility and scalability for large-scale power generation applications. The DHPS-mediated ZAFC exhibited a superior peak power density of 0.51 W/cm2 and a continuous discharge capacity of 48.82 Ah with ZnO as the discharge product in the tank, highlighting its potential for power generation.

Ammonia Electrosynthesis from Nitrate Using a Ruthenium-Copper Cocatalyst System: A Full Concentration Range Study.

Electrochemical synthesis of ammonia via the nitrate reduction reaction (NO3RR) has been intensively researched as an alternative to the traditional Haber-Bosch process. Most research focuses on the low concentration range representative of the nitrate level in wastewater, leaving the high concentration range, which exists in nuclear and fertilizer wastes, unexplored. The use of a concentrated electrolyte (≥1 M) for higher rate production is hampered by poor hydrogen transfer kinetics. Herein, we demonstrate that a cocatalytic system of Ru/Cu2O catalyst enables NO3RR at 10.0 A in 1 M nitrate electrolyte in a 16 cm2 flow electrolyzer, with 100% faradaic efficiency toward ammonia. Detailed mechanistic studies by deuterium labeling and operando Fourier transform infrared (FTIR) spectroscopy allow us to probe the hydrogen transfer rate and intermediate species on Ru/Cu2O. Ab initio molecular dynamics (AIMD) simulations reveal that adsorbed hydroxide on Ru nanoparticles increases the density of the hydrogen-bonded water network near the Cu2O surface, which promotes the hydrogen transfer rate. Our work highlights the importance of engineering synergistic interactions in cocatalysts for addressing the kinetic bottleneck in electrosynthesis.

Redox Targeting-based Neutral Aqueous Flow Battery with High Energy Density and Low Cost.

Neutral aqueous flow batteries with common traits of the redox flow batteries, such as the independence of energy and power, scalability and operational flexibility, and additional merits of outstanding safety and low corrosivity show great promise for storing massive electrical energy from solar and wind energy. Particularly, the ferricyanide/ferrocyanide ([Fe(CN)6 ]3-/4- ) couple has been intensively employed as redox mediator to store energy in the catholyte ascribed to its abundance, low corrosivity, remarkable redox reversibility and stability. However, the low energy density arising from poor solubility of [Fe(CN)6 ]3-/4- restricts their commercial applications for energy storage systems. In this study, the practical energy density of a [Fe(CN)6 ]3-/4- -based catholyte is significantly boosted from 10.5 to 92.8 Wh L-1 by combining the counter-ion effect and the single-molecule redox-targeting (SMRT) reactions between [Fe(CN)6 ]3-/4- and Prussian blue (Fe4 [Fe(CN)6 ]3 , PB)/Prussian white (PW). Paired with concentrated K2 S anolyte, we demonstrate a neutral aqueous SMRT-based PB-Fe/S flow battery with ultra-long lifespan over 7000 cycles (4500 h) and ultra-low chemical cost of electrolytes in the cell as 19.26 $ kWh-1 . Remarkably, under the influences of SMRT reactions in the presence of PB granules in the catholyte, the capacity after 7000 cycles of the PB-Fe/S flow battery is 181.8 % of the initial capacity without PB.

Flow battery electrolyte from carbon black incineration fly ash: A feasibility study of an environment friendly disposal process.

Fly ash represents a kind of finely divided solid waste which is derived from industrial or municipal waste incineration and contains various metal elements. In this work, we focus on the waste-to-resource conversion of one fly ash which is generated from the incineration of petroleum coke gasification waste. The leaching behaviors and waste conversion of this fly ash to value-added products under different treatments were investigated. The majority of the identified elements in leachate demonstrated different leaching patterns as the species of leached element from fly ashes depend on the chemical properties of leaching agents. Moreover, A pathway is developed to harvest toxic vanadium from this fly ash, and the vanadium-containing leachate can be further converted into electrolyte for vanadium redox flow battery (VRFB). The vanadium electrolyte was synthesized by using fly ash leachate as the resource materials in two different ways afterwards: reducing vanadium in the leachate directly (electrolyte from leachate) and synthesizing V2O5 from leachate as the intermediate product (electrolyte from leachate-derived V2O5). The electrochemical behavior and performance of these electrolytes were analyzed to investigate the feasibility of these approaches. The measurement of electrochemical performance proves that the electrolyte from leachate-derived V2O5 is comparable to the standard electrolyte in terms of columbic efficiency (CE), energy efficiency (EE) and stability. Based on experimental results, our research provides a potential solution for the establishment of vanadium flow battery plant. Cost-benefit analysis proves that the payback period of electrolyte synthesized from alkaline leachate and leachate-derived V2O5 is 2.1 years and 1.0 year, respectively.

Redox-Mediated Ambient Electrolytic Nitrogen Reduction for Hydrazine and Ammonia Generation.

This work presents a redox-mediated electrolytic nitrogen reduction reaction (RM-eNRR) using polyoxometalate (POM) as the electron and proton carrier which frees the TiO2 -based catalyst from the electrode and shifts the reduction of nitrogen to a reactor tank. The RM-eNRR process has achieved an ammonium production yield of 25.1 µg h-1 or 5.0 µg h-1 cm-2 at an ammonium concentration of 6.7 ppm. With high catalyst loading, 61.0 ppm ammonium was accumulated in the electrolyte upon continuous operation, which is the highest concentration detected for ambient eNRR so far. The mechanism underlying the RM-eNRR was scrutinized both experimentally and computationally to delineate the POM-mediated charge transfer and hydrogenation process of nitrogen molecule on the catalyst. RM-eNRR is expected to provide an implementable solution to overcome the limitations in the conventional eNRR process.