• Energy Research

The Fe/FeCl2-Graphite molten salt battery is a promising technology for large-scale energy storage, offering a long lifespan, a low operating temperature (<200 °C), and cost efficiency. However, its practical applications are hindered by the lack of a scalable preparation approach and insufficient redox stability in the Fe/FeCl2 electrode. Our study introduces an electrochemical anodic electrolysis (EAE) strategy, employing the anodic process (Fe → Fe2+) in an Al|AlCl3/NaCl/LiCl|Fe electrolysis system for the Fe/Fe2+ negative electrode in the Fe/FeCl2-Graphite battery. The EAE strategy forms an oxidized film, preventing incipient dissolution in the electrolyte and addressing redox stability issues with FeCl2 as the active substance. The Fe/Fe2+ negative electrode prepared by the EAE strategy exhibits a stabilized capacity of 0.72 mAh/cm2 after 7000 cycles at 5 mA/cm2, with a lower polarization level (∼29 mV) compared to FeCl2 as the active component. The flexibility of the EAE strategy is validated in both galvanostatic and potentiostatic processes, with a discharge capacity of 14 mAh after 1000 cycles, a capacity retention rate of 85%, and a Coulombic efficiency of 98% in the potentiostatic anodic electrolysis Fe/Fe2+ electrode. The scalability and reliability of the EAE strategy are further demonstrated in capacity-expanded Fe/FeCl2-Graphite batteries, reaching a discharge capacity of 155.1 mAh after 1000 cycles at 130 mA, with a capacity retention rate of 94%. For the first time, we showcased an EAE approach capable of producing Fe/Fe2+ electrodes at a rate of about 68.6 m2 per day. Additionally, we successfully assembled an Fe/FeCl2-Graphite battery at about a 0.42 ampere-hour level, paving the way for the scalable application of Fe/FeCl2-Graphite batteries.

Amine-based scrubbing technique is recognized as a promising method of capturing CO2 to alleviate climate change. However, the less stability and poor acidity of solid acid catalysts (SACs) limit their potential to further improve amine regeneration activity and reduce the energy penalty. To address these challenges, here, we introduce two-dimensional (2D) cobalt-nitrogen-doped carbon nanoflakes (Co-N-C NSs) driven by a layered metal-organic framework that work as SACs. The designed 2D Co-N-C SACs can exhibit promising stability, superhydrophilic surface, and acidity. Such 2D structure also contains well-confined Co-N4 Lewis acid sites and -OH Brønsted acid sites to have a synergetic effect on C-N bond disruption and significantly increase CO2 desorption rate by 281% and reduce the reaction temperatures to 88 °C, minimizing water evaporation by 20.3% and subsequent regeneration energy penalty by 71.7% compared to the noncatalysis.

Countries around the world are actively promoting the low-carbon transformation of the energy system, and renewable energy represented by solar photovoltaic (PV) power generation will occupy a greater proportion of the power system. The power of PV power generation is characterized by randomness and volatility, so an energy storage system (ESS) is needed for smooth control of fluctuating power to improve the quality of electric energy and the stability of the system. First of all, through the comparative analysis of various energy storage technologies, this paper finds that the battery-supercapacitor hybrid energy storage system (HESS) has both steady-state and dynamic response capabilities. Secondly, the power smoothing control strategy comprises centralized control strategies and distributed control strategies, corresponding control algorithms based on filter and optimization, and droop control strategy, respectively. This paper introduces them in turn and analyzes their advantages and disadvantages. Finally, according to the characteristics of the two control strategies, the analysis of the applicable scenarios is given, and it can guide future applications.

Thermocells can sustainably generate electricity from waste heat temperature gradients. This study investigates numerous fundamental aspects of thermocells, and how to explain and model such aspects.

Electrochemical energy storage (EES) devices with high‐power density such as capacitors, supercapacitors, and hybrid ion capacitors arouse intensive research passion. Recently, there are many review articles reporting the materials and structural design of the electrode and electrolyte for supercapacitors and hybrid capacitors (HCs), though these reviews always focus on individual supercapacitors or single HCs. Herein, the conventional capacitor, supercapacitor, and hybrid ion capacitor are incorporated, as the detailed description of conventional capacitors is very fundamental and necessary for the better understanding and development of supercapacitors and hybrid ion capacitors, which are often ignored. Therefore, herein, the fundamentals and recent advances of conventional capacitors, supercapacitors, and emerging hybrid ion capacitors are comprehensively and systematically summarized in terms of history, mechanisms, electrode materials, existing challenges, and perspectives. At the same time, it is believed that a comprehensive and fundamental understanding for capacitor‐related EES devices is provided in the review and has a great guiding role for future development.

Summary: The majority of usable energy generated by humanity is lost as waste heat, but thermogalvanic systems (or thermocells) can address this problem by converting low-grade waste heat directly into electricity using redox chemistry. The concentration of the redox couple is a critical parameter; almost invariably, higher concentrations result in more power. This study exploits the simple synergy between Na+ and K+ counter ions to achieve—to the best of our knowledge—the most concentrated stable aqueous ferricyanide/ferrocyanide thermocell to date, at 1.6 m [Fe(CN)6]3−/4−. Despite increasing the concentration by 400% relative to the standard K3/K4[Fe(CN)6] electrolyte (0.4 m), electrical power production increased only 166%. Pushing the system from conventional salt-in-water electrolytes into the quasi-stable water-in-salt region (up to 2.4 m) resulted in a decrease in power. Detailed characterization highlighted the various physicochemical hurdles introduced by these extremely concentrated electrolytes; the identified issues have direct relevance to other energy systems also seeking to use the highest possible concentration.

Active sites play a pivotal role in photo/electrocatalysis, particularly in the transition from fossil fuels to clean, efficient and renewable energy sources.

A versatile on-chip electrochemical testing platform enables simultaneous catalyst screening and in situ analysis of chemical composition and morphological evolution of reaction products in Li–CO2 batteries, further guiding practical applications.