Water splitting is a critical process for the production of green hydrogen, contributing to the advancement of a circular economy. However, the application of water splitting devices on a large scale is primarily impeded by the sluggish oxygen evolution reaction (OER) at the anode. Thus, developing and designing efficient OER catalysts is a significant target. NiFe-based catalysts are extensively researched as excellent OER electrocatalysts due to their affordability, abundant reserves, and intrinsic activities. However, they still suffer from long-term stability challenges. To date, few systematic strategies for improving OER durability have been reported. In this review, various advanced NiFe-based catalysts are introduced. Moreover, the OER stability challenges of NiFe-based electrocatalysts in alkaline media, including iron segregation, structural degradation, and peeling from the substrate are summarized. More importantly, strategies to enhance OER stability are highlighted and opportunities are discussed to facilitate future stability studies for alkaline water electrolysis. This review presents a design strategy for NiFe-based electrocatalysts and anion exchange membrane (AEM) electrolyzers to overcome stability challenges in OER, which also emphasizes the importance of long-term stability in alkaline media and its significance for achieving large-scale commercialization.
Silicon (Si) anodes, known for their high capacity, confront obstacles such as volume expansion, the solid-electrolyte interface (SEI) formation, and limited cyclability, driving ongoing research for innovative solutions to enhance their performance in next-generation lithium-ion batteries (LIBs). This comprehensive review explores the forefront of one-dimensional (1D) Si/carbon anodes for high-performance LIBs. This review delves into cutting-edge strategies for fabricating 1D Si/carbon structures, such as nanowires, nanotubes, and nanofibers, highlighting their advantages in mitigating volume expansion, enhancing electron/ion transport, and bolstering cycling stability. The review showcases remarkable achievements in 1D Si/carbon anode performance, including exceptional capacity retention, high-rate capability, and prolonged cycle life. Challenges regarding scalability, cost-effectiveness, and long-term stability are addressed, providing insights into the path to commercialization. Additionally, future directions and potential breakthroughs are outlined, guiding researchers and industries toward harnessing the potential of 1D Si/ carbon anodes in revolutionizing energy storage.
Zinc bromine flow batteries (ZBFBs) are well suited for stationary energy storage due to their attractive features of high energy density and low cost. Nevertheless, the ZBFBs suffer from low power density and limited efficiency owing to the relatively severe polarization of the Br2/Br− redox couple. Herein, a three-dimensional (3D) hierarchical composite electrode based on core-shell Ni/NiO heterostructures anchored on graphite felt (Ni/NiO@GF) is designed to promote the kinetics of the Br2/Br− couple, so as to improve the power density and efficiency of the ZBFB. In this design, the highly conductive carbon felt and Ni cores provide a composite electrode with a 3D electron transporting framework to guarantee excellent electronic conductivity, while the NiO shells possess great absorption ability to Br2 and brilliant catalytic activity for the Br2/Br− redox reaction to reduce the electrochemical polarization. As a result, an enhanced ZBFB with Ni/NiO@GF electrode shows an outstanding energy efficiency of 86% at 20mA cm−2 and can be operated at a current density of up to 160 mA cm−2 with a respectable energy efficiency of 67%. These results exhibit a promising strategy to fabricate catalytic electrodes for high-performance ZBFBs.
We successfully synthesized a series of O3-type NaNi1/3Fe1/3Mn1/3−xZrxO2 (x=0, 0.01, 0.02, 0.04) cathode materials by the solid-state reaction method. Energy dispersion spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy results confirmed the successful incorporation of Zr elements into the lattice to substitute Mn. Due to the introduction of Zr4+, the crystal structure modulation of O3-NaNi1/3Fe1/3Mn1/3O2 has been realized. By increasing the Zr4+ content, the width of the sodium diffusion layer expands, thereby facilitating the diffusion of sodium ions. Consequently, the material exhibits a remarkable enhancement in high-rate capability. At the same time, increasing the Zr4+ content results in a notable decrease in both the average bond length of TM−O and the thickness of the TMO6 octahedron in the transition metal layer, resulting in a significant improvement in the cycling performance and structural stability of the cathode material. Additionally, the in-situ XRD results demonstrate that the optimized cathode composition of O3-NaNi1/3Fe1/3Mn1/3-0.02Zr0.02O2 (NFMZ2) undergoes a reversible phase transition of O3→O3+ P3→P3→ O3 + P3→O3 during the charge-discharge process.
Carbon quantum dots (CQDs) have emerged as prominent contenders in the realm of luminescent nanomaterials over the past decade owing to their tunable optical properties, robust photostability, versatile surface functionalization and doping potential, low toxicity, and straightforward synthesis utilizing environmentally friendly precursors. In this review, we commence with a concise introduction, presenting both top-down and bottom-up strategies for the eco-friendly synthesis of CQDs. Subsequently, we delve into a comprehensive examination of CQDs' structure and optical characteristics, encompassing their ultraviolet-visible absorption properties, surface confinement effects, and surface state emissions contributing to room-temperature photoluminescence (PL). This review proceeds to elucidate recent advancements in modification strategies for CQDs, specifically focusing on surface oxidation, passivation, and the incorporation of heteroatoms. These strategies serve to afford control over the physicochemical properties, facilitating the enhancement of PL through the decoration of highly visible-responsive CQDs. This enhancement is achieved by suppressing the nonradiative recombination of electron-hole pairs, enabling red/blue shifts in CQDs for the generation of a full-color emission spectrum, and regulating the band-gap and surface states to broaden the photoabsorption range. Finally, we offer an overview of the most recent developments in the applications of fluorescent CQDs, emphasizing their utility in biomedicine, fluorescent sensors, lighting, and displays, as well as photocatalysis.
The electrochemical alcohol oxidation reaction (AOR) is pivotal for the development of sustainable energy. The complete oxidation of alcohols has attracted extensive attention as a vital process in fuel cells. Moreover, as an alternative reaction to the oxygen evolution reaction, the selective oxidation of alcohols emerges as an effective means to lower the energy expenditure associated with electrolytic hydrogen production while yielding high-value products. Nonprecious metal materials have been widely applied in the selective oxidation catalysis of alcohols due to their cost-effectiveness and excellent durability. In recent years, leveraging the advantages of nonprecious metal materials in electrocatalytic AOR, researchers have delved into catalytic mechanisms and various efficient catalysts have been fabricated and evaluated. This review provides an overview of the current advancements in the electrocatalytic selective oxidation of diverse alcohols and the catalytic systems centered around nonprecious metal materials. It systematically summarizes the shared traits and distinctions in catalytic reaction characteristics across various systems, thereby laying the theoretical foundation for developing novel catalyst systems that are efficient, stable, and highly selective. This review will facilitate the utilization of nonprecious metal catalysts further toward the electrocatalytic oxidation of alcohols.
With the expansion of the global population, the energy shortage is becoming increasingly acute. Phase change materials (PCMs) are considered green and efficient mediums for thermal energy storage, but the leakage problem caused by volume instability during phase change limits their application. Encapsulating PCMs with supporting materials can effectively avoid leakage, but most supporting materials are expensive and consume huge of natural resources. Carbon materials, which are rich and renewable resources, can be used as economical and environmentally friendly supporting skeletons to prepare form-stable PCMs. Although many researchers have begun to use recyclable materials especially various derivatives of carbon as supporting skeletons to prepare form-stable PCMs, the preparation methods, thermophysical properties and applications of form-stable PCMs with recyclable skeletons have rarely been systematically summarized yet. Form-stable PCMs with a recyclable skeleton can be used as green and efficient thermal storage materials due to their high heat storage capacity and good thermophysical stability after 2000 thermal cycles. This review investigates the effects of recyclable skeletons on the thermophysical properties including phase change temperature, latent heat, thermal conductivity, supercooling, and thermal cycling reliability. Four major kinds of recyclable skeletons are focused on: biomass, biochar, industrial by-products as well as waste incineration ash. Additionally, the application scales of form-stable PCMs with recyclable skeletons are explicated in depth. Moreover, the main challenges confronted by form-stable PCMs with recyclable skeletons are discussed, and future research trends are proposed. This article provides a systematic review of the form-stable PCMs with recyclable skeletons, giving significant guidance for further reducing carbon emissions and promoting the development of sustainable energy.