Fabricating non-noble metal-based carbon air electrodes with highly efficient bifunctionality is big challenge owing to the sluggish kinetics of oxygen reduction/evolution reaction (ORR/OER). The efficient cathode catalyst is urgently needed to further improve the performance of rechargeable zinc-air batteries. Herein, an activation-doping assisted interface modification strategy is demonstrated based on freestanding integrated carbon composite (CoNiLDH@NPC) composed of wood-based N and P doped active carbon (NPC) and CoNi layer double hydroxides (CoNiLDH). In the light of its large specific surface area and unique defective structure, CoNiLDH@NPC with strong interface-coupling effect in 2D-3D micro-nanostructure exhibits outstanding bifunctionality. Such carbon composites show half-wave potential of 0.85 V for ORR, overpotential of 320 mV with current density of 10 mA cm−2 for OER, and ultra-low gap of 0.70 V. Furthermore, highly-ordered open channels of wood provide enormous space to form abundant triple-phase boundary for accelerating the catalytic process. Consequently, zinc-air batteries using CoNiLDH@NPC show high power density (aqueous: 263 mW cm−2, quasi-solid-state: 65.8 mW cm−2) and long-term stability (aqueous: 500 h, quasi-solid-state: 120 h). This integrated protocol opens a new avenue for the rational design of efficient freestanding air electrode from biomass resources.
Abstract Limited triple‐phase boundaries arising from the accumulation of solid discharge product(s) in solid‐state cathodes (SSCs) pose a challenge to high‐property solid‐state lithium‐oxygen batteries (SSLOBs). Light‐assisted SSLOBs have been gradually explored as an ingenious system; however, the fundamental mechanisms of the SSCs interface behavior remain unclear. Here, we discovered that light assistance can enhance the fast inner‐sphere charge transfer in SSCs and regulate the discharge products with spherical particles generated via the surface growth model. Moreover, the high photoelectron excitation and transportation capabilities of SSCs can retard cathodic catalytic decay by avoiding structural degradation of the cathode with a reduced charge voltage. The light‐induced SSLOBs exhibited excellent stability (170 cycles) with a low discharge–charge polarization overpotential (0.27 V). Furthermore, transparent SSLOBs with exceptional flexibility, mechanical stability, and multiform shapes were fabricated for theory‐to‐practical applications in sunlight‐induced batteries. Our study opens new opportunities for the introduction of solar energy into energy storage systems.
Nowadays, it is very challenging to develop a low-cost, highly active and stable bi-functional catalyst for accelerating oxygen reduction reaction (ORR) and oxygen evolution (OER) reaction during the charge and discharge process of zinc-air battery. Herein, we successfully design a novel bi-metal oxide hybrid catalyst (ZnCo 2 O 4 -CNT) by inserting Zn ions. Benefiting from the robust synergetic effects between porous ZnCo 2 O 4 and CNTs, the high conductivity and the unique nanostructure, the ZnCo 2 O 4 -CNT shows lots of accessible active sites and improved reactants and electrons transfer. As expected, the hybrid shows higher ORR and OER performances with larger limited diffusion current density (5.72 mA cm −2 ) and lower OER over-potential (0.49 V) than Pt/C and other ZnCo 2 O 4 -CNT samples. In addition, rechargeable zinc-air battery assembled with the bi-functional catalyst exhibits a high power density of 249.4 mW cm −2 , a strong discharge durability and charge-discharge stability of 240 cycles. Notably, the flexible zinc-air battery also shows good battery performances with high power density and good flexibility. Hence, exploiting efficient bi-functional catalytic materials with excellent ORR and OER performance and assembling flexible devices will improve the development of current zinc-air batteries battery industry.
Abstract Zero or negative emissions of carbon dioxide (CO 2 ) is the need of the times, as inexorable rising and alarming levels of CO 2 in the atmosphere lead to global warming and severe climate change. The electrochemical CO 2 reduction (eCO 2 R) to value‐added fuels and chemicals by using renewable electricity provides a cleaner and more sustainable route with economic benefits, in which the key is to develop clean and economical electrocatalysts. Carbon‐based catalyst materials possess desirable properties such as high offset potential for H 2 evolution and chemical stability at the negative applied potential. Although it is still challenging to achieve highly efficient carbon‐based catalysts, considerable efforts have been devoted to overcoming the low selectivity, activity, and stability. Here, we summarize and discuss the recent progress in carbon‐based metal‐free catalysts including carbon nanotubes, carbon nanofibers, carbon nanoribbons, graphene, carbon nitride, and diamonds with an emphasis on their activity, product selectivity, and stability. In addition, the key challenges and future potential approaches for efficient eCO 2 R to low carbon‐based fuels are highlighted. For a good understanding of the whole history of the development of eCO 2 R, the CO 2 reduction reactions, principles, and techniques including the role of electrolytes, electrochemical cell design and evaluation, product selectivity, and structural composition are also discussed. The metal/metal oxides decorated with carbon‐based electrocatalysts are also summarized. We aim to provide insights for further development of carbon‐based metal‐free electrocatalysts for CO 2 reduction from the perspective of both fundamental understanding and technological applications in the future.
Alkaline water electrolysis is one of most potential techniques for green hydrogen production, offering high energy conversion and storage. High current density and durability diaphragms are crucial for electrochemical performance. Here we have developed a high-performance composite diaphragm based on in-situ self-assemble of nickel-iron layered double hydroxides (NiFe-LDHs) loaded on Zirfon-type substrate, and at the same time catalytic NiFe-LDHs integrated the anode side for high-performance alkaline water electrolysis. By modulating the microstructure, a unique surficial feature with high surface free energy and super-hydrophilicity to address the issue of high ohmic resistance is established and achieves rapid OH−conduction and high catalytic oxygen evolution reaction (OER). Consequently, the prepared ZLDH-χ series diaphragm affords excellent application properties, with ZLDH-10 diaphragm an ultra-short wetting time of 0.23s and a reduction of 120 mV over-voltage in single electrolytic cell. Electrolyzer with ZLDH-10 diaphragm provides exceptional current density of 1400 mA cm-2 at 2.0 V in 80oC 30wt% KOH. Importantly, large-scale ZLDH-10 diaphragm with 37 × 37 cm2 can be readily made and reaches an unprecedented durability at 1000 mA cm-2@1.8 V over 240 hours. Both simple in-situ self-assemble approach and excellent performance of ZLDH-χ series diaphragm pave a new way for manufacturing diaphragm in advanced alkaline water electrolysis. A partial polarization method was first invented to figure out the contribution ratio for cell voltage reduction between NiFe-LDHs catalytic effect and hydrophilic improving effect.
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