The urea oxidation reaction (UOR) has gained significant attention as an alternative to the oxygen evolution reaction (OER) for reducing energy consumption during simultaneous hydrogen production and degradation of urea. However, developing efficient electrocatalysts for UOR remains challenging due to the sluggish intrinsic kinetics involved in the six-electron process. In this study, we report the use of carbon-dot-modified ultrathin Ni3S2 nanosheets on nickel foam (Ni3S2–CDs@NF) with a quasi-parallel structure for urea-assisted electrocatalytic hydrogen evolution reaction (HER). The zero-dimensional/two-dimensional (0D/2D) Ni3S2–CDs@NF catalyst exhibit high bifunctional catalytic activities with a potential of 88 mV for HER and 1.35 V (vs RHE) for UOR at a current density of 10 mA cm–2. By incorporating Ni3S2–CDs@NF into a symmetrical electrolytic cell, low cell voltages of 1.67 and 1.81 V were acquired at the current densities of 50 and 100 mA cm–2 for HER||UOR, which are 110 and 280 mV lower than those of the nonreal HER||OER system, respectively. Further electrochemical tests demonstrated that the 0D/2D heterointerface between CDs and Ni3S2 maximized the exposure of surface-active sites while enhancing the electron transfer rates and reaction kinetics. This study not only offers insights into efficient carbon-dot-based electrocatalysts for urea electrolysis, but also holds significant potential for applications in electrochemical energy conversion and wastewater treatment.
Monolithic 3D graphene frameworks (GFs) electrode materials have exhibited the great potential for energy storage devices. However, most approaches for fabricating 3D GF require expensive and sophisticated drying techniques, and the current achieved 3D GF electrodes usually hold a relatively low mass loadings of the active materials with low areal capacity, which is not satisfactory for practical application. Herein, a convenient, economic, and scalable drying approach is developed to fabricate 3D holey GFs (HGFs) by a vacuum‐induced drying (VID) process for the first time. This binder‐free 3D HGF electrode with high mass loading can obtain extraordinary electrochemical performance for lithium‐ion batteries (LIBs) due to the 3D holey graphene network owning a highly interconnected hierarchical porous structure for fast charge and ion transport. The HGF electrode with high mass loading of 4 mg cm −2 exhibits superior rate performance and delivers an areal capacity as high as 5 mAh cm −2 under the current density of 8 mA cm −2 even after 2000 cycles, considerably outperforming those of state‐of‐the‐art commercial anodes and some representative anodes in other studies. This facile drying approach and robust realization of high areal capacity represent a critical step for 3D graphene‐based electrode materials toward practical electrochemical energy storage devices.
Iron-based hexacyanoferrate (Fe-HCF) are promising cathode materials for sodium-ion batteries (SIBs) due to their unique open-channel structure that facilitates fast ion transport and framework stability. However, practical implementation of SIBs has been hindered by low initial Coulombic efficiency (ICE), poor rate performance, and short lifespan. Herein, we report a coordination engineering to synthesize sodium-rich Fe-HCF as cathodes for SIBs through a uniquely designed 10-kg-scale chemical reactor. Our study systematically investigated the relationship between coordination surroundings and the electrochemical behavior. Building on this understanding, the cathode delivered a reversible capacity of 99.3 mAh g
Novel ozone sensors based on In/sub 2/O/sub 3/ thin films on sapphire substrates with interdigitated comb structures have been prepared from indium isopropoxide solutions by the sol-gel process. Highly sensitive films have been obtained by using aged solutions. The annealing temperature was 500/spl deg/C. Compared with earlier thin film devices, the advantages of these sensors include significantly higher ozone sensitivity (as large as 6 at 45 ppb), lower working temperature (below 200/spl deg/C) and low production cost.
A uniform carbon dot-decorated TiO2 nanotube array composite heterojunction with full spectrum wavelength light activation was fabricated via a facile electrochemical strategy for efficient dye degradation and overall water splitting.
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