Used as high-performance electrodes, both structural and compositional alterations of carbon materials play very important roles in energy conversion/storage devices. Especially in supercapacitors, hierarchical pores and heteroatom doping in carbon materials are indispensable. Here the rambutan-like hierarchically porous carbon microspheres (PCMs) have been constructed via a hydrothermal treatment, followed by carbonization/activation. The hierarchically porous microstructure is composed of three-dimensional porous carbon networks, which give rise to a large surface area. Moreover, N and O functional groups are introduced in the as-prepared samples, which could generate the extra pseudocapacitance. Benefitting from the interconnected hierarchical and open structure, PCM exhibits outstanding capacitive performance, for example, superior specific capacitance and rate capability (397 and 288 F g −1 at 0.5 and 20 A g −1 , respectively), as well as long cycling stability (about 95% capacitance retention after 10,000 cycles). These encouraging results may pave an efficient way to fabricate advanced supercapacitors in the future.
Catalysts with high activity play an indispensable role in ammonia‐borane (AB) hydrolysis for hydrogen production. Supported catalysts are always used because proper support can effectively prevent metal particle agglomeration. In addition, the interaction between support and metal species can further enhance the catalytic activity. Herein, cobalt‐embedded porous carbon with polyhedral structure (CoPCP) is successfully synthesized by one‐step carbonization of a core‐shell structured ZIF‐8@ZIF‐67 composite. As support, Ru nanoparticles are loaded on CoPCP by in situ reduction to obtain Ru/CoPCP catalysts with a special hollow structure, effectively preventing Ru nanoparticles from agglomeration. Moreover, the existence of synergistic effect between Co metal and Ru nanoparticles in Ru/CoPCP catalyst is confirmed by a series of well‐designed control experiments. Both these factors endow the Ru/CoPCP catalyst with high activity and decent stability toward AB hydrolysis. A low activation energy (Ea = 31.25 kJ mol–1) and a high catalytic performance (turnover frequency = 243.4 molH2 molRu–1 min–1) are simultaneously achieved for Ru1/CoPCP‐1000 even with a low amount of Ru (1.88 wt%). This work represents a promising method to prepare the high‐activity catalysts with low content of noble metals for diverse applications in heterogeneous catalysis.
Fe-N-C electrocatalysts with abundant Fe-Nx active sites are considered to be one of the most promising nonprecious metal catalysts (NPMCs) toward oxygen reduction reaction (ORR) in metal-air batteries and hydrogen-oxygen...
Uniform Al 2 O 3 :Eu 3+ samples were successfully fabricated via a hydrothermal method and subsequent thermal decomposition of Eu 3+ -doped precursors. The sample characterisations were carried out by means of X-ray diffraction (XRD), scanning electron microscope (SEM) and photoluminescence spectra. XRD results revealed Eu 3+ -doped samples were a pure γ-Al 2 O 3 phase after being calcined at 1173 K. SEM results showed that these Eu 3+ -doped Al 2 O 3 samples were stalk-like, with an average length of 1.5 μm. Upon excitation at 394 nm, the orange-red emission bands, having wavelengths longer than 580 nm, were to be from 5 D 0 → 7 F J (J = 1, 2) transitions. The asymmetry ratio of ( 5 D 0 → 7 F 2 )/( 5 D 0 → 7 F 1 ) intensity is about 0.54, 2. 76, 3.29, 2.86, 3.36, 3.13 for Eu 3+ concentrations of 0.1, 0.4, 0.7, 1.0, 1.5 and 2.0 mol-%, respectively. The optimal doping concentration of Eu 3+ ions in Al 2 O 3 is 1.5 mol-%. According to Dexter's theory, the critical distance between Eu 3+ ions for energy transfer was determined to be 14 Å.
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