The development of highly active and stable earth-abundant catalysts to reduce or eliminate the reliance on noble-metal based ones in green and sustainable (electro)chemical processes is nowadays of great interest. Here, N-, O-, and S-tridoped carbon-encapsulated Co 9 S 8 (Co 9 S 8 @NOSC) nanomaterials are synthesized via simple pyrolysis of S-and Co(II)-containing polypyrrole solid precursors, and the materials are proven to serve as noble metal-free bifunctional electrocatalysts for water splitting in alkaline medium. The nanomaterials exhibit remarkable catalytic performances for oxygen evolution reaction in basic electrolyte, with small overpotentials, high anodic current densities, low Tafel slopes as well as very high (nearly 100%) Faradic efficiencies. Moreover, the materials are found to efficiently electrocatalyze hydrogen evolution reaction in acidic as well as basic solutions, showing high activity in both cases and maintaining good stability in alkaline medium. A two-electrode electrolyzer assembled using the material synthesized at 900 °C (Co 9 S 8 @NOSC-900) as an electrocatalyst at both electrodes gives current densities of 10 and 20 mA cm −2 at potentials of 1.60 and 1.74 V, respectively. The excellent electrocatalytic activity exhibited by the materials is proposed to be mainly due to the synergistic effects between the Co 9 S 8 nanoparticles cores and the heteroatom-doped carbon shells in the materials.

Replacing rare and expensive metal catalysts with inexpensive and earth-abundant ones is currently among the major goals of sustainable chemistry. Herein we report the synthesis of N-, O-, and S-tridoped, polypyrrole-derived nanoporous carbons (NOSCs) that can serve as metal-free, selective electrocatalysts and catalysts for oxygen reduction reaction (ORR) and alcohol oxidation reaction (AOR), respectively. The NOSCs are synthesized via polymerization of pyrrole using (NH4)2S2O8 as oxidant and colloidal silica nanoparticles as templates, followed by carbonization of the resulting S-containing polypyrrole/silica composite materials and then removal of the silica templates. The NOSCs exhibit good catalytic activity toward ORR with low onset potential and low Tafel slope, along with different electron-transfer numbers, or in other words, different ratios H2O/H2O2 as products, depending on the relative amount of colloidal silica used as templates. The NOSCs also effectively catalyze AOR at relatively low temperature, giving good conversions and high selectivity.

We demonstrate that polypyrrole-derived nitrogen and oxygen co-doped mesoporous carbons can serve as efficient, metal-free electrocatalysts for hydrazine oxidation reaction, with low overpotential and high current density. The materials' structures and the nature and type of their included dopants, which can be controlled by varying the synthetic conditions, can affect the electrocatalytic properties of the materials.

Energy migration (energy transfer among identical luminescence centers) is always thought to be related to the concentration quenching in luminescence materials. However, the novel Eu 3+ -doped Ba 6 Gd 2 Ti 4 O 17 phosphor seems to be an exception. In the series of Ba 6 Gd 2(1−x) Ti 4 O 17 :xEu 3+ (x = 0.1, 0.3, 0.5, 0.7, and 0.9) phosphors prepared and investigated, no concentration quenching is found. Detailed investigations of the crystal structure and the luminescence properties of Ba 6 Gd 2(1−x) Ti 4 O 17 :xEu 3+ reveal that the nonoccurrence of concentration quenching is related to the dimensional restriction of energy migration inside the crystal lattices. In Ba 6 Gd 2 Ti 4 O 17 , directly increasing the number of Eu 3+ ions to absorb as much excitation energy as possible allows to achieve a higher brightness. The highly Eu 3+ -doped Ba 6 Gd 2(1−x) Ti 4 O 17 :xEu 3+ (x = 0.9) sample can convert near-UV excitation into red light, whose Commission Internationale de l'Eclairage (CIE) coordinates are (0.64, 0.36) and the color purity can reach up to 94.4%. Moreover, warm white light with the CIE chromaticity coordinates of (0.39, 0.39), the correlated color temperature of 3756 K, and the color rendering index of 82.2 is successfully generated by fabricating this highly Eu 3+ -doped phosphor in a near-UV light-emitting diode chip together with the green YGAB:Tb 3+ and blue BAM:Eu 2+ phosphors. KEYWORDS: Eu 3+ -doped phosphor, Ba 6 Gd 2 Ti 4 O 17 host, nonconcentration quenching, energy migration, light-emitting diodes

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Eu ion can be effectively sensitized by Ce ion through an energy-transfer chain of Ce-(Tb) -Eu, which has contributed to the development of white light-emitting diodes (WLEDs) as it can favor more efficient red phosphors. However, simply serving for WLEDs as one of the multicomponents, the design of the Ce-(Tb) -Eu energy transfer is undoubtedly underused. Theoretically, white light can be achieved with extra blue and green emissions released from Ce and Tb. Herein, the design of the white light based on these three multicolor luminescence centers has been realized in GdBO. It is the first time that white light is generated via accurate controls on the Ce-(Tb) -Eu energy transfer in such a widely studied host material. Because the thermal quenching rates of blue, green, and red emissions from Ce, Tb, and Eu, respectively, are well-matched in the host, this novel white light exhibits superior color stability and potential application prospect.

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