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1.
Adv Mater ; : e1904249, 2019 Dec 26.
Artigo em Inglês | MEDLINE | ID: mdl-31880031

RESUMO

The development of highly efficient photocatalytic systems with rapid photogenerated charge separation and high surface catalytic activity is highly desirable for the storage and conversion of solar energy, yet remains a grand challenge. Herein, a conceptionally new form of atomically dispersed Co-P3 species on CdS nanorods (CoPSA-CdS) is designed and synthesized for achieving unprecedented photocatalytic activity for the dehydrogenation of formic acid (FA) to hydrogen. X-ray absorption near edge structure, X-ray photoelectron spectroscopy, and time-resolved photoluminescence results confirm that the Co-P3 species have a unique electron-rich feature, greatly improving the efficiency of photogenerated charge separation through an interface charge effect. The in situ attenuated total reflection infrared spectra reveal that the Co-P3 species can achieve much better dissociation adsorption of FA and activation of CH bonds than traditional sulfur-coordinated Co single atom-loaded CdS nanorods (CoSSA-CdS). These two new features make CoPSA-CdS exhibit the unprecedented 50-fold higher activity in the photocatalytic dehydrogenation of FA than CoSSA-CdS, and also much better activity than the Ru-, Rh-, Pd-, or Pt-loaded CdS. Besides, CoPSA-CdS also shows the highest mass activity (34309 mmol gCo -1 h-1 ) of Co reported to date. First-principles simulation reveals that the Co-P3 species herein can form an active PHCOO intermediate for enhancing the rate-determining dissociation adsorption of FA.

2.
Angew Chem Int Ed Engl ; 58(40): 14184-14188, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31365167

RESUMO

Noble metal single atoms coordinated with highly electronegative atoms, especially N and O, often suffer from an electron-deficient state or poor stability, greatly limiting their wide application in the field of catalysis. Herein we demonstrate a new PH3 -promoted strategy for the effective transformation of noble metal nanoparticles (MNPs, M=Ru, Rh, Pd) at a low temperature (400 °C) into a class of thermally stabilized phosphorus-coordinated metal single atoms (MPSAs) on g-C3 N4 nanosheets via the strong Lewis acid-base interaction between PH3 and the noble metal. Experimental work along with theoretical simulations confirm that the obtained Pd single atoms supported on g-C3 N4 nanosheets exist in the form of PdP2 with a novel electron-rich feature, conceptionally different from the well-known single atoms with an electron-deficient state. As a result of this new electronic property, PdP2 -loaded g-C3 N4 nanosheets exhibit 4 times higher photocatalytic H2 production activity than the state-of-art N-coordinated PdSAs supported on g-C3 N4 nanosheets. This enhanced photocatalytic activity of phosphorus-coordinated metal single atoms with an electron-rich state was quite general, and also observed for other active noble metal single atom catalysts, such as Ru and Rh.

3.
Chem Sci ; 10(23): 5898-5905, 2019 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-31360394

RESUMO

Sub-nanometer noble metal catalysts, especially single atom (SA), are a new class of catalytic materials for boosting catalysis and possess unique catalytic properties and high atomic utilization efficiency. Exploring the interaction between two neighboring atom monomers has great potential to further improve the performance of SA catalysts and deepen the understanding on the catalytic mechanism of heterogeneous catalysis at the atomic level. Herein, we demonstrate that the synergetic effect between neighboring Pt and Ru monomers supported on N vacancy-rich g-C3N4 promotes the catalytic CO oxidation. The experimental observation and theoretical simulation reveal that the N vacancy in the g-C3N4 structure builds an optimized triangular sub-nanometer cavity for stabilizing the neighboring Pt-Ru monomers by forming Pt-C and Ru-N bonds. The mechanistic studies based on the in situ IR spectrum and theoretical simulation confirm that the neighboring Pt-Ru monomers possess a higher performance for optimizing O2 activation than Ru-Ru/Pt-Pt monomers or isolated Ru/Pt atoms by balancing the energy evolution of reaction steps in the catalytic CO oxidation. The discovery of the synergetic effect between neighboring monomers may create a new path for manipulating the catalytic properties of SA catalysts.

4.
Adv Mater ; 31(15): e1805833, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30803065

RESUMO

The development of new electrocatalysts with high activity and durability for alcohol oxidation is an emerging need of direct alcohol fuel cells. However, the commonly used Pt-based catalysts still exhibit drawbacks including limited catalytic activity, high overpotential, and severe CO poisoning. Here a general approach is reported for preparing ultrathin PtNiM (M = Rh, Os, and Ir) nanowires (NWs) with excellent anti-CO-poisoning ability and high activity. Owing to their superior nanostructure and optimal electronic interaction, the ultrathin PtNiM NWs show enhanced electrocatalytic performance for both methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR). The optimal PtNiRh NWs show mass activity of 1.72 A mg-1 and specific activity of 2.49 mA cm-2 for MOR, which are 3.17 and 2.79 times higher than those of Pt/C. In particular, the onset potentials of PtNiRh NWs for MOR and EOR shift down by about 65 and 85 mV compared with those of Pt/C. Density functional theory calculations further verify their high antipoison properties for MOR and EOR from both an electronic and energetic perspective. Facilitated by the introduction of Rh and Ni, the stable pinning of the Pt 5d band associated with electron-rich and depletion centers solves the dilemma between reactivity and anti-CO poisoning.

5.
ACS Nano ; 13(2): 2167-2175, 2019 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-30689350

RESUMO

Despite its very high capacity (4200 mAh g-1), the widespread application of the silicon anode is still hampered by severe volume changes (up to 300%) during cycling, which results in electrical contact loss and thus dramatic capacity fading with poor cycle life. To address this challenge, 3D advanced Mxene/Si-based superstructures including MXene matrix, silicon, SiO x layer, and nitrogen-doped carbon (MXene/Si@SiO x@C) in a layer-by-layer manner were rationally designed and fabricated for boosting lithium-ion batteries (LIBs). The MXene/Si@SiO x@C anode takes the advantages of high Li+ ion capacity offered by Si, mechanical stability by the synergistic effect of SiO x, MXene, and N-doped carbon coating, and excellent structural stability by forming a strong Ti-N bond among the layers. Such an interesting superstructure boosts the lithium storage performance (390 mAh g-1 with 99.9% Coulombic efficiency and 76.4% capacity retention after 1000 cycles at 10 C) and effectively suppresses electrode swelling only to 12% with no noticeable fracture or pulverization after long-term cycling. Furthermore, a soft package full LIB with MXene/Si@SiO x@C anode and Li[Ni0.6Co0.2Mn0.2]O2 (NCM622) cathode was demonstrated, which delivers a stable capacity of 171 mAh g-1 at 0.2 C, a promising energy density of 485 Wh kg-1 based on positive active material, as well as good cycling stability for 200 cycles even after bending. The present MXene/Si@SiO x@C becomes among the best Si-based anode materials for LIBs.

6.
Adv Mater ; 31(5): e1807226, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30516862

RESUMO

Inspired by natural photosynthesis, the design of new Z-scheme photocatalytic systems is very promising for boosting the photocatalytic performance of H2 production and CO2 reduction; however, until now, the direct synthesis of efficient Z-scheme photocatalysts remains a grand challenge. Herein, it is demonstrated that an interesting Z-scheme photocatalyst can be constructed by coupling In2 O3 and ZnIn2 Se4 semiconductors based on theoretical calculations. Experimentally, a class of ultrathin In2 O3 -ZnIn2 Se4 (denoted as In2 O3 -ZISe) spontaneous Z-scheme nanosheet photocatalysts for greatly enhancing photocatalytic H2 production is made. Furthermore, Mo atoms are incorporated in the Z-scheme In2 O3 -ZISe nanosheet photocatalyst by forming the MoSe bond, confirmed by X-ray photoelectron spectroscopy, in which the formed MoSe2 works as cocatalyst of the Z-scheme photocatalyst. As a consequence, such a unique structure of In2 O3 -ZISe-Mo makes it exhibit 21.7 and 232.6 times higher photocatalytic H2 evolution activity than those of In2 O3 -ZnIn2 Se4 and In2 O3 nanosheets, respectively. Moreover, In2 O3 -ZISe-Mo is also very stable for photocatalytic H2 production by showing almost no activity decay for 16 h test. Ultraviolet-visible diffuse reflectance spectra, photoluminescence spectroscopy, transient photocurrent spectra, and electrochemical impedance spectroscopy reveal that the enhanced photocatalytic performance of In2 O3 -ZISe-Mo is mainly attributed to its widened photoresponse range and effective carrier separation because of its special structure.

7.
Adv Mater ; 31(2): e1805541, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30417441

RESUMO

Designing non-precious-metal catalysts with comparable mass activity to state-of-the-art noble-metal catalysts for the hydrogen evolution reaction (HER) in alkaline solution still remains a significant challenge. Herein a new strongly coupled nickel-cobalt nitrides/carbon complex nanocage (NiCoNzocage) is rationally designed via chemical etching of ZIF-67 nanocubes with Ni(NO3 )2 under sonication at room temperature, following nitridation. The as-prepared strongly coupled NiCoN/C nanocages exhibit a mass activity of 0.204 mA µg-1 at an overpotential of 200 mV for the HER in alkaline solution, which is comparable to that of commercial Pt/C (0.451 mA µg-1 ). The strongly coupled NiCoN/C nanocages also possess superior stability for the HER with negligible current loss under the overpotentials of 200 mV for 10 h. Density functional theory (DFT) calculations reveal that the excellent HER performance under alkaline condition arises from the robust Co2+ →Co0 transformation achieved by strong (Ni, Co)N-bonding-induced efficient d-p-d coupled electron transfer, which is a key for optimal initial water adsorption and splitting. The high degree of amorphization urges the C-sites to be an electron-pushing bath to promote the inter-layer/sites electron-transfer with loss of the orbital-selection-forbidden-rule, which uniformly boosts the surface catalytic activities up to a high level independent of the individual surface active sites.

8.
Chemistry ; 25(1): 189-194, 2019 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-30351453

RESUMO

Converting renewable biomass and their derivatives into chemicals and fuels has received much attention to reduce the dependence on fossil resources. Photocatalytic ethanol dehydrogenation-acetalization to prepare value-added 1,1-diethoxyethane and H2 was achieved over non-precious metal CdS/Ni-MoS2 catalyst under visible light. The system displays an excellent production rate and high selectivity of 1,1-diethoxyethane, 52.1 mmol g-1 h-1 and 99.2 %, respectively. In-situ electron spin resonance, photoluminescence spectroscopy and transient photocurrent responses were conducted to investigate the mechanism. This study provides a promising strategy for a green application of bioethanol.

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