查看更多>>摘要：The precise design and controllable manufacture of electrocatalysts for efficient oxygen reactions (OER and ORR) based on the abundant elements of the earth are urgently required but challenging task. In this study, a CoS2/Cu2S heterostructured composite (CoS2/Cu2S-NF) supported by the porous carbon nanofibers is synthesized as a high-efficiency oxygen reaction electrocatalyst. As indicated from in-situ characterization methods (infrared, Raman and XRD) integrated with the density functional theory results, the heterostructures exhibited by CoS2 and Cu2S could be regulated. The results show that the electron transfer/interaction between CoS2 and Cu2S in the heterojunction were regulated, as well as the electronic structures of Co and Cu sites. As impacted by the structural engineering and the electronic modulation, the activity was enhanced, and the performance of electrocatalytic oxygen reactions was improved, which exhibited the lowest potential difference for (Delta E = 0.73 V) compared with commercial electrocatalysts. The liquid ZAB in accordance with on CoS2/Cu2S-NF exhibited a stable charge and discharge capacity up to 590 h and a great power density reaching 260.60 mW cm(-2). Moreover, the flexible solid-state ZAB based on CoS2/Cu2S-NF exhibited a great competitive power density (92.06 mW cm(-2)), robust flexibility and an obvious integration. As compared with single metal sulfide-NF, the Density functional theory calculations (DFT) highlight the adsorption on CoS2/Cu2S-NF side surface in the heterojunction, which more specifically demonstrates the synergistic effect in the junction. This work presents a direction for designing heterostructured junctions as electrocatalyst and moreover its great application potential in rechargeable metal-solid batteries.
查看更多>>摘要：Yolk-shell nanohybrids have garnered increasing interests in many applications, such as in catalysis, energy, and molecular sensing. However, their intrinsic architectural limitations have led to insufficient synergistic effects and instability which are unfavorable for nanocatalysis. Designing a unique yolk-in-shell nanostructure where the "yolk" is embedded in the "shell" can overcome this challenge to boost nanocatalysis. Herein, an unprecedented Au@TiO2 yolk-in-shell nanocatalyst has been developed to dramatically improve the visible light photocatalysis. The as-designed Au@TiO2 nanohybrid displays an efficient hydrogen-production (95.6 mmol h(-1) g(-1), Au: 0.04 wt%), 3- and 14-times better than conventional Au@TiO2 yolk-shell nanostructure and pure TiO2 hollow nanosphere, respectively. Our unique design also notably achieves high selectivity (similar to 100%) towards CO production (0.75 mmol h(-1) g(-1)) under visible light irradiation. This unique yolk-in-shell nanoarchitecture promises enormous opportunities for the design of next-generation hybrid nanocatalysts with enhanced catalytic performances.
查看更多>>摘要：The effect of H2O on acetaldehyde oxidation was studied and alpha-, gamma-, delta-MnO2 can be affected by the H2O vapor, while beta-MnO2 is hardly affected by the H2O vapor during acetaldehyde oxidation. The H2O vapor can facilitate the catalytic oxidation of acetaldehyde at moderate temperatures (ca. 70 similar to 100 degrees C), with a negative effect observed at high temperatures (>100 degrees C). The stretching mode of the Mn-O-Mn chains in alpha-, gamma-, delta-MnO2 allows the associatively adsorbed water to absorb on the surface prior to acetaldehyde. Afterwards, acetaldehyde can form hydrogen bonds with the associatively adsorbed water molecules, thus, producing the intermediate carboxylic acid species, which are easily degraded to CO2. The negative effect of H2O on the acetaldehyde oxidation at high temperatures is attributed to the difficulty in adsorbing acetaldehyde on MnO2 via hydrogen bonding with the adsorbed H2O. These findings reveal the role of water in the catalytic oxidation of acetaldehyde.
Csepei, Lenard-IstvanRoth, Arnede Leon, Carlos PonceSieber, Volker...
13页
查看更多>>摘要：The electrochemical production of hydrogen peroxide (H2O2) from water is an appealing alternative to substitute the classic anthraquinone process. Herein, we show a process development to maximize the efficiency of the anodic production of H2O2. Carbon materials were used as anodes to optimize process parameters such as current density, electrolyte concentration, and the pH. We found that the electrolyte concentration, pH, and the presence of a chemical stabilizer have a substantial effect on the selectivity of water oxidation to H2O2. The addition of Na2SiO3 as a stabilizer increased the H2O2 production significantly at high pH regimes. A direct relationship between CO32- ion activity and enhanced production of H2O2 was also observed. We report H2O2 concentrations in the anolyte up to 33 mmol L-1 at a current density of 100 mA cm-2 using commercial and low-cost carbon fiber paper.
查看更多>>摘要：The development of robust and efficient hydrogen-evolving system remains a substantial but promising challenge to convert solar energy into clean fuel. Herein, we report the construction of water-compatible, robust, and ultraefficient hydrogen-evolving system by coupling water-soluble CdSe light-absorbers with Ni-substituted polyoxometalate (Ni-POM) catalysts and AA electron donor. Such facile catalytic system exhibits superior and robust hydrogen production activity to date even among known semiconductor/POM hybrids-based hydrogen production systems. Multiple stability experiments confirm the molecular stability of Ni-POM catalysts under turnover conditions. Various experimental and spectroscopic analyses reveal that the synergistic cooperation between high photostability of CdSe light-absorber, outstanding reversible multi-electron-transferring property of Ni-POM catalyst, and the fast hole-removing ability of AA electron donor account for the exceptional performance of present catalytic system. Our present work provides new research insights into the continued development of effective hydrogen-evolving systems through coupling other QDs-based light-absorbers and earth-abundant transition-metal-substituted POM catalysts.
查看更多>>摘要：NiSe2/Ni3Se4 dual-phase electrocatalysts are synthesized by calcining the Ni(OH)(2) nanosheets on Ni foam and Se powder under an N-2 atmosphere. The Ni's charge-state, phase compositions, and electrocatalytic performances are dependent on the initial mass ratios of Ni to Se. The experimental results demonstrate that the electrocatalyst with a higher Ni charge-state and more Ni3Se4 phase facilitates oxygen evolution reaction (OER), whereas the one with a lower Ni charge-state and more NiSe2 phase boosts hydrogen evolution reaction (HER). Density functional theory calculations reveal that the interfacial electrons transfer from Ni3Se4 to NiSe2, which improves conductivity and optimizes adsorption/desorption energies. NiSe2/Ni3Se4/NF-4 containing more NiSe2 phase displays the best HER activity while NiSe2/Ni3Se4/NF-1 containing more Ni3Se4 phase shows the best HER activity. The electrolyzer, employing NiSe2/Ni3Se4/NF-4 and NiSe2/Ni3Se4/NF-1 as the cathode and anode, respectively, performs the full potential and demonstrates a low voltage of 1.56 V achieving 10 mA cm(-2) with good durability.
查看更多>>摘要：Tuning surface properties of electrocatalysts for sustainable electrocatalytic nitrogen reduction reaction (NRR) with high selectivity and activity is highly demanded but still lacks fundamental understanding and modulation methods. Herein, we report the transformation of hydrogen evolution reaction (HER)-favorable cobalt phosphide (CoP) to NRR-favorable electrocatalyst via modulation of surface properties. The oxidized CoP particles encapsulated in carbon nanotubes (O-CoP/CNT) exhibits a high NH3 yield of 39.58 mu g h(-1) mg(-1 cat) as well as high Faradaic efficiency (FE) of 19.4% at -0.5 V vs. reversible hydrogen electrode (RHE), which is confirmed by N-15(2) isotope-labeling tests. In-situ Raman spectra identify that N-2 molecules are preferentially captured by Co ions, while the surface-adsorbed H+ are gradually eliminated. The hydrophobic surface of CNT can limit the contact of protons with the catalyst surface to inhibit HER, and the formation of hydrogen bond facilitates a more efficient NRR process. The surface modulation effects are confirmed by density functional theory calculations.
Mandal, SubrataNanavati, Sachin P.Willock, David J.Ananthakrishnan, Rajakumar...
20页
查看更多>>摘要：We developed a one-pot synthetic route to design Ag nanoparticles (NPs) coupled mixed ligand Ag(I) coordination polymer (CP), Ag@Ag(I)-CP (40% NH2) for photocatalysis. Initial combined (experimental and DFT) study on mixed ligand CPs demonstrates that a rational substitution of ligand L1 : 1,4-benzenedicarboxylate by L2: 2 amino 1,4-benzenedicarboxylate enhances porosity and reduction of energy gap (2.9 eV) due to highest occupied crystal orbital (HOCO; + 2.4 V vs. NHE) suitable for BA oxidation selectively to benzaldehyde (BD) ((E-BA/BD(0) = + 1.9 V). When Ag NP (similar to 6-7 nm) is in-situ encapsulated on CP, formed a coupled structure Ag@Ag(I)-CP (40% NH2), which offered advantages on BA oxidation (k (O-2) = 7.4 x 10(-4) min(-1); yield: 19.1% BD, and k (persulfate) = 38.7 x 10(-4) min(-1); yield: 54.1% BD) along with significant stability, reusability and competitiveness than other Ag or precious metal NPs. The new material offers numerous possibilities for applications in oxidative organic transformations reactions. The simple synthetic strategy demonstrated in this work for the coupling of Ag(I) based coordination polymers with metal nanoparticles at the molecular scale for semiconductor like applications under visible light will accelerate extensive research in near future.
Kovalskii, Andrey M.Volkov, Ilia N.Evdokimenko, Nikolay D.Tkachenko, Olga P....
16页
查看更多>>摘要：Environmental protection requires solving the problem of utilization and reduction of CO and CO2 emissions. Herein, Au/h-BN(O) and Pt/h-BN(O) nanohybrids are thoroughly analyzed in CO oxidation and CO2 hydrogenation reactions. The nanohybrids differ in catalytic particle size and particle distribution. The particles are smaller (1-6 nm) and display a narrower size distribution in the case of Pt-based nanomaterials. The Pt/h-BN(O) nanohybrids exhibit high catalytic activity in CO conversion and carbon dioxide hydrogenation reactions. For both systems, the oxidative state of BN support affects the catalytic activity. The possible catalytic reaction mechanisms are proposed based on DFT calculations. A charge density distribution at the Pt/h-BN interface increases oxygen absorption, thereby accelerating oxygen-associated chemical reactions.
查看更多>>摘要：Cobalt phosphide (CoPx) has been developed as a cost-effective cocatalyst for photocatalytic H-2 evolution with the advantages of excellent conductivity, strong reduction ability, good thermal and chemical stability. In this work, a facile preparation strategy was proposed to fabricate ultrafine CoPx nanoparticles on the surface of CdS. The effective H-2 production over ultrafine CoPx nanoparticles has been realized. In addition, we found Ca2+ as an alkaline earth metal ion can promote the interaction between CdS and CoPx. Both experimental results and density function theory indicate that the Ca2+ dopant can act as surface trapping sites on CdS and lead to efficient separation of photogenerated electron-hole pairs. The integration of CoPx and Ca2+ dopant can synergistically enhance both photogenerated electron-hole separation as well as interfacial charge transfer, which enables a remarkable improvement on the H-2 generation performance of CdS. The photocatalytic H-2 generation rate of Ca modified CoPx@CdS can reach up to 2441.5 mu mol h(-1) under optimal conditions with the apparent quantum efficiency as high as 35.4% at 420 nm. This finding motivates the development of simplified fabrication procedures for constructing and modifying cobalt active sites with efficient photocatalytic H-2 generation performance.
NSTL
Elsevier