查看更多>>摘要：Reasonable regulation of the interaction between metal center and the ligand to achieve a high-density atomic loading without agglomeration has been the formidable challenge to the development of single-atom catalysts (SACs). Herein, an advanced photocatalyst based on N-vacancy (Nv) tubular porous g-C3N4 (TCN) decorated with atomically dispersed Mo (Mo/Nv-TCN) is synthesized. The large specific surface area of the tubular morphology contributes to suppress the agglomeration of Mo atoms, while the N defect induces the formation of specific stable Mo-2 C/2 N configuration between the light absorbers and the Mo sites. As the active center of the photocatalytic reaction, single Mo atom causes the directional transfer of local charges on the surface of the support, while the Mo-2 C/2 N bond acts as a bridge for photoexcited charge transfer. As a result, the precisely designed Mo SACs system shows remarkable photoelectric properties and renders excellent photocatalytic performance for tetracycline (TC) degradation under visible light irradiation.
查看更多>>摘要：Insufficient charge-carriers separation and deteriorated recycling are still bottlenecks limiting practical photo-catalytic water purification. Herein, we developed a durable hollow core-shell TiO2@LaFeO3(TLFO) nanosphere via facile carbon-sphere-templated method and sol-gel process, and applied it as heterojunction photocatalyst coupled with peroxymonosulfate (PMS) for efficient atrazine (ATZ) removal via enhanced electron-transfer. The built-in electric field originated from the three-dimensional heterojunction between TiO2 and LaFeO3, acting as charge transfer driving force, enhanced the charge separation rate. Meanwhile, PMS could function as electron acceptor to boost photogenerated charge separation and maximize reactive oxidant species (e.g., (OH)-O-center dot, SO4 center dot-, O-2(center dot-) and O-1(2)) production. Therefore, the fabricated TLFO heterojunction exhibited outstanding reusability, and superior ATZ removal efficiency without detectable metal ion leaching. This work successfully demonstrates the synergistic effect and superior hollow structure of TLFO heterojunction with promoted light utilization and PMS activation, which offers potential application for efficient abating environmental pollution using solar energy.
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.
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.
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：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.
查看更多>>摘要：Removal of formaldehyde (HCHO) has recently been attracted much attention, and completely catalytic oxidation at room temperature has been identified as one of the efficient routes for solving this problem. In this research, we show a successful preparation of Ag-loaded octahedral molecular sieve from solvent-free route (Ag/OMS-2-S), which was characterized by XRD, SEM, HRTEM, BET, XPS, ICP-OES, H-2-TPR, and HCHO-TPD techniques to investigate the factors influencing the catalytic activity. Very interestingly, HCHO is completely converted into CO2 at room temperature over the Ag/OMS-2-S catalyst. To the best of our knowledge, this is the first time for complete oxidation of HCHO at room temperature over all the Ag-based catalysts. Relating to the characterizations, it is suggested that the active oxygen species play a key factor that contributes to the excellent performance of the Ag/OMS-2-S. In addition, the Ag/OMS-2-S catalyst is also very stable and selective. Combination of extraordinary activity and excellent stability of the Ag/OMS-2-S catalysts might offer an alternative way to develop new efficient catalysts for the removal of air pollutants.
查看更多>>摘要：The current study investigates Ce-modified SrFeO3-delta oxygen carriers for oxidative dehydrogenation (ODH) of ethane coupled with CO2 splitting in a chemical looping manner. During 39 cycles of redox testing over the sample of 0.2Ce/SrFeO3, up to 29% ethane conversion and 82% ethylene selectivity are achieved, and the CO generation in the subsequent CO2 splitting step is 0.25 mmol/g. XPS characterization results indicate decreased Fe2+/(Fe3++Fe4+) ratio as well as increased active oxygen species proportion on the near-surface of Ce-modified samples, which are responsible for the improved activity of the 0.2Ce/SrFeO3 in ethane ODH reaction. DFT calculations further reveal that the increased ODH activity of 0.2Ce/SrFeO3 is due to the lower surface oxygen vacancy formation energy upon Ce promotion. Moreover, the higher resistance of lattice oxygen diffusion from the bulk to the surface is the main reason for the superior ethylene selectivity attained by the CO2-regenerated sample than that by O-2 regeneration.
NSTL
Elsevier