查看更多>>摘要：Water vapor is inevitable in automobile exhaust and its influence on soot oxidation is of great interests to many researchers. In this paper, we utilized heavy-oxygen water ((H2O)-O-18) to investigate the water participation extent and its relationship with soot oxidation activity. By comparing the quantity of labeled species in products, we noticed water participated in both bare and catalytic soot oxidation. The tighter contact between soot and catalyst, the more involvement of water. But the extent was not affected by the redox property of Mn2O3 catalysts. The promotional effect of water on activity was observed in all investigated conditions, which was probably because water could be dissociated to more active oxygen species and accelerate the regeneration of oxygen vacancies. But hydrogen atoms left by water still need to be eliminated by dioxygen. Hence in general water worked as an accelerator rather than oxidant.
查看更多>>摘要：Development of high-efficiency electrocatalysts for pH-universal overall water splitting is a critical step towards a sustainable hydrogen economy. Herein, graphene nanocomposites with Ru-RuO2 Mott-Schottky heterojunctions (Ru-RuO2@NPC) are prepared pyrolytically and exhibit a remarkable electrocatalytic activity at pH = 0-14 towards both oxygen/hydrogen evolution reactions and overall water splitting, as compared to commercial RuO2 and Pt/C. Ru-RuO2@NPC can also be used as an effective air cathode catalyst for flexible, rechargeable zinc-air batteries. Density functional theory calculations show that the formation of Ru-RuO2 heterojunctions moderately enhances the surface charge density of metallic Ru and brings the d states closer to Fermi level, as compared to that of RuO2 alone, leading to improved intrinsic electrocatalytic activity towards these important reactions. These results demonstrate the significance of Mott-Schottky heterojunctions in the development of high-efficiency electrocatalysts for various new energy technologies.
查看更多>>摘要：N2-assisted thermal polycondensation of a novel supramolecular self-assembly based on melamine, cyanuric acid, and thiourea produced S-doped carbon nitride. Molecular dynamics simulation estimated nonbonding energies between the melamine-cyanuric acid adduct and thiourea. The C-S functional group was efficiently converted to C-O by facile calcination in a static air atmosphere, which gave a highly condensed O-doped carbon nitride nanosheet (O-CN). Density functional theory (DFT) calculations and experimental results confirmed that the oxygen-doped site is more stable and provides midgap states near the conduction band position of CN compared with sulfur doping. O-CN exhibited excellent visible light harvesting and photocatalytic activities toward removal of tetracycline and rhodamine B in an initial 15 min while producing a highly stable amount of H2O2 under an open atmosphere without a sacrificial agent. These outstanding performances result from synergistic approaches that lead to the modified polycondensation process, unprecedented reduction ability, and enhanced optical properties.
查看更多>>摘要：The development of electrocatalysts for nitrogen reduction reaction (NRR) at ambient conditions, with both high NH3 yield and Faradaic efficiency, is currently a great challenge. To this aim, a unique metal-organic framework (MOF) crystalline matrix with disulfide trimeric unit as the building block was in situ synthesized by integration of dynamic covalent chemistry and coordination chemistry. This MOF with high porosity and excellent stability could be used as a host material to encapsulate well-dispersed Au nanoparticles (NPs) with ultrafine size of 1.9 +/- 0.4 nm. After surface modification of Au@MOF by using organosilicone, the hydrophobic-treated Au@MOF (HT Au@MOF) composite shows remarkable electrocatalytic performances for NRR, with the highest NH3 yield of 49.5 mu g h-1 mgcat.-1 and the state-of-the-art Faradaic efficiency of 60.9% in water medium at ambient conditions. The favorable role of MOFs with functional sulfur groups on modulating the active Au sites and the great effect of hydrophobic coatings on suppressing the competitive hydrogen evolution reaction (HER) have been further demonstrated. This work provides a universal strategy to design composite electrocatalysts for high-efficient and long-term NH3 production.
De Sousa, Rafael A.Rasteiro, Leticia F.Vieira, Luiz H.Ocampo-Restrepo, Vivianne K....
13页
查看更多>>摘要：Supported Ni-Ga alloys have emerged as potential catalyst to mitigate CO2 emissions by its conversion into methanol at mild conditions, however, its performance depends on the optimization of the alloy-support effects, which is unclear up to now. Herein, we investigate the influence of alloy-support synergy in the catalytic performance of Ni5Ga3 supported on SiO2, CeO2, and ZrO2, by combining in-depth structural, chemical and spectroscopic characterization and density functional theory (DFT) calculations. In situ DRIFTS confirmed further hydrogenation of key reaction intermediates in Ni5Ga3/ZrO2 surface, while weak CO2 adsorption in Ni5Ga3/SiO2 avoided intermediate stabilization on the surface and, strong interaction with Ni5Ga3/CeO2 poisoned interface active sites. Additionally, the relative energies of reactants and key intermediates in the three distinct regions of the catalyst (support surface, alloy surface, and alloy-support interface), calculated through DFT, allowed us to propose a reaction mechanism for the most promising catalyst, Ni5Ga3/ZrO2.
Garcia-Segura, SergiCerron-Calle, Gabriel AntonioFajardo, Ana S.Sanchez-Sanchez, Carlos M....
10页
查看更多>>摘要：Identifying electrocatalytic materials that generate fossil-free ammonia through N-recycling from polluted water sources is required. Bimetallic Cu-Pt foam electrodes were synthesized to enhance electrochemical reduction of nitrate (ERN) by the introduction of bimetallic catalytic sites. Electrodes were benchmarked against Cu foam using engineering figures of merit. Cu-Pt (180 s) electrode achieved 94% conversion of NO3--N in 120 min yielding 194.4 mg NH3- N L-1 g(cat)(-1), with a selectivity towards ammonia (S-NH3) of 84% and an electrical energy per order decrease by similar to 70% respect pristine Cu foam. Bimetallic electrodes with low Pt loadings (<0.50 wt%) demonstrated that synergistic effects of Cu-Pt nanointerfaces enabled hybridized mechanisms of catalytic electrochemical and hydrogenation reduction processes. These encouraging outcomes emphasize the potential of Cu-Pt foam electrodes to treat contaminated water sources with nitrate, while allowing a sustainable decentralized ammonia recovery. Enriched water for crops irrigation can therefore be a prospect use for this added value product.
查看更多>>摘要：The utilization of solar energy for hydrogen peroxide (H2O2) production using graphitic carbon nitride (g-C3N4) under visible light irradiation has attracted increasing interests due to its high efficiency and cost-effectiveness. However, this process is still limited by slow charge carrier migration. In this work, continuous regulation of band structure inside g-C3N4 is obtained by defect engineering through gradient calcination. The H2O2 production rate (4980 mu mol g-1 h-1) of nitrogen-defective g-C3N4 is 18 times higher than that of pristine g-C3N4. The pi*C--N-C signals in X-ray absorption near-edge structure spectrum decline, indicating an increased N-defects. The N-defects with the electronic vacancies in the heptazine intensifies its light-harvesting on g-C3N4 and also improve the selectivity of 2-electron O2 reduction. A quantitative structure-activity relationship between Ndefects and band structure is unveiled. This work offers an accessible strategy to design photocatalysts with desirable defect structures for energy conservation.
查看更多>>摘要：Developing the electrocatalysts which can be directly performed in sewage and seawater without further treatment kills two birds with one stone since it can turn waste into raw materials and produce H2. Herein, the heterointerface between Fe(Cr)OOH and Fe3O4 is constructed through a scalable method. Systematic experiments and theoretical calculations confirmed that the Fe(Cr)OOH coupling with Fe3O4 can significantly decrease the oxygen evolution reaction (OER) overpotential (eta 500 = 241 mV in 1 M KOH) and promote the mass and electron transfer. Impressively, this electrode could work efficiently and maintain 100 mA cm-2 for 100 h in both alkaline seawater and domestic sewage. The electrolyzer using such electrode as anode could deliver a current density of 500 mA cm-2 in 5 M KOH at a small cell voltage of 1.62 V. This work provides a facile route to prepare efficient and low-cost OER catalysts, which has important implications for energy conversion.
查看更多>>摘要：Innovating new Co-based materials to outperform widely-used Co3O4-based ones for eliminating recalcitrant pollutants via peroxymonosulfate (PMS) activation is dauntingly challenging. Herein we highlight for the first time that Co4N is a new-generation PMS activator, and illuminate comprehensive understanding of intrinsic activity correlated with coordination environment of Co site. The nanocomposite comprising Co4N nanoparticles immobilized on rGO, derived from a metal-organic complex, presents remarkable catalysis for 4-chlomphenol degradation via PMS activation, particularly, up to 42 times of promotion is harvested relative to Co(3)O(4-)based catalyst with similar morphology (0.682 vs 0.016 min(-1)). Theoretical calculations unravel that with respect to the common-used Co3O4 and Co, Co4N featuring N incorporated into interstices of Co framework has more suitable electronic structure to render optimal binding strength for PMS activation. This work points to the potential of Co-based nitrides for PMS activation, and enlightens that subtle engineering over coordination environment and architecture promises boosted catalysis.
NSTL
Elsevier