查看更多>>摘要：Developing efficient and stable OER catalysts is conducive to improving hydrogen production efficiency and achieving "carbon neutrality " goal. Herein, a CoNi nano-alloys modified yolk-shell carbon cage (CoNi/NC-YS) catalyst was synthesized through a green synthesis method, which shows an outstanding OER activity with a low overpotential of 292 mV at 10 mA.cm(-2), and a robust OER catalytic stability. The experimental and density functional theory (DFT) results demonstrate that the hydrophilic yolk-shell CoNi/NC-YS catalyst with large specific area contributes to exposing more active sites, and increases the reaction contact area between catalysts and electrolyte. Meanwhile, CoNi nano-alloys can regulate the electronic configuration of CoNi/NC-YS catalyst and optimize Gibbs free energies for water adsorption, accelerating OER process in alkaline media and showing an outstanding OER performance. This work can provide a low-cost and green strategy to construct nano-alloys modified yolk-shell OER catalysts for renewable energy systems.
查看更多>>摘要：As a typical carcinogenic phenolic environmental pollutant, hydroquinone (HQ), its effective catalytic conversion is particularly urgent for environmental protection. However, the development of low-cost, high-efficiency catalysts still faces many challenges. Furthermore, the mechanism for efficient catalysis has not been established. In this paper, a trace amount of Pd-supported 3D urchin-like Pd/W18O49 composite in an aqueous solution was reported as a high-quality catalyst for the H2O2 catalytic oxidation of hydroquinone (HQ) to benzoquinone (BQ) with a turnover frequency (TOF) of 1750 h(-1), exceeding commercial catalyst. Through experiments combined with density functional theory (DFT) calculations analysis, this excellent catalytic effect is mainly attributed to the existence of an electronic induction effect between W18O49 and Pd nanoparticles (NPs). Meanwhile, the abundant oxygen vacancies on the surface of W18O49 can stabilize the & BULL;OH radicals generated from the decomposition of H2O2, thus promoting the breakage of O-O bonds to generate more center dot OH radicals and achieve an effective oxidation reaction. In addition, the influencing factors such as catalyst and HQ concentration, solution pH, solvent, various inorganic and organic interferences were comprehensively investigated. The 3D urchin-like Pd/W18O49 catalyst also showed an excellent effect on the catalytic oxidation of HQ derivatives with high TOFs.
Azzoni, Maria ElenaFranchi, Federico SaschaUsberti, NicolaNasello, Nicole Daniela...
9页
查看更多>>摘要：A new dual layer monolithic AdSCR system (adsorption + selective catalytic reduction) constituted by Cu/CHA (top) and BaO/Al2O3 (bottom) was prepared and studied as a potential solution to improve the low-T performances of NH3-SCR catalysts. Two washcoat formulations were considered. The samples were characterized through optical microscopy and SEM-EDX; the ammonia storage capacity and the catalytic activity in the standard NH3-SCR reaction were also studied. When using water as solvent during the deposition, migration of Ba into the Cu-zeolite layer was observed, resulting in a decay of both ammonia storage capacity and NH3-SCR activity. On the other hand, when water was replaced by n-butanol, the two layers were well segregated, and no loss of SCR performances was noted. The butanol-based formulation exhibited promising performances in the NOx abatement during cold-start transients, with a NO removal efficiency of 31%, prior to ammonia injection, and of 52% after ammonia injection.
查看更多>>摘要：By doping 1%Ru/m-ZrO2 with sodium, selectivity tuning between CO and CH4 during CO2 hydrogenation was achieved by controlling the relative rates of reverse water-gas shift and CO methanation. By increasing basicity through Na loading: (1) the formate C-H bond is weakened in DRIFTS of adsorbed CO, accelerating C-H bond formation of formate and promoting CO formation at the Ru/m-ZrO2 interface; and (2) the coverage of Na increases on ensembles of Ru atoms responsible for methanation. Increasing Na content shifts selectivity from CH4 (useful for synthetic natural gas) to CO, which can be used for Fischer-Tropsch synthesis or methanol-to-gasoline. Electronic modification of formate is likely due to enhanced basicity (strengthening bonding between catalyst and the-CO2 function of formate and weakening C-H). No electron transfer from Na to Ru was detected in XANES. DRIFTS as a function of time and XPS results showed that Na exacerbates site blocking and deactivation.
查看更多>>摘要：Developing sulfur resistant and stable hydrogenation catalysts with a high activity is of great economic and environmental interest for the production of value-added fine chemicals, as it allows the use of crude industrial level raw materials as reactant, prevents environmental unfriendly stoichiometric reduction and cuts down energy-intensive separation/purification procedures. Here we show the metallic Ni nanoparticle well-enclosed in multilayer N doped graphene shells for the catalytic hydrogenation of nitrobenzene derivatives. The nickel core promoted multilayer N doped graphene shell not only maintains the hydrogenation ability but also create a differentiate surface electronic state preventing the poisoning of vulnerable metal by S impurities. The catalytic performance has met the product requirement of hydrogenation of industrial raw materials including 4.00 wt% inorganic/organic sulfur poisoning substances, excessive acid residue and concentrated salts.
查看更多>>摘要：Catalytic methanol production from CO2 hydrogenation at a lower temperature is limited, predominantly constricted by sluggish reaction kinetics. In this work, a ceria-modified Cu/ZnO/Al2O3 catalyst (CuZnCe-Al) is fabricated which delivers efficient low-temperature methanol production (yield= 822 g/kg(Cu)/h and selectivity = 94% at 225 C and 20 bar) under light illumination. The influence of ceria loading on the morphology/microstructure, interfacial features, and surface chemistry of a Cu/ZnO-based catalyst is systematically assessed. Incorporating ceria (<= 10 at%) into ZnO initially forms ZnO/CeOx interface which promotes both CO2 chemisorption and the formate-pathway which favours methanol production over CO. Increasing the ceria loading beyond 10 at% invoked a Cu/CeOx-dominated structure, leading to over-stabilisation of the surface reaction species and a decreased preference for methanol. The photo-enhancement factor observed for each CuZnxCey catalysts is largely independent of the ceria loading, implying that ceria inclusion imposed little influence on the Cu-ZnO interfacial characteristics.
查看更多>>摘要：Developments of Fe-TAML/H2O2 systems were conducted for the removal of refractory organic micropollutants in water. Herein, we investigated degradation of 68 structurally diverse sulfur-containing micropollutants (ng/L-mu g/L) in water by Fe-TAML/H2O2, and developed predictive models of the reactivity of Fe-TAML/H2O2 using micropollutant, Fe-TAML and H2O2 data. The micropollutants were usually degraded rapidly in water within 20 min, and the k(obs) values (0.0054 to > 0.47 min(-1)) drastically varied with compounds and/or solution pH. Static complexation and electron transfer between Fe-TAML and compounds were proposed for the high reactivity and selectivity of Fe-TAML/H2O2 toward micropollutant over naturally occurring dissolved organic matter (DOM). The mechanism-based reaction models of Fe-TAML/H2O2 were well extrapolated to large diversities of organic compounds and various types of water. This study indicates that Fe-TAML/H2O2 systems may provide a technical basis for the removal of micropollutants in water, despite the presence of high levels of natural water components.
查看更多>>摘要：Engineering the interfacial active sites in metal modified semiconductor photocatalysts is highly promising but still challenging for developing heterogeneous photocatalysts with high activity and selectivity. Herein, the Ru/ g-C3N4-x photocatalyst consisting of small Ru nanoparticles (NPs) anchored on defective g-C3N4-x nanoflakes with nitrogen-vacancies (VNs) is prepared by a photoinduced method, where the photoexcited electrons of gC(3)N(4) enable the deposition of Ru NPs and the hole-generated oxidative radicals induce the formation of VN defects on g-C3N4. The Ru/g-C3N4-x photocatalyst exhibits excellent performance toward the photocatalytic redox coupling reaction of hydrogen evolution and selective oxidation of benzyl alcohol, showing the generation rates of hydrogen and benzaldehyde up to 6.42 and 5.07 mmol.g(cat)(-1).h(-1), respectively. The underlying photo catalytic mechanism is elucidated by a series of control experiments, in situ characterizations and theoretical calculations. Both experimental and theoretical studies elucidate that the synergy of interfacial Ru sites and VN defects on g-C3N4-x plays a critical role in boosting the photocatalytic redox coupling reaction. The Ru/g-C3N4-x heterointerface not only accelerates the separation of photogenerated charge carriers but also provides the optimum active sites for H-2 evolution and benzyl-alcohol oxidation.
查看更多>>摘要：Designing atomically dispersed non-precious metal catalysts for 2e(-) oxygen reduction reaction (ORR) is an appealing strategy to harness O-2-to-H2O2 chemistry. Nevertheless, prevailing M-N-C single-atom catalysts (SACs) might still not satisfy the directional regulation of ORR selectivity, hence fail to uphold scalable H2O2 electrosynthesis with a high yield. Herein, we report the precise synthesis of (O,N)-coordinated Fe SAC (FeN2O2) and relating investigation of its performance in H2O2 production over a wide pH range, in comparison with the FeN4 counterpart. Density functional theory simulations reveal that the coordination chemistry engineering has a profound influence on the strength of the oxygen intermediate adsorption. The electron delocalization of M-O configuration readily lowers the d-band center of the Fe metal, which is beneficial to weakening the intermediate adsorption capability and promoting the 2e(-) ORR process. The thus-derived FeN2O2 exhibits impressive selectivity in a wide pH range, particularly reaching 95% in alkaline conditions. Furthermore, our designed gas-diffusion electrode enables a favorable H2O2 yield (300 mmol L-1) at a current density of 60 mA cm(-2) for 50 h. This work is anticipated to inspire the rational design of definitive SAC architecture for practically feasible electrochemical production of H2O2 toward environmental remediation.
查看更多>>摘要：Here, we present a new preparation strategy for hollow SAPO-34 with hierarchical porous structures using rice husk as a sole silicon source and porous template (viz., bio-SAPO-34). The hollow feature and acidity amount of the bio-SAPO-34 were highly dependent on the amount of rice husk in the synthetic solutions. The bio-SAPO-34 exhibited very high olefin selectivity (94.5 %) in the methanol-to-olefins reaction. Bifunctional catalysts con-sisting of ZnZrOx and bio-SAPO-34 were fabricated for the direct conversion of CO2 to light olefins. The C-2(=)-C-4(=) selectivity of 83 % and C-2(=)-C-4(=) space-time yield of 6.14 mmol g(cat)(-1) h(-1) was achieved with only 1 % undesired CH4 at 13.8 % CO2 conversion. Particularly, the CO selectivity from the reverse water-gas shift reaction was sup-pressed to a low value (40 %). Furthermore, the in-situ DRIFTS result indicates that CH3O* is the key interme-diate forming on the ZnZrOx surface and transferring to the Bronsted acid site of bio-SAPO-34 for selective C-C coupling.
NSTL
Elsevier