查看更多>>摘要：Defect engineering is an effective way to unveil relationship within structures and catalytic activities of transition metal oxides. Herein, a novel strategy has been developed for in situ generation and controlling oxygen vacancy (Ov) levels in a host lattice by varying oxygen pressure during calcination of zeolitic imidazolate framework-67 (ZIF-67) membranes. The as-prepared NFZ-5 membrane with the largest Ov content (delta, 0.912) gave the highest 1O2 production (98.3%) and PMS activated BPA degradation kinetics (k = 0.11 min-1). Advanced characterization and density functional theory (DFT) calculations have revealed the pivotal role of Ov in modifying surface chemistry of the catalytic membrane via enhancing the number of Lewis acid sites. These Lewis acid sites have facilitated the chemisorption of peroxymonosulfate (PMS) onto membrane, and the resulting reactive intermediate complexes have altered the electron transfer direction between PMS and the catalyst.
查看更多>>摘要：The construction of multifunctional supramolecular assembly is a central research interest in solar-driven water splitting to hydrogen. We here report the successful preparation of a dual-functional supramolecular assembly via facile electrostatic integration of a positively-charged Ir-based chromophore and a negatively-charged nickel substituted polyoxometalate catalyst. The resulting dual-functional supramolecule can form ordered vesicle-like assemblies and work efficiently as both light-absorber and catalyst for hydrogen production under visible light irradiation. Under minimally optimized conditions, a catalytic hydrogen production turnover number of over 4000 was achieved after 96-hour irradiation, which is 17 times to that of discrete components under otherwise identical conditions. Destruction of such ordered vesicle-like assemblies will lead to a remarkable decrease of photocatalytic hydrogen production activity. Mechanistic studies further revealed the presence of both oxidative and reductive quenching processes during photocatalysis and also confirmed that the formation of ordered supramolecule is beneficial for effective electron transfer between chromophore and catalyst.
查看更多>>摘要：The generation of free radicals was enhanced by triboelectric pulsed direct-current during the organic pollutant degradation. The self-powered electrochemical system was constructed for enhancing 4-CP removal powered by a water-driven triboelectric nanogenerator (WD-TENG). The output of current, voltage, and power of WD-TENG were studied. The removal of 4-CP and its degradation mechanism were also discussed. The results shows that the formation of hydroxyl radicals (center dot OH) was improved by improving PMA(Mo5+) conversion efficiency by the WD-TENG in the phosphomolybdic acid/H2O2 (PMA/H2O2) system, resulting the mineralizing the 4-CP via dichlorination and oxidation. The removal of 4-CP improved by 10% in 120 min in the WD-TENG powered electro-PMA/H2O2 system. This study provides a promising methodology for improving the performance of self-powered electrochemical processes for the treatment of environmental pollution.
查看更多>>摘要：The complete conversion of lignocellulosic biomass to selective and highly valuable chemicals is challenging because of its inertness and complexity. Herein, we report a direct chemocatalytic route for the complete one-pot conversion of raw woody biomass to cyclic ketones and aromatic monomers over a multifunctional bi-metallic Cu-Ru catalyst on HZSM-5 (Cu-Ru/Z). The Si/Al ratio of HZSM-5 plays an effective role in the product distribution. High-yield ketones (60.9% based on carbon in holocellulose) and aromatics (28.4% based on carbon in lignin) were produced in an aqueous medium. Three strategies, metal domain encapsulation inside the zeolitic framework, SiO2 layer coating, and carbon layer coating, were employed to overcome the weak hydrothermal stability associated with HZSM-5. The carbon-coated Cu-Ru/Z catalyst exhibited high stability up to three reaction cycles. Optimization of the reaction conditions, reaction mechanisms for the selective ketone synthesis, and catalyst deactivation mechanisms are discussed.
查看更多>>摘要：Synthesizing the catalysts with high activity and stability has always been the research hotspot in the field of heterogeneous catalysis, and the confinement provides a promising route to achieve the goal. Herein we report the porous TiO2 nanotube confined Pt catalysts synthesized by the template-assisted atomic layer deposition (ALD) strategy for hydrolytic dehydrogenation of NH3BH3, in which the ultrafine Pt nanoparticles are decorated on the inner surfaces of the nanotubes with increased Pt-TiO2 interfacial sites compared with the supported Pt/TiO2 counterparts. Combined with the porous structures of the nanotubes with suitable thickness and large open ends, these factors synergistically contribute to the excellent catalytic performances of the confined Pt@TiO2 catalysts. The present strategy can be extended to prepare the corresponding PtNi@TiO2 bicomponent catalysts exhibiting the further boosted activity with a TOF value of 1055.2 mol(H2) mol(Pt)(-1) min(-1). This work offers a reliable and general approach for synthesizing the confined catalysts with high efficiency.
查看更多>>摘要：Chemical looping ammonia synthesis (CLAS) is an innovative and effective method for sustainable ammonia generation, in which efficient N release/fixation of nitrogen carriers (NC) is required for successive ammonia production. Herein, we report a two-step CLAS mediated by a Mo2N-Mo couple and experimentally validate its N fixation and N release steps under mild conditions. In the N-release step, the NH3 production rate at 450 degrees C (> 4576 mu mol g(-1) h(-1)) was three times higher than that obtained via the thermo-catalytic ammonia synthesis route catalyzed by Mo2N. In the N-fixation step, the introduction of H-2 enhanced the reaction kinetics between Mo and N-2, accelerating NC regeneration. In addition, only a slight deactivation of NC was observed during the 8-cycle stability test. This study confirmed the preliminary feasibility of using Mo2N as an NC during the CLAS process.
查看更多>>摘要：Electrochemical CO2 reduction reaction (eCO(2)RR) to syngas (CO + H-2) is considered as a great potential and efficient way to abate carbon emissions and mitigate the depletion of fossil resources. Herein, a series of Pd-loaded SnO2 nanosheets catalysts (Pd-SnO2 NSs) are developed by photodeposition of Pd on the surface of SnO2 nanosheets. Due to the formation of the active Pd-SnO2 interface, the as-prepared Pd-SnO2 catalysts exhibit a suppressed eCO(2)RR to HCOOH pathway, thus realizing the faradaic efficiency of syngas close to 100%. The obtained optimal 4.3Pd-SnO2 catalyst exhibits high CO selectivity (78% FECO) and wide H-2/CO ratio ranged from 4.2 to 0.28. Notably, the H-2/CO ratio can be controlled easily by adjusting the applied potential. Moreover, the H-2/CO ratio can maintain for more than 30 h. This work unfolds a promising candidate for earth-abundant Sn-based electrocatalysts for eCO(2)RR to syngas.
查看更多>>摘要：Herein, a photocatalysis-self-Fenton system was constructed to achieve unprecedentedly efficient degradation and mineralization performance towards organic pollutants. This system is based on oxygen-doped porous gC3N4 nanosheets (OPCN) with high H2O2 yield and the added Fe3+. The corresponding degradation rate for 2,4dichlorophenol was 11.5 and 9.9 times higher than that of bulk-g-C3N4-based photocatalysis and Fenton system, respectively, while the mineralization rate was 11.4 and 4.2 times higher, respectively. The excellent oxidation capacity was due to three reasons: (1) the porous nanosheet morphology and oxygen doping of HCNS accelerated the carriers transfer and provided more reactive sites for H2O2 synthesis; (2) Fe3+ was reduced into Fe2+ by photogenerated electrons, further inhibiting the charge recombination and promoting the cyclic conversion of Fe3+/Fe2+; (3) the high-efficiency utilization of in-situ generated H2O2 was realized via heterogeneous Fenton reaction, producing abundant center dot OH. This work provides a new strategy to develop g-C3N4-based photocatalysisself-Fenton system for environmental remediation.
NSTL
Elsevier