查看更多>>摘要：Selective oxygenation of alkanes via C-H bond activation still remains a challenge because the oxygencontaining products are more active than the substrates. Here, we develop a new concept of eco-friendly zeolite-fixed photocatalyst to impart catalytic performance via loading CuCl2 upon visible-light irradiation. Complete selectivity in terms of the final oxidation product KA-oil was obtained with 24% conversion in the application of cyclohexane oxidation. After optimization, the desired ketones and alcohols were also obtained in good to excellent selectivities with broad substrate scope. Multiple experimental studies combined with theoretical calculations demonstrate that the formation of the unique CuCl2/TS-1 hollow structure with isolated CuCl2 species anchored onto the inner and outer surface of TS-1 shells: the function of the major tetrahedral Ti-O4 sites in heterojunctions to isolate energy levels near the conduction and valence bands. In photocatalysis, the presence of Cu-O-Ti-O3 heterojunctions facilitates separation and transfer of photogenerated electrons and holes
查看更多>>摘要：Dry reforming of methane provides a feasible solution to reduce the greenhouse gas via simultaneously converting CH4 and CO2 into useful syngas. However, conventional Ni-based catalysts suffer from deactivation due to serious carbon coking during dry reforming of methane process. Herein, we propose a concept by reducing crystallinity of formed carbon and accelerating carbon oxidization to enhance the coking resistance of Ni-based catalysts. This concept was conducted through a boron nitride coating strategy over reducible oxides supported Ni catalysts, in which the increased carbon diffusion barrier, induced by the boron nitride coating, would lead to more amorphous carbon. While the amorphous carbon was efficiently gasified by active oxygen species derived from reducible oxides. Our findings demonstrate that the coke issues can be solved by building a dynamic carbon removal route.
查看更多>>摘要：The design and development of highly efficient non-precious metal single-atomic ORR catalysts for proton exchange membrane fuel cells (PEMFCs) are highly desirable but challenging. Herein, we report a novel polydopamine (PDA)-metal complex-assisted pyrolysis strategy for producing zeolitic imidazolate framework-derived catalysts with a hierarchically porous carbon support and highly exposed dense-FeN4 sites (Z8@DA-FIP-950-C). The resultant Z8@DA-FIP-950-C catalyst shows remarkably enhanced performance for oxygen reduction reaction (ORR) with a half-wave potential (E1/2) of 0.828 V in 0.1 M HClO4 solution, which is close to commercial 20 wt% Pt/C catalyst. Impressively, the Z8@DA-FIP-950-C exhibits peak power densities of 982 and 454 mW cm-2 in H2/ O2 and H2/air PEMFCs, respectively, which are superior to most of non-precious metal catalysts reported to date. In addition, we construct the quantitative relationship between the active site activity and ORR performance, and prove the dominating role of the FeN4 site density to the observed excellent PEMFC performance. This work demonstrates a facile strategy to prepare the 3D hierarchically porous carbons with a maximized exposure of high-dense FeN4 sites (without acid treatment), providing a useful guidance for the design and development of novel highly-efficient single-atom catalysts for the renewable energy applications.
查看更多>>摘要：Electrochemical reduction of CO2 (CO2RR) to value-added chemicals is a feasible strategy to build a carbon neutral society and store energy. However, the sluggish kinetics of CO2RR accompanied by competing hydrogen evolution reaction (HER) makes the practical application of this process very challenging. Herein, we construct a Ni/Ni3ZnC0.7 heterostructured catalyst wrapped in porous N-doped carbon nanofibers via a facile electrospinning strategy for CO2RR. Remarkably, the as-prepared Ni/Ni3ZnC0.7 catalyst exhibits a high selectivity of 91.5% toward CO, a superior CO partial current density of 11 mA cm(-2) at -0.8 V versus the reversible hydrogen electrode (vs. RHE) and maintaining 93.4% of its initial selectivity after 45 h of continuous electrolysis. The calculation results of density functional theory (DFT) show that the heterostructure of Ni/Ni3ZnC0.7 catalyst is beneficial to the formation of *COOH and enhances the efficiency of electrocatalytic CO2 conversion.
查看更多>>摘要：The instinct scaling relations between the adsorption energies of key intermediates during OER lead to large overpotential for water/seawater splitting. Herein, we develop a new strategy to fabricate amorphous nickel-iron phosphides (NiFeP) with controllable morphologies as high-performance catalysts for overall seawater splitting. The ligand effect of P tunes the electronic states of the oxidized NiFe sites, thus breaks the scaling relations for OER and reduce the adsorption energy gap between HO* and HOO* from 3.08 eV to 2.62 eV. The NiFeP nanostructures exhibit extraordinarily low overpotentials of 129 mV for OER and 126 mV for HER at 100 mA cm-2 in simulated alkaline seawater, which outperform the best reported electrocatalysts. They could also be operated at 1.57 V with 100 mA cm-2 in a two-electrode electrolyzer and work for more than 500 h. Our work may provide a universal guidance for the design of highly active seawater splitting electrocatalysts.
查看更多>>摘要：Developing an in-situ soil remediation technology for simultaneous catalytic degradation of contaminants and nitrogen supplementation is of great importance but remains challenging. Herein, MgFe-LDH engineered biochar (MB) was successfully synthesized by using a simple co-precipitation method. The as-prepared materials were used as catalysts for the first time to activate urea-hydrogen peroxide (UHP) to degrade antibiotic sulfamethoxazole (SMX) and provide nitrogen. The enhanced degradation efficiency of SMX (91%) were mainly attributed to center dot OH and 1O2-mediated oxidation. Pot experiments showed MB/UHP significantly decreased the SMX concentration from 6.47 to 2.10 mg kg-1 and simultaneously increased NH4+-N and NO3--N concentration. The optimal quantitative-structure-activity-relationship model for 19 antibiotics suggested the dipole moment, energy of the highest occupied molecular orbital, and bond order were the intrinsic influencing factors. This study not only provides a green remediation technology but also offers a theoretical basis for estimating the removal rate of unexplored antibiotics.
查看更多>>摘要：A novel p-n heterojunction between Ag3PO4 and nitrogen-doped black TiO2 (b-N-TiO2) was successfully synthesized via the calcination and precipitation method. The incorporated nitrogen and produced oxygen vacancies in b-N-TiO2 narrowed the bandgap and shifted the band position of TiO2, which promoted p-n heterojunction formation and subsequently facilitated the separation of photogenerated electrons and holes in the composite bN-TiO2/Ag3PO4. The b-N-TiO2/Ag3PO4 exhibited enhanced photocatalytic activity for chlorophyll-a degradation in Microcystis aeruginosa cells, which was 2.73, 7.72, and 6.04 times higher than that of the pure Ag3PO4, b-NTiO2, and P25/Ag3PO4, respectively. Furthermore, the mechanism exploration indicated the transfer pathways of photo-produced electrons and holes to generate the dominant superoxide anion radicals (center dot O2-) in photocatalytic processes. The charge transfer increased the photocatalytic stability of the composite b-N-TiO2/Ag3PO4 compared with pure Ag3PO4 and P25/Ag3PO4. This research provides a new perspective into the roles of defects to form heterojunctions in photocatalytic composites.
查看更多>>摘要：Direct hydrogenolysis of glycerol to ethanol in liquid phase was studied for the first time in this work, and the results showed that Pd/CoOx gave high ethanol selectivity and good reusability. The reaction pathways were thoroughly investigated, and it was found that ethanol was mainly produced by consecutive hydrogenolysis of glycerol with 1,2-propanediol as intermediate. More importantly, PdCo alloy was identified as the main active site for ethanol production from glycerol by in situ XRD, TEM, H2-TPR, XPS and controlled experiments. Remarkably, Cu/SBA-15 was employed as co-catalyst to adjust the reaction routes and inhibit Pd/CoOx aggregation. By synergistic catalysis of Pd/CoOx and Cu/SBA-15, the yield of ethanol then reached to 84.5%, which is the highest value ever reported in glycerol hydrogenolysis reactions.
查看更多>>摘要：Photoreforming of lignocellulosic biomass is an emerging and sustainable strategy for coproduction of high-value chemicals and fuels. Challenges remain to selectively convert biomass macromolecular via sunlight-driven photocatalysis due to limited mass diffusion, insufficient charge separation and lack of mechanistic understanding. Herein, inspired by natural photosynthesis, we demonstrate a hierarchically threedimensionally ordered macroporous (3DOM) TiO2-Au-CdS Z-scheme heterojunction photocatalyst to improve mass diffusion, charge separation and light absorption efficiency. We show the photocatalytic cleavage pathway of cellulose beta-1,4-glycosidic linkage (the most abundant linkage within biomass) over 3DOM TiO2-Au-CdS heterojunction by using cellobiose as a model component. Similar to the oxidative enzymes in nature, the all-solid-state Z-scheme photocatalyst demonstrates oxygen insertion at Cl position followed by the elimination reaction, which oxidatively cleaves the beta-1,4-glycosidic bond and results in gluconic acid and glucose generation. In presence of oxygen, glucose is further oxidized into gluconic acid which is subsequently oxidized or decarboxylated into glucaric acid or arabinose. The present study may serve as a framework to rationally design photocatalyst to reveal mechanistic understanding of biomass photoreforming towards high-value fuels and chemical feedstocks.
查看更多>>摘要：Photo-oxidative NOx removal often encountered with sluggish charge carrier separation kinetics and poor selectivity. Herein, Pd/ferroelectric Bi4Ti3O12 nanoflakes (Pd/BTO NF) were constructed to investigate the photo-excited charge separation, O2 activation and the generated reactive oxygen species (ROS) in dictating NO removal. Results showed that the depolarization field of ferroelectric BTO NF significantly promoted bulk charge separation, leading to boosted NO removal reaction kinetics (10 times higher) for Pd/BTO NF comparing with Pd/TiO2. Revealed by electronic paramagnetic resonance and radical scavenging tests, it is observed that the primary O2 activation species differed among Pd, Ag and Pt supported BTO NF photocatalysts, which resulted in different selectivity. The underlying mechanism of NO photo-oxidative conversion pathway was studied by in situ diffuse reflectance infrared Fourier transform spectroscopy. This work illustrate that metal/ferroelectric interfaces can be tuned to obtain differing O2 activation species, and notable selectivity changes in photocatalysis mediated environmental remediation reactions.
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Elsevier