查看更多>>摘要：? 2022 Elsevier B.V.Photocatalytic oxygen reduction is a promising strategy to generate H2O2 in a low-energy input and more sustainable way. Despite great progress have made in photocatalyst design, the rate-limiting step that poor accessibility of the O2 to photocatalysts in water remains unexplored. Here, we design a solid-liquid-air triphasic interface over a melamine foam to boost the interfacial O2 transportation. A Wenzel-Cassie state coexists in a hydrophobic interface and form a tubular confined space with a thickness of 100 μm, which allows the O2 directly transferred to the photocatalyst from the air, greatly boost the formation of H2O2. In addition, a tubular confined microenvironment formed on the surface greatly enhances oxygen diffusion, and suppressed the unwanted decomposition of H2O2. This surface microenvironment engineering resulted in a 10-fold enhancement in the photosynthesis H2O2 compared to the traditional solid-liquid diphase system, pinpointing the necessary O2 mass diffusion for photocatalytic H2O2 generation.
查看更多>>摘要：? 2022 Elsevier B.V.Achieving high-temperature stability/duration without compromising the activity remains an arduous task in catalyst design, particularly for MoS2 materials. Herein, a robust catalyst with Mo doped Co9S8 nanoparticles anchored on Al2O3 matrix is fabricated, which could selectively convert lignin to arenes with high hydrodeoxygenation activity, selectivity and particularly excellent stability. In the hydrodeoxygenation of diphenyl ether, this catalyst afforded 99.8% conversion and 91.0% yield of benzene at 265 °C for at least 10 reaction runs. The resultant Mo-Co9S8 structure with chemical connection by covalent bonds of Mo-S-Co type on the Co9S8 surface demonstrates strong ability in the adsorption and activation of oxygen-containing substrates, which enables the effective C-O cleavage whilst avoids undesirable hydrogenation of benzene ring. The superior stability and water-resistance at elevated temperature was attributed to the anchoring effect of Al2O3 matrix and “protection” of surface-rich Co9S8 species to the active Mo-Co9S8 center. This strategy provides new sights for the rational design of efficient and stable sulfide catalysts towards the applications in demanding high-temperature reactions.
查看更多>>摘要：? 2022 Elsevier B.V.The development of robust catalysts for selective hydrodeoxygenation (HDO) of fatty acid esters is key for production of the diesel-range alkanes under mild conditions. Here, we report a stable and efficient HDO catalyst (Pd@Alx-mSiO2) that composed of inner uniformly dispersed metallic palladium core and the outer mesoporous silica shell doped with aluminum atoms. Using methyl palmitate as a model compound, Al-modified Pd@mSiO2 catalyst (Pd@Al3-mSiO2) exhibited higher catalytic performance (98% conversion rate and 99% selectivity towards diesel-range alkanes) as compared with the Pd@mSiO2 and conventional Pd/γ-Al2O3 catalysts (35% and 70% conversion rates, respectively) at 260 °C and 3.0 MPa H2. Further, when using vegetable oils such as soybean and palm oils as raw materials, high yields of diesel-range alkanes (> 80 wt%) can be obtained under the mild conditions. The HDO reaction pathway was more dominant than the decarbonylation pathway when the reaction was catalyzed by Pd@Al3-mSiO2 catalyst, thereby reducing the loss of carbon atoms. Detailed characterization (27Al NMR, NH3-TPD, and in situ Py-FTIR) suggests that the incorporation of aluminum atoms brings not only Lewis acid sites, but also Br?nsted acid sites via the formation of Si–OH–Al bonds. The synergy between the metallic Pd, Lewis- and Br?nsted-acid sites is responsible for its high HDO activity under the mild conditions. Additionally, the core-shell structure enables fatty aldehyde intermediate preferentially adsorbed on the aluminum atoms in the outer silica shell and avoids direct contacting with metallic Pd, which inhibits the cleavage of C–C bonds to some extent. On the other hand, due to the protective effect of outer silica shell that inhibits the leaching and agglomeration of metallic Pd, the synthesized Pd@Al3-mSiO2 catalyst showed good stability with a slight loss (conversion decreased from 98% to 90%) over five cycles.
查看更多>>摘要：? 2022 Elsevier B.V.Photocatalytic conversion of CO2 to chemical feedstocks represents an intriguing approach to address the energy and environmental crisis, but faces low conversion efficiencies resulted from unsatisfied light absorption, charge recombination and surface reactivity of traditional semiconductor photocatalysts. Herein, we report stacked graphene/Pd@PtCu nanostructures with atomically thin PtCu shell to overcome above challenges and realize high-efficient CO2-to-CH4 photoreduction. The smart design begins with the excitation of Ru complex with broad visible absorption, which is followed by the smooth movement of photoelectrons via the graphene→Pd→PtCu pathway, and then the highly selective CO2 reduction on the PtCu surface. As the PtCu thickness decreases, the strengthened Pd–PtCu interfacial charge polarization contributes to improved charge separation/migration. Meanwhile, CO2 adsorption on the PtCu surface is ameliorated owing to increased electron accumulation and compressive strain. This work provides a new design for boosting the photocatalytic performance by cooperative surface and interfacial modulations.
查看更多>>摘要：? 2022 Elsevier B.V.Oxidative dehydrogenation of ethylbenzene to styrene is considered to be an eco-friendly process, but suffering from overoxidation of the product to carbon oxides due to uncontrollable oxygen reactivity of the catalysts. Here, we report a boron nitride-supported FeOx (FeOx/BN) catalyst, over which an industrially acceptable styrene selectivity (94%) and productivity (0.9 gST gcat?1 h?1) at the conversion of 60% can be attained under oxygen-rich conditions. Based on the investigation of kinetics, CH3OH-TPD, H2-TPR, and O2 pulse reaction, BN support is found to mitigate the oxygen reactivity of FeOx via the strong interaction between the FeOx clusters and the BOx species stemmed from the BN support, which suppresses the overoxidation of ethylbenzene and styrene to carbon oxides. The catalytic tests and structural characterizations reveal that the redox FeOx species initiate the dehydrogenation and then quinone/carbonyl sites on the newly formed coke deposition over FeOx/BN catalyst leads to the increase of activity during the induction period. With the aid of the FeOx and BOx species, the balance between coke deposition and its gasification rates was achieved under oxygen-rich conditions, guaranteeing stable styrene selectivity and productivity.
查看更多>>摘要：? 2022 Elsevier B.V.It is an efficient strategy to replace sluggish water oxidation with a thermodynamically more favorable reaction, electrochemical selective conversion of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA), to promote hydrogen production. High selectivity and Faradaic efficiency (>99%) for the conversion of HMF to FDCA and simultaneous hydrogen production were achieved under 220 mV overpotential on NiCo2O4 electrode. The addition of HMF decreased the anode overpotential, and the amount of generated hydrogen through coupling with HMF oxidation is 8.16 times higher than that of water splitting. Operando Raman identified that NiOOH as the main active species for selective electrooxidation of HMF to FDCA. Operando EXAFS demonstrates that the crystal-strain induced formation of NiOOH from Co–Co bond and such a crystal strain could be further enhanced by the electric field for the in situ formation of more NiOOH. The accelerated reaction pathway was confirmed by operando electrochemical infrared (EC-IR) and DFT calculations.
查看更多>>摘要：? 2022 Elsevier B.V.Electrocatalytic hydrogenation of CO2 has become particularly promising to address the grand issues of global warming and energy crisis. Herein, we report simultaneous increase of conductivity, active sites and structural strain of copper selenide nanosheets by nitrogen (N)-injection (N-CuSe), resulting in significant improvement in CO2 electroreduction. At the applied potential of ?1.1 V vs. reversible hydrogen electrode in CO2-saturated 0.5 mol L–1 KHCO3, the N-CuSe delivers a current density of ～46.7 mA cm–2, 3.1-folds as that of the pristine CuSe. A high production yield of liquid products containing formate (~22.1 mg h?1 cm?2), acetate (~1.2 mg h?1 cm?2) and ethanol (~1.0 mg h?1 cm?2) is achieved by N-CuSe, which is over 11-folds as that produced by the pristine CuSe. Such a facile strategy simultaneously enhancing conductivity, active sites and structural strain holds great promise on promoting catalysts for a big variety of reactions, not limited to CO2 electroreduction.
查看更多>>摘要：? 2022 Elsevier B.V.The development of highly active and stable bifunctional catalysts toward overall water splitting at large current densities through delicate control of composition and structure is a challenging work. Herein, we combined the Ru-doping of NiCo2O4 spinel (NCO) and the surface modification with Ru nanoparticles through rational design and controllable fabrication (NCRO) as a dual modification method to markedly enhance the overall water splitting. Benefiting from the structure advantages, the synergistic electronic effects and optimal binding strength of the reaction intermediates, the NCRO exhibited excellent performance for both hydrogen evolution reaction and oxygen evolution reaction in alkaline media. The density functional theory calculations suggest that the dual modification could enhanced water dissociation ability, optimized the adsorption energy of reaction intermediates and altered the energy level of the d band center.
查看更多>>摘要：? 2022 Elsevier B.V.Surface re-construction was a common phenomenon for non-oxide compound electrocatalysts in anodic oxidation reaction in alkaline electrolyte but surface deactivation arising from excessive oxidation/hydroxylation was critical hindrance to the long-term stability. Herein, a unique anode-cathode interchangeable electrocatalysis strategy is proposed for methanol upgrading reaction (MUR) and hydrogen co-generation in membrane-free electrolyzer. A periodical electrolysis is taken place for the Ni3S2/CNTs electrode at positive/negative currents over time. Compared with the traditional chronopotentiometry mode, the MUR-HER coupled reactions by periodically switching anode/cathode per hour present an excellent long-term stability at high current densities of ± 100 mA cm?2, in which the Faradaic efficiencies for both H2 and value-added formate are greater than 95%. Substantial experimental results and deep theoretical DFT studies signify that the successful application of this strategy is mainly due to the reversible modulation of oxidation/hydroxylation status on Ni3S2 surface, which effectively prevent the surface active structures of electrocatalysts from over-oxidation.
查看更多>>摘要：? 2022 Elsevier B.V.The addition of transition metal dopants into metal oxide nanoparticles (MO NPs) is an universal strategy to engineer the electronic and chemical properties of NPs. Although doping phenomena strongly rely on interactions with compositional and electronic degrees of freedom, fully understanding the site-specific doping behavior in the lattice framework of MO NP on atomic scale remains challenging. Here, we directly resolve the atomic site-selective (substitutional or interstitial) doping behaviors of Cr and Fe in SnO2, revealing their different roles in photocatalytic activities. Atomic-resolution microscopy combined with spectroscopy reveals two contrasting doping behaviors: Cr3+ substitutes for Sn4+ associated with the formation of oxygen vacancies, whereas Fe3+ occupies interstitial sites accompanied by lattice strain. Theoretical calculations indicate that substitutional dopant-vacancy cooperation and interstitial dopant-strain coupling can be energetically favorable routes for enhancing catalytic properties. Our results provide fundamental insights into atomic-scale doping mechanisms and engineering strategies for high-performance doped MO NPs.
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