查看更多>>摘要：Electron generation, transfer and utilization in photocatalytic reduction reactions jointly govern the solar-to-chemical conversion efficiency. In natural photosynthesis, the ultrathin thylakoid membrane loads numerous pigments and proteins for light harvesting and electron transfer, which also integrates ferredoxin-NADP~+ reductase bearing molecule hydrides for electron utilization in NADPH regeneration. Inspired by this, herein, conjugated polymer nanolayer coordinated with (Cp*RhCl2)2 (CPNL-Rh) is developed through a topological and chemical engineering strategy to synergistically intensify electron generation, transfer and utilization for NADH regeneration. Specifically, the triazine moieties well distributed in CPNL-Rh largely harvest visible light to generate electrons. The electrons are rapidly transferred to Rh cocatalyst through CPNL. Rh cocatalyst finally accepts electrons and protons in solution to form molecule hydrides for implementing NADH regeneration. The turnover frequency of CPNL-Rh for NADH regeneration reaches 44.8 h~(-1), among the highest value ever reported and -346% higher than that of bulk CP with free Rh cocatalyst.
查看更多>>摘要：TiO2 nanofiber membranes were prepared by calcinating the electrospun TiO2 nanofibers precursor. Sample calcined at 400 °C (T400) exhibited high CO2 to CH4 conversion efficiency (55.17 μmol · g~(-1) · h~(-1)) and electron selectivity (98.3%) under simulated sunlight. In-situ DRIFTS and the calculated Gibbs free energy revealed CO* to be a major intermediate with the formation of COH* intermediate being the rate-limiting step. The considerable CO2 photoreduction behavior obtained on T400 sample can be attributed to the following causes: (1) the existence of surface OVs gives the change in electronic structure by upshifting CB position to be capable of CO2 photoreduction;; (2) the surface Ti terminals acted as reaction sites, resulting in the accumulation of CO* intermediates to continually produce CH4 with the support of sufficient electrons. These results lay the foundation for advancing the mechanistic insight on CO2 photoreduction and its selectivity to CO2 to CH4.
查看更多>>摘要：In this study, we report a novel self-supported electrode consisting of ceria/molybdenum carbides composite microrods with adjustable crystalline phases and abundant heterostructures on carbon cloth (CeO2/MoxC/CC). The optimized CeO2/α-MoC/β-Mo2C MRs/CC electrode exhibits very low overpotentials of 22 and 29 mV at 10 mA cm~(-2) for hydrogen evolution reaction (HER) in alkaline freshwater and seawater, outperforming most of the reported molybdenum carbide-based electrocatalysts. Meanwhile, it could maintain long-term stability for over 100 h at a large current density of 1000 mA- cm~(-2). Theoretical study and experimental results reveal that the synergistic effects of α-MoC, β-Mo2C, and oxygen vacancy-rich CeO2 can effectively promote the dissociation of water molecules, tailor the d-band electronic structure of MoxC with a thermoneutral hydrogen adsorption free energy, increase the numbers of active sites, and facilitate the vectorial electron transfer, thus achieving an enhanced HER performance. The CeO2/α-MoC/β-Mo2C MRs/CC electrode displays a potential large-scale application in hydrogen generation.
查看更多>>摘要：The ZSM-11 zeolite has been revealed as an undervalued catalyst for the catalytic fast pyrolysis (CFP) of biomass to produce hydrocarbon-rich bio-oil. However, the importance of hierarchical ZSM-11 in bio-oil production is still unknown. Herein, a series of ZSM-11 with varied morphologies, acidities, and secondary mesopores were synthesized and tested as catalysts in the CFP of maize straw. For the morphology series, ZSM-11 with separate nanorods (Nano-ZSM-11) or aggregated nanosized single-crystal (NS-ZSM-11) performed better in bio-oil production than microsized Micro-ZSM-11. Regarding the NS-ZSM-11 series, optimal acidity facilitated the deoxygenation of biomass vapor, while introduced intracrystal mesopores tended to improve bio-oil yield. NS-ZSM-11(20)-0.3 possessing both adequate acidity and coupling inter/intracrystal mesopores led to a satisfactory bio-oil yield (23.6 wt%) and hydrocarbon selectivity (63.6 area%), which were 1.1 and 1.3 times those for Nano-ZSM-11 (bio-oil yield: 22.0 wt%; hydrocarbon selectivity: 47.8 area%), respectively. NS-ZSM-11(20)-0.3 also showed excellent reusability in regeneration-pyrolysis cycles.
查看更多>>摘要：Electrocatalytic oxidation of biomass such as 5-hydroxymethylfurfural (HMF) is a green route to produce value-added chemicals. However, in-depth understanding of the electrocatalytic process is still lacking. Herein, the mechanism of HMF electro-oxidation was studied by operando surface-enhanced Raman spectroscopy (SERS) coupled with an Fe~(3+) probe. A multicomponent platform consisting of titanium plates integrated with a gold film and uniform nickel, cobalt and copper nanoparticles (NPs) was employed as an electrode as well as a SERS substrate, enabling operando SERS study on the electrocatalytic process with simultaneous evaluation on catalytic activity and visualization on the variations of active sites. Fe~(3+) was intentionally added into the electrolyte as a probe to correlate the nature of active sites with catalytic activity and product selectivity in virtue of its strong interaction with the active sites of the electrocatalysts. Electrodes integrated with Ni and Cu NPs exhibited excellent HMF oxidation performance but their activity were suppressed by adding 1 ppm Fe~(3+). Conversely, the activity towards water oxidation was significantly enhanced by Fe~(3+) addition. Fe~(3+) inhibits the oxidation of Ni~(2+) to Ni~(3+) and promotes the formation of more CuO and Cu~(III). Cu~(III) is better active sites for water oxidation. The presence of Fe~(3+) also inhibits the transformation of Co~(3+) to Co~(4+), but it has no pronounced effects on HMF oxidation performance. A highest 2,5-furandicarboxylic acid yield (94.0%) and a maximum HMF conversion (98%) are obtained from the electrode integrated with Cu NPs at a potential of 1.47 V. HMF oxidation on Cu NPs follows the aldehyde oxidation pathway, which is not affected by Fe~(3+) addition. This work could afford a feasible route to explore mechanisms of electrocatalytic processes.
Christos ChatziliasEftychia MartinoConstantinos G. Vayenas
9页
查看更多>>摘要：Low temperature operation of Solid Oxide Fuel Cells (SOFC) typically provides limited and insufficient power for practical applications. The present work demonstrates how this limited power can be utilized effectively for the promotion of a catalytic reaction taking place on a catalyst electrode with minimal energy consumption and environmental impact. A novel design of a low-temperature SOFC reactor is reported and utilized for the electrochemical promotion of CO2 hydrogenation, a reaction of both environmental and industrial importance. The power demand for the enhancement of the catalytic reaction rates is produced in situ by the cell during the parallel oxidation of hydrogen which acts both as a reactant and as a fuel. The results of the present study pave the way for the utilization of Electrochemical Promotion of Catalysis (EPOC) in a wireless configuration, using exclusively the internal power of low temperature, low pressure, SOFCs.
查看更多>>摘要：Single-crystalline transition metal oxide thin film has been employed to perceive the fundamental functions of electronic structure and charge transfer processes in water splitting processes. However, the surface area enlargement and strain tunabilitv in a single-crystalline transition metal oxide are restricted in conventional epitaxy. In this study, we report the oxygen evolution reaction (OER) enhancement by a stack of multilayer SrRuO3 featured single- crystallinity, flexibility, and stackability. The controllable stack of multiple cylindrical SrRuO3 for surface enlargement in a magnitude of order and the emergent electronic structure transition, from t_(2g)(3↑, 1↓) to t_(2g)(3↑)eg(1↓), of Ru efficiently enhances the OER performance, the overpotential can be reduced by ～74 % and ～78 % in KOH and HClO4 respectively at 5 mA/cm~2. Our study provides an approach for fine manipulation of single-crystalline freestanding oxide morphologically, and an efficient strategy aiming at the extreme enhancement of the electrochemically active surface area and the electronic structure engineering by strain.
查看更多>>摘要：Selective electro-oxidation of glycerol to value-added chemicals has attracted much attention both for the upgrading of biodiesel industry and the coupled electrolytic hydrogen production. Here we report Pt nanoparticles decorated, Fe- and N co-doped carbon nanotube (Pt/FeNC) catalyst for the selective electro-oxidation of glycerol to tartronate, one of the valuable chemicals used in pharmaceuticals. In a high concentrated glycerol solution of 5.0 M, the Pt/FeNC catalyst reaches the glycerol conversion of 94% and tartronate yield over 47% at 0.9 V vs. RHE, equivalent to a tartronate production rate of 1182 mmol/h/gPt, about 20 times of the highest value ever reported in a batch electrocatalytic reactor. The valence band analysis and kinetic experiments reveal that the FeNC mediates the adsorption behavior of the glycerate intermediate on Pt surface, and promotes the glycerate-to-tartronate oxidation. Moreover, the anchoring effect of FeNC ensures the stable catalytic performance for ten cycles.
查看更多>>摘要：Taking advantage of the inherent structure in biomass for attractive chemical synthesis with high atom economy is vital for a sustainable future but remains a great challenge. Herein, we discovered a new route for glycolic acid (GcA) synthesis using various biomass-derived polyols as feedstock with an exceptionally high atom utilization (～93 %). Up to ～90 C-mol% yield of GcA could be achieved, representing the highest value among the state-of-the-art biomass valorization strategies. Strongly certified by in situ experimental tests and multi-scale theoretical calculations, it was identified that dynamical accommodation of the flexible unsaturated dangling-like Cu_(cus)-O bond in Cu2O(111) to polyols drove electron transfer from polyols to Cu_(cus) enabling the precise activation of Cl-H and C2-C3 bonds. These contributions accomplished the complex cascade reactions in polyol transformation throughout chain-sugar as intermediate with notable conformation superiority, thus generating GcA selectively.
查看更多>>摘要：Engineering active and robust catalysts for hydrogen evolution and oxidation reactions (HER and HOR) are of importance for the realization of green hydrogen economy. To make catalysts economically competitive for large-scale applications, even-increasing interests have been shifted to designing nonprecious materials for HER and HOR with active and robust performance. Herein, with the guidance of interface engineering, the monolithic catalyst of Ni-MoO2 heterojunctions on nickel foam (Ni-MoO2/NF) was deliberately fabricated by the in-situ corrosion-growth under hydrothermal condition and following thermal-reduction procedure, which exhibits extraordinary HER and HOR performance, for instance, nearly Pt-like catalytic activities, robust long-term durability even under large current density, and superior Faradaic efficiency in alkaline electrolyte. Coupling with the active urea oxidation catalyst of NiMoO4/NF as anode (treating the hydrothermal product in Ar atmosphere), the assembled overall urea splitting electrolyzer with Ni-MoO2/NF as cathode affords the lower voltage of 1.53 V at 20 mA cm~(-2), and keeps this performance overall 120 h without decay. The systematic physicochemical characterization and electrochemical investigations reveal that the heterointerface-induced charge redistribution, individual electrocatalytic functions, superaerophobic/superhydrophilic electrode surface, and monolithic electrode structure together collaborate to the efficient catalytic activity and stability under larger current density.
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