查看更多>>摘要：Electrocatalytic depolymerization of lignin into value-added chemicals offers a promising technique to make biorefining sustainable.Herein,we report a robust trimetallic PdNiBi electrocatalyst for reductive C-O bond cleavage of different lignin model dimers and oxidized lignin under mild conditions.The reduction reaction proceeds with complete substrate conversion and excellent yields toward monomers of phenols(80％-99％)and acetophenones(75％-96％)in the presence of an ionic liquid electrolyte with operational stability.Systematic experimental investigations together with density functional theory(DFT)calculations reveal that the outstanding performance of the catalyst results from the synergistic effect of the metal elements,which facilitates the easier formation of a key Cα radical intermediate and the facile desorption of the as-formed products at the electrode.The results open up new opportunities for lignin valorization through the green electrocatalytic approach.
查看更多>>摘要：As a four-electron transfer reaction,oxygen evolution reaction(OER)is limited by large overpotential and slow kinetics.Here,we in-situ synthesized two-dimensional(2D)Ni-Fe metal-organic framework nanosheets on nickel foam(NixFe-TPA/NF,TPA=terephthalic acid)for oxygen evolution in alkaline and alkaline seawater electrolytes.In 1 M KOH,Ni3Fe-TPA/NF shows a low overpotential(η10)of 189 mV at 10 mA·cm-2 and an ultra-low overpotential of only 260 mV at 500 mA·cm-2.In alkaline seawater,Ni3Fe-TPA/NF still provides impressive OER performance,with an η10 of 265 mV.In-situ Raman characterization results show that the phase transition occurs during the OER,and Ni3FeOOH with more oxygen vacancies is in-situ formed,reducing the OER energy barrier.Density functional theory(DFT)reveals that the synergy between Ni and Fe reduces the energy barrier and accelerates the rate-determining step.In addition,the ultra-thin 2D sheet structure and the close combination of Ni3FeOOH and highly conductive NF support ensure the high catalytic OER activity.Therefore,the surface reconstruction and structural modification strategy can be used to design and prepare high-performance OER electrocatalysts for energy-related applications.
查看更多>>摘要：The electrocatalytic nitrate reduction reaction(NitRR)represents a promising approach toward achieving economically and environmentally sustainable ammonia.However,it remains a challenge to regulate the size effect of electrocatalysts to optimize the catalytic activity and ammonia selectivity.Herein,the Cu-based catalysts were tailored at the atomic level to exhibit a size gradient ranging from single-atom catalysts(SACs,0.15-0.35 nm)to single-cluster catalysts(SCCs,1.0-2.8 nm)and nanoparticles(NPs,20-30 nm),with the aim of studying the size effect for the NO3-to-NH3 reduction reaction.Especially,the Cu SCCs exhibit enhanced metal-substrate and metal-metal interactions by taking advantageous features of Cu SACs and Cu NPs.Thus,Cu SCCs achieve exceptional electrocatalytic performance for the NitRR with a maximum Faradaic efficiency of ca.96％and the largest yield rate of ca.1.99 mgNH3·h-1·cm-2 at-0.5 V vs.reversible hydrogen electrode(RHE).The theoretical calculation further reveals the size effect and coordination environment on the high catalytic activity and selectivity for the NitRR.This work provides a promising various size-controlled design strategy for aerogel-based catalysts effectively applied in various electrocatalytic reactions.
查看更多>>摘要：One-pot tandem catalysis has been regarded as one of the most atomic economic ways to produce secondary amines,the important platform molecules for chemical synthesis and pharmaceutical manufacture,but it is facing serious issues in overall efficiency.New promotional effects are highly desired for boosting the activity and regulating the selectivity of conventional tandem catalysts.In this work,we report a high-performance tandem catalyst with maximized synergistic effect among each counterpart by preciously manipulating the spatial structure,which involves the active CeO2/Pt component as kernel,the densely-coated N-doped C(NC)layer as selectivity controller,and the differentially-grown Co species as catalytic performance regulators.Through comprehensive investigations,the unique growth mechanism and the promotion effect of Co regulators are clarified.Specifically,the surface-landed Co clusters(Cocs)are crucial to selectivity by altering the adsorption configuration of benzylideneaniline intermediates.Meanwhile,the inner Co particles(Cops)are essential for activity by denoting their electrons to neighboring Ptps.Benefiting from the unique promotion effect,a remarkably-improved catalytic efficiency(100％nitrobenzene conversion with 94％N-benzylaniline selectivity)is achieved at a relatively low temperature of 80 ℃,which is much better than that of CeO2/Pt(100％nitrobenzene conversion with 12％N-benzylaniline selectivity)and CeO2/Pt/NC(35％nitrobenzene conversion with 94％benzylideneaniline selectivity).
查看更多>>摘要：Highly evolved multi-enzyme cascade catalytic reactions in organisms facilitate rapid transfer of substrates and efficient conversion of intermediates in the catalytic unit,thus rationalizing their efficient biocatalysis.In this study,pore-ordered mesoporous single-atom(Fe)nitrogen-doped carbon nanoreactors(Mp-Fe-CN)were designed,in which a reasonable pore size was designed as a natural enzyme trap coupled to a simulated enzyme center.A polarity-mediated strategy was developed to obtain atomically dispersed nanoporous substrates,with the finding that polarity-guided engineering of the nitrogen-ligand environment and vacancy cluster defects clearly affects nanoporous activity,accompanied by appreciable mesoporous pore size elevation.The active center and distal N atom coordination of Fe-N4 affect the catalytic process of the nanozyme exposed by density functional theory(DFT),determining the contribution of hybridized orbitals to electron transfer and the decisive step.A cascade nanoreactor-based domain-limited sarcosine oxidase developed for non-invasive monitoring of sarcosine levels in urine for evaluation of potential prostate carcinogenesis as a proof of concept.Based on the design of surface mesoporous channels of nanocatalytic units,a bridge was built for the interaction between nanozymes and natural enzymes to achieve cascade nanocatalysis of natural enzymatic products.
查看更多>>摘要：Design and development of advanced electrocatalysts with high performance and low Pt consumption are crucial for reducing the kinetic energy barrier of the cathode oxygen reduction reaction(ORR)and improving the efficiency of proton exchange membrane fuel cells(PEMFC).In this study,we demonstrate a Pb-modulated PtCo system for efficient ORR,in which the inclusion of Pb in ternary alloys induces dislocation defects due to the significant difference in atomic radius.Dislocation-PtCoPb was confirmed to exhibit significantly higher ORR activity and stability in acidic ORR.In practical PEMFC applications,it outperforms the corresponding commercial Pt/C with a mass activity of 0.58 A·mgPt-1,making it a promising alternative to state-of-the-art Pt-based catalysts.The combination of experimental results and density functional theory(DFT)calculations offers valuable atomic-level insights into the dislocation structures.Pb with a larger atomic radius is located in the lattice stretching region below the dislocation slip plane,forming a structure similar to a Cottrell atmosphere,which reduces the dislocation energy and puts the system in a lower energy state.The Cottrell atmosphere pins the dislocation structure and stabilizes the ternary alloy.By adjusting the amount of added Pb,a moderate level of dislocation density induces a tuned strain effect,thereby enhancing the electrocatalytic mechanism by optimizing the electronic structure of the alloy surface and the adsorption and desorption of oxygen species.This work provides valuable insights into the design and development of lattice dislocation defect structures to trigger strain effects for improving ORR performance.
查看更多>>摘要：Partial oxidation of methane into primary oxidation products with high value remains a challenge.In this work,photocatalytic oxidation of methane(CH4)with high methyl hydroperoxide(CH3OOH)selectivity is achieved using pure titanium oxide(TiO2)without any cocatalyst at room temperature and atmospheric pressure.The CH3OOH production rate can reach up to 2050± 88 μmol·g-1·h-1 at pH ≈ 7.0 with 100％selectivity in the liquid product.The stable reaction cycle can reach more than 30 times.This low-cost system achieves superior CH4 conversion activity and selectivity compared with similar work.The energy of hydrogen peroxide(H2O2)to adsorbed hydroperoxyl radical(*OOH)has a significantly lower reaction energy than conversion to adsorbed hydroxyl radical(*OH)on the(210)surface of the TiO2.The*OOH preferentially combines with methyl radical(·CH3)to form the most energetically favorable CH3OOH.The mild oxidative environment of this system prevents the reduction of CH3OOH to CH3OH or over-oxidation of CH4,which ensures the final CH3OOH with high selectivity and stability.This work provided a low-cost but highly efficient method to achieve partial oxidation with superior selectivity,i.e.,to convert CH4 into high-value chemicals.
查看更多>>摘要：The migration of protons during the oxygen evolution reaction(OER)is a key factor that affects the performance of OER catalysts.To enhance proton transportation,we designed a catalyst based on nickel/iron-pyromellitic acid(NiFe-PMA)prepared by the electrochemical deposition method.This catalyst exhibited a low overpotential of 188 mV at a current density of 10 mA·cm-2,a Tafel slope of 28.2 mV·dec-1,and long-term stability for 30 days with a current of 50 mA·cm-2.We characterized the NiFe-PMA catalyst using various techniques,including Fourier transform infrared(FTIR)spectroscopy,Raman spectroscopy,X-ray photoelectron spectroscopy(XPS),X-ray absorption spectroscopy(XAS),transmission electron microscopy(TEM),scanning electron microscopy(SEM),and inductively coupled plasma-optical emission spectrometry(ICP-OES).Our results showed that NiFe-PMA contains nickel,iron atoms,and both coordinated and uncoordinated carboxylate groups.Additionally,XPS data confirmed that carboxylate ligands could adjust the outer electronic structure of metal ions,resulting in the high valence state of Ni in NiFe-PMA.The result of XAS indicated that the nickel atoms present in the catalyst might be easier to maintain a higher chemical state.Further investigations using kinetic isotope effects(KIEs)and proton inventory revealed that the uncoordinated carboxylic protons played a crucial role in receiving protons during the OER,which promoted the proton transfer of the rate-determining step of the OER.Our novel electrocatalysts provide a new strategy for designing more active and cost-effective catalysts for the OER.
查看更多>>摘要：Stable and efficient single atom catalysts(SACs)are highly desirable yet challenging in catalyzing acidic oxygen evolution reaction(OER).Herein,we report a novel iridium single atom catalyst structure,with atomic Ir doped in tetragonal PdO matrix(IrSAs-PdO)via a lattice-confined strategy.The optimized lrSAs-PdO-0.10 exhibited remarkable OER activity with an overpotential of 277 mV at 10 mA·cm-2 and long-term stability of 1000 h in 0.5 M H2SO4.Furthermore,the turnover frequency attains 1.6 s-1 at an overpotential of 300 mV with a 24-fold increase in the intrinsic activity.The high activity originates from isolated iridium sites with low valence states and decreased Ir-O bonding covalency,and the excellent stability is a result of the effective confinement of iridium sites by Ir-O-Pd motifs.Moreover,we demonstrated for the first time that SACs have great potential in realizing ultralow loading of iridium(as low as microgram per square center meter level)in a practical water electrolyzer.
查看更多>>摘要：There are more challenges for alkaline hydrogen evolution reaction(HER)via simultaneously expediting the electron-coupled water dissociation process(Volmer step)and the following electrochemical H2 desorption(Heyrovsky step).Hybrid amorphous electrocatalysts are highly desirable for efficient hydrogen evolution from water-alkali electrolyzers due to the bifunctionality for the different elementary steps of HER and optimal interactions with water molecules and the reactive hydrogen intermediates(Had).Herein,the synthesis of amorphous hybrid ultrathin(tungsten oxide/nickel hydroxide)hydrate(a-[WO3/Ni(OH)2]·0.2H2O)nanosheets on nickel foam(NF)for efficient alkaline HER is described.The structural and composition features of a-[WO3/Ni(OH)2]·0.2H2O are characterized in detailed.The resulting a-[WO3/Ni(OH)2]·0.2H2O/NF electrocatalyst with the synergistic effect of both hybrid components for the HER elementary steps shows greatly improved the activity and durability for the HER with a low overpotential of-41 and-163 mV at-10 and-500 mA·cm-2,respectively,a Tafel slope as low as-72.9 mV·dec-1,and long-term stability of continuous electrolysis for at least 150 h accompanying by inappreciable overpotential change in 1 M KOH.In the hybrid a-[WO3/Ni(OH)2]·0.2H2O,Ni(OH)2 and WO3 moieties are separately responsible for accelerating dissociative adsorption of water and weakening Had adsorption strength,which is beneficial to the improvement of the alkaline HER activity.
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