查看更多>>摘要：The possible phase transformation of catalysts under reaction conditions brings lots of difficulties in establishing the active phase.Herein,we report a hidden active phase over iron catalyst uniquely for the dehydrogenation of ammonia(NH3).The highest dehydrogenation rate corresponds to an evanescent Fe/Fe4N mixing phase while the nitrogen(N)kept on accumulating and gradually deactivated the catalyst.Density functional theory(DFT)calculations demonstrated that deposition of an N on Fe(100)surface modifies the electronic structure of its surrounding iron atoms,causing a significant reduction of the initial dehydrogenation barrier of NH3.To recover the hidden active phase,ambient-pressure double dielectric barrier discharge(DDBD)plasma was applied to the reaction system in situ to remove the excessive surface N,which yields a pronounced improvement of the catalytic performance.The work demonstrates that hidden active phase in thermal catalysis can be unfolded when the rate-determining step is subdued by applied plasma.
查看更多>>摘要：Alkali metals are used as promoters in a broad range of catalytic reactions involving supported metal catalysts,and the origin of their promotional effects has become one of the fundamental questions in heterogeneous catalysis.However,a thorough understanding of the promotional mechanism is still unclear.Combining experiments and theory,the effects of alkali metals on the reactivity of CO2 methanation reaction over Ru/ZrO2,a crucial reaction for CO2 utilization is explored.The conventionally assumed electron enrichment of Ru is not the decisive factor for the promotion.Rather,Na promotion facilitate the adsorption and dissociation of CO on the local interfacial Ru sites of Ru/ZrO2,which is the key step of CO2 methanation process.The feasible dissociation of CO on the alkali metal promoted Ru/ZrO2 originates from the enhanced electron back-donation from the interfacial Ru sites,which leads to more than an order of magnitude increase in CO2 conversion activity.
查看更多>>摘要：Wastewater remediation using micro/nanomotors is a hot topic,and MnO2 based materials have become fascinating alternatives to rare noble metal-based micro/nanomotors.Herein,we demonstrate facile and large-scale synthesis of Fe-MnO2 core-shell micromotors for antibiotic pollutant removal.Heat-treatment results in a phase transformation of MnO2 with formation of iron oxides and partially exfoliates the MnO2 nanoplate shell structure to promote mobility.The iron-manganese oxide micromotors exhibit an efficient removal of tetracycline antibiotics via a combination of catalytic degradation and adsorptive bubble separation.For the first time,atomic H* was found to participate in the micromotor-assisted degradation process,resulting in optimal Fenton reaction in neutral conditions with a good decontamination performance.Owing to the merits of abundance,magnetic recovery,facile fabrication,good motion,and environmental friendliness,as well as decontamination performance in a wide pH range,these core-shell micromotors demonstrate a promising candidate in practical wastewater treatment.
查看更多>>摘要：Photocatalytic H2O2 generation has drawn growing attention for on-site H2O2 production.However,current photocatalytic systems still need organic electron donor,oxygen aeration,and acidic pH to elevate the production efficiency.We report a crosslinking polymer catalyst constructed by β-cyclodextrin aldehyde and 4-amino-6-hydroxy-2-mercaptopyrimidine to address the above challenges.This novel catalyst achieves an outstanding yield rate of 557.2 μM g~(-1)h~(-1)for photocatalytic H2O2 production in pure water and can maintain its performance over a wide pH range(1-11)without electron donor or oxygen aeration.The mechanism investigation shows that the high generation performance is attributed to the mutual promotion of water photooxi-dation and oxygen photoreduction.Moreover,this catalyst is demonstrated for in situ sterilization in various water bodies under visible light irradiation.The reported polymer photocatalyst addresses some of the obstacles in photocatalytic H2O2 generation,and will promote practical applications of H2O2 generation from solar energy.
查看更多>>摘要：Defect engineering and heterogeneous doping are considered as the effective routes to improve the photo-catalytic activity of MoS2.In this study,tungsten was used to produce sulfur defects and tungsten doping on MoS2 by one step hydrothermal treatment.Tungsten doping not only promotes the formation of sulfur defects,but also accelerates the efficiency of separation and transfer of electron-hole pairs,which enables the samples to maintain high catalytic oxidation activity for a long time.Furthermore,comparative experiments show that sulfur defects can promote the activation of O2 and the formation of more active O2 and OH species.As a result,the W-doped MoS2 exhibited a high removal efficiency of more than 99% of gaseous mercury.In addition,W-doped MoS2 showed good stability,long term durability,enhanced water and sulfur resistance under light illumination.This work provides a novel direction for designing efficient photocatalysts based on transition metal dichalcogenides.
查看更多>>摘要：The regulation of reactive oxygen species(ROS)in photocatalytic processes remains insufficiently explored.Herein,three triazine-based conjugated polymers were designed to regulate ROS by tuning structures.Strong superoxide radical was generated together with hydrogen peroxide through the electron transfer from the photocatalysts to oxygen,when electron donor-acceptor(D-A)structures were constructed in the photocatalysts.By sharp contrast,singlet O2 that was generated via energy transfer was the dominant ROS on the photocatalyst with a symmetric structure.It was demonstrated that the separation of excitons in the D-A photocatalysts was much more efficient.By using the most efficient D-A photocatalyst,phenol was degraded completely within 60 min,and 1351 μmolh~(-1)g~(-1)of hydrogen peroxide was generated simultaneously.The photodegradation performance and the photosynthesis performance both ranked among the highest ones.The regulation of ROS by tuning the structures of photocatalysts opens new prospects for the design of efficient photocatalysts at the molecular level.
查看更多>>摘要：The formation of a crystalline-amorphous(c-a)interface by modulating the crystallinity of the material is a promising strategy for oxygen evolution reaction(OER).Therefore,a similar element substitution approach is reported in this study to regulate the catalyst's crystallinity.Adjustment of the cobalt content in NiFe layered double hydroxide(LDH)by the solvothermal method enables the control of c-a interfacial site of the material.In 1 M KOH,the as-obtained Co_(1.98)-NiFe LDH exhibited a low overpotential of 236 mV to achieve 20 mA cm~(-2).It also showed excellent stability,operating steadily at high current densities for 96 h without significant degradation in 1 M KOH or alkaline artificial and natural seawater electrolytes.Therefore,the OER activity of the catalysts was improved while ensuring structural stability.We believe that this method will provide new insights and perspectives for the development of highly efficient and stable OER catalysts.
查看更多>>摘要：Water is considered as a promoter for the CO oxidation over Au catalysts but experimental evidence of how adsorbed H2O may influence the CO oxidation is scarce.In this study,Au/BN catalysts prepared by deposition method are subjected to calcination at different temperature.Increasing calcination temperature results in more Au particles distributed on BN basal plane,increased water affinity,increased defects on BN,and altered CO oxidation activity.All catalysts exhibit two CO adsorption bands at high relative humidity which are attributable to CO_(ad)on Au~0 and CO(H2O)n species,although only a blue-shifted CO_(ad)is found at nominal dry condition.The turnover frequency is found to correlate with H2O physisorption,with a volcano-shape dependency on surface density and first-layer physisorption enthalpy of H2O_(ad).How the physisorbed H2O may influence CO oxidation over Au/BN is discussed and it implies that(H2O)_(n,ad)cluster is involved in CO activation.
查看更多>>摘要：In the ammonia borane(AB)hydrolysis reaction,overcoming the weak activation of H2O by metal catalysts can be achieved by introducing transition metal oxides(TMOs)for catalyst active-sites design.Herein,we uncovered that oxygen vacancy(Vo)-attired Cu/Cu_(0.76)CO_(2.24)O4 dual-active-sites catalysts significantly increase the hydrogen production rate of AB hydrolysis.The turnover frequency of Cu/Cu_(0.76)CO_(2.24)O4-VO dehydrogenation in 0.10 M NaOH can reach 50.33 mol_(H2)/(mol_(cat)·min),which is 45.9 times that of metal Cu.By means of a joint experimental and computational study,the VO defects promote the formation of electron-rich surface of Cu/Cu_(0.76)CO_(2.24)O4,and the Cu also enriches the surface electrons due to the strong interaction with TMOs,which enhances the activation of O-H and B-H bonds,respectively,and significantly accelerates the rate-determining step of the reaction.This work demonstrates the important role of constructive defects in regulating surface electrons of dual-active-sites catalysts on the performance enhancement and provides a broader idea for the design of excellent AB hydrolysis catalysts.
查看更多>>摘要：Engineering the adsorption and dissociation of molecules on dual-active sites at interface is an integral constituent for rational design of high-efficient catalysts.Herein,we describe a unique atomic-bridge structure in B-Co-P(namely Co-B and Co-P)dual-active sites on boron nitride nanosheets to stimulate activity toward boro-hydride hydrolysis.The formation of atomic-bridge structure in B-Co-P dual-active sites is contributed to the Local P-inducing Strategy(LPiS).The catalyst exhibits superior kinetics(turnover frequency of 37 min~(-1))with favorable stability during ammonia borane hydrolysis.Both experimental investigation and theoretical calculations reveal the key effects of atomic-bridge structure in B-Co-P interfacial dual-active sites on tailoring the electron density of Co species and reducing the energy barrier of reaction between ammonia borane and water molecules.This discovery is anticipated to furnish an impactful strategy to rationally design novel performance-oriented advanced catalysts for heterogeneous catalysis.
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