查看更多>>摘要：Enhancing the separation of photogenerated electrons and holes is crucial for improving the photocatalytic performance of carbon nitride(CN).In this work,a ECN-Vn/C photocatalyst with unique three-dimensional nanostructure was constructed by exfoliation of multilayered CN,followed by introduction of nitrogen vacancies and intercalation of carbon species between the exfoliated CN nanosheets.Compared to pristine CN,ECN-Vn/C photocatalyst has stronger light absorption,more surface active sites,and better separation efficiency of photogenerated carriers.Formation of dual built-in electric fields in ECN-Vn/C,which result from the synergy of nitrogen vacancies and intercalation of carbon species,promotes the migration of photogenerated electrons and holes in opposite directions,and greatly accelerates the separation efficiency of these carriers.Photocatalytic hydrogen production activity of ECN-Vn/C photocatalyst was 12.1 times higher than that of pristine CN.The synergy between nitrogen vacancies and intercalation of carbon species provides a new strategy for designing more efficient CN-based photocatalysts.
查看更多>>摘要：Multicomponent heterogeneous catalysts present excellent catalytic performance attributed to the synergistic effect of multi-sites.Nevertheless,identifying the composition of the multi-sites and exploring the synergistic catalytic mechanisms for the multiple active sites in electrocatalytic CO2 reduction reaction(CO2RR)still lack intensive study.This work regulates the chemical composition of Cu-based nanoreactors readily by adjusting the geometrical morphology of metal-organic frameworks precursor.The obtained cuboctahedron nanoreactor containing CU-N4/Cu2O/CU multiple active sites exhibits excellent CO2RR selectivity towards deep reduction product(80%)with high current density.Moreover,the tandem catalytic mechanism of multicomponent active sites has been studied intensively.The CO2 molecule is firstly reduced in CU-N4 sites to form CO and then the CO is transfered to Cu2O/Cu sites for further deep reduction.The high concentration of CO provided by CU-N4 sites decreases the free energy of rate-determining step for CH4 products in Cu2O sites.This work provides a promising direction for designing and synthesizing multicomponent Cu-based tandem catalysts to access high efficiency and selectivity in the electrocatalytic CO2 reduction reaction.
查看更多>>摘要：Hydrogen peroxide(H2O2)production has long been one of the key technologies in modern chemical industries.Conventional methods for large-scale H2O2 production are challenged by either high-energy-consumption or harsh reaction conditions.Here,we demonstrate a strategy to produce H2O2 with high yield catalyzed by organophotocatalyst using only H2O and O2 as the raw material without the assistance of additional scavengers.Our strategy features the design principle of the organophotocatalyst and a phase-transfer photocatalytic process under ambient condition.We show that both photocatalytic reduction of O2 and photocatalytic oxidation of H2O are responsible for H2O2 production in this phase-transfer photocatalytic process,and the solvent permittivity and intermolecular interaction between O2 and organophotocatalyst are the keys to achieve high efficiency.The photocatalytic H2O2 production rate in the system reaches 9000 jimol g~(-1)h~(-1)in the initial stage under ambient condition,and the apparent quantum efficiency(AQE)was ca.8.2% based on the 595 nm wavelength.This work brings new insight to H2O2 production in a distinct mechanism that may inspire the development of low-energy consumption and cost-effective H2O2 production through photocatalysis.
查看更多>>摘要：The performance of nickel supported on lanthana-modified hydroxyapatite(HAP)catalysts is investigated in the CO2 methanation.The addition of La(1-6.6 wt%)leads to a surface enrichment following a sequential multilayer deposition model.Moreover,La addition systematically improves the dispersion of Ni particles and their reducibility,which in turn increases spectacularly the amounts of basic sites and their thermal stability.Such physicochemical changes impact positively on the activity of the catalysts in CO2 methanation.The estimated turnover frequency(TOF)suggest that the small Ni particles are the most efficient.The latter seem to provide a large density of very active defects on Ni-La2O3 interface.The optimized catalyst proves to be highly resistant to deactivation during 100 h time-on-stream(TOS).The samples were also assayed as dual function materials(DFMs)for CO2 adsorption and methanation.A scheme is proposed to describe the different steps involved in a CO2 adsorption/hydrogenation cycle.
查看更多>>摘要：In order to improve the carrier transfer driving force and separation efficiency,Oy-BiOBr/Cu_(2-x)S high-low junction with double defects(Oxygen vacancy and Copper vacancy)was successfully prepared by a facile two-step solvothermal in situ growth technique.OyBiOBr/Cu_(2-x)S-0.2 showed the highest hydrogen evolution rate(509.75 μmol·cm~(-2)·h~(-1)),which was 12.45,6.94 and 3.44 times that of pure BiOBr,Ov-BiOBr and BiOBr/Cu_(2-x)S composite,respectively.Obvious free radicals(·OH and O2)were observed in the dark state for the first time.Theoretical and experimental results demonstrate that the charge imbalance within Ov-BiOBr/Cu_(2-x)S intensifies after the introduction of the double defects,resulting in enhanced interfacial polarization phenomena.Boosted photoelectrochemical hydrogen evolution activities were achieved with the synergistic effect of the internal electric field and polarization electric field.This study will lay a scientific and experimental foundation for the preparation of high-performance photoelectrochemical anode materials with double defect heterojunction.
查看更多>>摘要：Electrocatalytic hydrogen evolution reaction(HER)in acidic solution using Co-based oxides is extremely difficult due to their instability.Herein,we report a hollow carbon sphere-supported Pt/CoOx(Pt/CoOx-HCS)electro-catalyst for active HER in 0.5 M H2SO4 solution.Microstructural and electrochemical evaluations confirm the dissolution of major CO3O4 in Pt/Co3O4-loaded HCS(pre-Pt/Co3O4-HCS)and the steady existence of remaining CoOx in Pt/CoOx-HCS after 3000 cyclic voltammetry(CV)cycles(Pt/CoOx-HCS-3000).The Pt/CoOx-HCS-3000 exhibits a pretty high turnover frequency(TOF)of 24.87 H2 s~(-1)at 100 mV overpotential,a low overpotential of 28 mV at 10 mA cm~(-2),and a large mass activity of 3.59 A mg_(Pt)~(-1)at 30 mV overpotential.The robust stability of Pt/Co(VHCS-3000 is attributed to the strong electronic interaction between Pt and CoOx,preventing the aggregation of the former and the thorough dissolution of the latter.This work provides insights into the design of Co based-oxide electrocatalysts with outstanding acidic performances.
查看更多>>摘要：As a safe and environmentally friendly selective hydrogenation method,catalytic transfer hydrogenation(CTH)has aroused great interest in preparation of high-value-added products from biomass derived resources.Herein,a Cu-based catalyst(Cu/CuAl-MMO-400)was prepared by structural topological transformation of layered double hydroxides(LDHs)precursor,which displayed promising catalytic behavior toward CTH reaction of furfural(FAL)with 2-propanol(2-POL)as the hydrogen donor.Notably,the reaction rate is as high as 0.125 mol g~(-1)h~(-1),which is superior to previously reported non-noble metal catalysts.A combination investigation based on XPS,XANES and Bader charge confirms the co-existence of Cu° and Cu~+ sites on the surface of Cu nanoparticles.Both experimental studies [in situ DRIFTS and isotope labelling MS)and DFT calculations reveal that the Cu°-Cu~+ synergistic effect plays a vital role in determining catalytic behavior: the Cu~+ species acts as both dehydroge-nation and hydrogenation active site; while the Cu~0 site promotes the transfer of H atoms between adsorbed substrates.This work substantiates a Cu~0-Cu~+ synergetic catalysis by establishing structure-property correlation and revealing reaction pathway,which could be extended to other CTH reactions in the upgrading processes of biomass.
查看更多>>摘要：Ni single-atom catalysts(SACs)can perform with the extremely high activity in the activation of the C-H bond,however,deactivation caused by carbon deposition became the main obstacle for commercialization.Herein,Ni/CeO2 SAC was synthesized and employed in dry reforming of methane(DRM)reaction.The oxygen vacancies(OV)with different concentrations were successfully regulated on CeO2 surface by the replacement of Ce~(4+)cation by a smaller-size cation M(M= Mg,Co,Zn).The catalyst with the highest Oy concentration has performed with the highest activity retention and a high turnover frequency of methane(14.5 s~(-1)).During the DRM process,along with the increase of the Oy concentration from 21.9% to 30.8%,the amount of carbon deposition decreased by 50%.The effective C-H activation function from Ni SACs and CO2 activation function from Oy were synergistically combined,leading to a high activity of methane conversion and an effective carbon removal process in the OV-SAC catalytic system.This work provides a novel strategy to obtain a robust Oy-SAC catalytic system for efficient and stable C-H activation.
查看更多>>摘要：The reductibility of B-site elements in perovskite(ABO3)structures is one of the paramount factors that promote the in-situ exsolution of metallic nanocatalysts,and the phase transition of the support to a more stable structure under solid oxide cell(SOC)fuel electrode operating conditions.Herein,we develop a highly catalytically active and durable perovskite-based fuel electrode material-La_(0.6)Sr_(0.4)Co_(0.15)Fe_(0.8)Pd_(0.05)O_(3-δ)(LSCFP)-for reversible SOCs.The LSCFP material under the fuel electrode condition is fully transformed into a stable Ruddlesden-Popper phase decorated by bimetallic Co-Fe nanocatalysts.The SOC with LSCFP fuel electrode yielded outstanding performances in both fuel cell(2.00 W cm~(-2))and electrolysis cell(2.23 A/cm~2 at 1.3 V)modes at 850 ℃,with remarkable reversible-cyclic stability.These results clearly demonstrate that the novel LSCFP capable of concurrent phase transition and bimetallic exsolution in the reducing condition is a highly prospective candidate as a bifunctional fuel electrode for reversible SOCs.
查看更多>>摘要：Phosphate modification over semiconductor photocatalyst was an effective route to promote photodegradation of organic pollutants.Studies on promoted O2 adsorption,better charge separation,and free ·OH radicals raised from phosphate modification are clear,whereas O2 activation and the generated reactive oxygen species(·O_2~-H2O2,and ~1O_2)have been ignored.Herein,the hydrogen bond network constructed between BiOCl surface and phosphate weaken the surface Bi-0 bond thus benefit the formation of oxygen vacancy(OVs).OVs not only facilitate the adsorption of organic pollutants but also promote the O2 activation to generate H2O2 and ~1O_2.Another route for ~1O_2 generation relies on the H2O2 reacted with HC10 from lattice chlorine oxidation was demonstrated.The directly attack of surface adsorbed 4-CP via h~+,in addition with the selective oxidation via ~1O_2,synergetically contribute excellent photodegradation performance.This study systematically reveals the O2 activation and ~1O_2 generation for efficient photodegradation over phosphate modified BiOCl.
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