查看更多>>摘要：The selective reduction of carbon dioxide (CO2) as the primary component of greenhouse gas, remains a significant challenge in photocatalysis. Here, we present a novel strategy of preparing highly selective and stable heterostructure photocatalysts, which simultaneously contain oxygen and nitrogen vacancies. Synergistic catalysis effect originated from Nb2O5 with oxygen vacancies and nitrogen-rich vacancies of metal-free catalytic (g-C3N4) substrate leads to excellent photocatalytic reduction performances. The as-prepared photocatalysts exhibit outstanding capacity of selective reduction of CO2 with yields of CH4 16.07 μmol g~(-1) and CO 0.89 μmol g~(-1) after 5 cycles. Furthermore, the CO2 reduction mechanism is confirmed through density functional theory (DFT) calculation and in-situ technology in detailing. This indicates that the heterojunction surface has a lower free energy barrier for CO2 reduction compared with the pristine sample surface. This new strategy may exploit a vital application of dual-vacancy heterostructure in environmental catalysis.
查看更多>>摘要：Charge separation and transfer from bulk to the redox sites of surface limits the photocatalytic process. Herein, we prepared a novel NiSeS cocatalyst with Mi-Se dual vacancies to construct NiSeS/ZnSe heterojunctions. The optimized NiSeS/ZnSe photocatalyst exhibits a high photocatalytic H2-evolution rate of 18.32 mmol g~(-1) h~(-1) which is 107.8- and 10.2- fold higher than that of pristine ZnSe and 1% Pt/ZnSe, respectively. A high apparent quantum yield value of 50.77% was achieved at 420 nm. The photocatalytic H2 evolution activity of NiSeS/ZnSe is better than most of the state-of-the-art ZnSe-based photocatalysts. The Ni-Se dual vacancies induce a local polarization electric field, which accelerates the surface charge transfer and reduces the reaction barrier in the photocatalytic process. This work provides a feasible approach to introduce dual vacancies and the surface local polarization over photocatalysts for high-performance photocatalytic H2 production.
查看更多>>摘要：Metallic nanomaterials with multidimensional defects are promising for electrocatalysis, whereas exploring facile approaches to synthesize such materials with peculiar structure remains challenging. Here, we firstly synthesized Ru nanoparticles with abundant stacking faults (SFs) combining ultrafast heating with rapid quenching. The close-packed planes of perfect hexagonal closed-packed partially transform into face-centered cubic in the SFs region. It requires 196 mV and 35 mV to drive hydrogen evolution reaction and oxygen evolution reaction under 10 mA/cm~2 current density, prominently expedites overall water splitting with 1.51 V in acid. Theoretical calculations demonstrate the performance is originated from synergistic effect of the SFs and induced continuous strain field, among which the dominant compressive strain attenuates crystal field splitting effect of Ru sites, thus enhancing the electron transfer of Ru sites. The excellent inter-orbital p-d transfers determine strong electronic activities for boosting OER performance. This work provides insights for rational design of catalysts with defective structures.
查看更多>>摘要：Converting nitrate to ammonia (NH3) with the use of electricity produced from renewable energy provides an alternative and sustainable route for NH3 synthesis under ambient conditions. However, due to die complex mechanism involving eight electrons and nine protons transfer processes in nitrate-to-ammonia conversion, reactions run with Cu-based catalysts for NH3 often exhibit limited selectivity and yield. Here, we report a single-atom Ni-alloyed Cu catalyst that exclusively converts nitrate into NH3 with a maximum Faradaic efficiency of ～100% and a yield rate of 326.7 μmol h~9-1) cm~(-2) at - 0.55 V versus reversible hydrogen electrode (RHE). X-ray absorption fine structure evidence and density functional theory calculations reveal that the activated single Ni atom on the Cu catalyst regulates the third protonation step of the electrocatalytic nitrate reduction reaction (eNO_3~-RR) and increases the interaction between the Ni atom and the crucial NOOH~* intermediate, thus decreasing the limiting potential and inhibiting byproduct formation. A rough estimation suggests that die price of fertilizer produced by this single-atom alloyed catalyst through the eNO_3~-RR is competitive with the Haber-Bosch process.
查看更多>>摘要：Development of efficient electrocatalysts requires construction of catalytic surfaces with moderate H adsorption energy. Here, we address this challenge by Br-induced formation of P-poor defective nickel phosphide and show that the H adsorption energy can be optimized by regulating the vacancy concentration. We show that when such defective Ni_(12)P_(5-x)Br_x nanoparticles are distributed on the surface of Ni2P nanosheets (Ni_(12)P_(5-x)B_rx/Ni2P NS), excellent catalytic activity for water splitting is obtained in alkaline media. Density functional theory computations revealed that Br doping induce the formation of a P-poor nickel phosphide with vacancies, leading to an optimal H adsorption strength with a volcano-type relationship. This is the best reported for a non-precious metal phosphide at present: the overpotential for HER is 18 mV at 10 mA cm~(-2) and 155 mV for OER. This leads to an exceptionally low cell voltage requirement of only 1.44 V to drive overall water splitting in an alkaline electrolyzer.
查看更多>>摘要：To overcome slow kinetics of oxygen reduction/evolution reactions (ORR/OER), the development of bifunctional electrocatalysts remains a huge challenge. FeCo alloy as an active-species usually suffers from its poor catalytic stability by easy corrosion. Here, we synthesize a core (FeCo)-shell (carbon) alloy anchored on nitrogen-doped porous carbon-nanosheets (FeCo/NUCSs) via a self-growth strategy. FeCo/NUCSs (140 m~2 g~(-1)) exhibits promising half-wave potential (E_(1/2) =0.89 V) and methanol tolerance for ORR. Prussian blue analog-derived carbon shell protects binary active-sites (Fe-N_x/Co-N_x) on FeCo core to stabilize ORR activity. FeCo/NUCSs also displays a higher OER activity (overpotential of 300 mV) than RUO2, due to generation of highly-active FeOOH/CoOOH species on FeCo alloys as indicated by in situ X-ray diffraction. Assembled Zn-air battery (ZAB) exhibits promising open-circuit voltage of 1.51 V, specific capacity of 791.86 mA h g~(-1), and durability (102 h). This novel bimetallic alloy-based catalyst provides an interesting option for design of durable oxygen-electrocatalysts for ZAB.
查看更多>>摘要：Hydrogen peroxide (H2O2) electrosynthesis through oxygen reduction reaction (ORR) provides an environmentally-friendly alternative to the traditional anthraquinone process. While most studies focus on the original construction of active sites in electrocatalysts, it is also necessary to optimize the microenvironment in the dynamic catalytic process. Here, we proposed a pulse-induced strategy to achieve the in-situ regulation of active sites and interface microenvironment in ORR process, enabling a 210 % leap in H2O2 yield and a 74 % increase in Faraday efficiency. A series of operando measurements revealed the stabilization effect on the catalyst morphology and oxygen-containing functional groups distribution, and the activation effect on the basal defect sites to strengthen the interaction with ~*O2 and ~*OOH. Density functional theory calculations were further employed to reveal a unique ORR reaction pathway which decoupled die proton transfer and electron transfer process in pulsed electrocatalysis, providing new insights into the origin of ORR activity and selectivity.
查看更多>>摘要：A low-cost, high-performance catalyst for phenol steam reforming (PSR) at low temperature was prepared by introducing waste coal ash into Co/Al2O3. The optimized content of coal ash in the catalyst were ranged from 50 to 65 wt%, presenting over 97% phenol conversion and 92% H2 yield at low temperature of 450 °C. The stability for the best catalyst with an ash content of 50 wt% exceeded 85 h. Two-step reduction of Co3O4 to Co~0 via CoO was identified by in-situ XRD. DFT calculations showed that phenol adsorption and decomposition were preferred on the FeCo bimetal surface rather than the single Co surface. H2O adsorption and dissociation fascinated on the CaO incorporated Al2O3 surface. Both Fe and Ca in the coal ash improved the catalyst performance in PSR at low temperature. This work gives an opportunity to solve the drawbacks of high reaction-temperature and low catalyst-stability in PSR, and furthermore benefits to get a deep insight into the reaction mechanism of PSR over the catalyst.
查看更多>>摘要：In this study, reactive oxygen species (ROS)-mediated antibacterial activity with high efficiency in the dark was achieved by modulating the active sites of MIL-101(Fe) nanoparticles. The ROS production over x-MIL-101(Fe) nanoparticles was intensively enhanced by tuning the unsaturated iron sites (Fe~II/Fe~III, the ratio was marked as x %). Electron paramagnetic resonance (EPR) analysis confirmedmore ROS generation on x-MIL-101(Fe) surface than that on MIL-101(Fe), due to more electrons shifting from benzene rings to Fe~II/Fe~III sites. Among all samples, 8.9-MIL-101(Fe) displayed the highest inactivation efficiency (> 99.99%) against Escherichia coli within 2 h in the dark. ROS reacted with cell wall components to generate carbon-centered radicals via H abstraction, leading to the disruption of cell wall, intracellular ROS, and DNA damage. Antibacterial performance of 8.9-MIL-101(Fe) in air filters indicated 8.9-MIL-101(Fe) can be applied to prevent the spread of airborne pathogens. The results are promising for the ambient antibacterial application of MOF materials.
查看更多>>摘要：We present a chainmail catalyst (N-doped carbon nanotube-conftned FeMn nanoparticles, FeMn@NCNT) for activation of peroxymonosulfate (PMS) to eliminate organic micropollutants (OMPs). Complete removal of 50 μM 4-chlorophenol (4-CP) was achieved in 7 min. Radical quenching tests and electron paramagnetic resonance suggested that an electron transfer process (ETP) dominated the degradation of pollutants, while ·OH and ·SO_4~-were the secondary oxidants. In an upgraded galvanic oxidation system, the surge of current and the decrease of in-situ cathode potential after adding 4-CP indicated the electron shuttle rather than adjacent transfer mechanism dominated ETP. A novel spray-crosslinking method was introduced to deposit powder FeMn@NCNT on a commercial ceramic membrane. The coated membrane exhibited a negligible decrease of water flux, excellent mechanical stability and outstanding OMP elimination performance. This study provides new insights into ETP and advances the application of powder catalysts in combined filtration/oxidation water treatment processes.
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