查看更多>>摘要：Efficient conversion of CO2 is of great significance for sustainable supply of chemicals and fuels. While Co-based catalysts are known to be effective for CO hydrogenation in Fischer-Tropsch synthesis, they work very differently in CO2 hydrogenation. This study reveals a crystallographic dependence of reaction pathways for CO2 hydrogenation on Co catalyst showing a new type of structure sensitivity and structure-activity-selectivity relationship for CO2 conversion to chemicals and fuels. The experimental work on CO2 conversion including steady-state isotopic transient kinetic analysis (SSITKA) using 13C-labeled CO2 shows a preferential CH4 formation over HCP-Co but dominant CO formation over FCC-Co. The density functional theory calculations indicate that CO2 does dissociate directly into chemisorbed CO* and O* on both HCP-Co and FCC-Co, but the CO* intermediates on HCP-Co prefer to be hydrogenated to form CH4 whereas the CO* on FCC-Co preferentially desorb to form CO. The significantly altered adsorption strength of CO* due to the presence of chemisorbed O* and CO2* species on the catalyst surface is responsible for the mechanistic disconnection in product selectivity between the CO2 and CO hydrogenation over Co catalysts. This study also shows that the addition of K to Co diminishes the direct impact of Co crystal structure, but improves the selectivity to C2+ hydrocarbons along with higher CO2 conversion. This seems to result from another pathway originating from HCOO* intermediate from bonding interaction of surface Co atoms with carbon in CO2, leading to the formation of CHx* whose coupling subsequently give rises to C2+ products. The present study sheds new light into the crystallographic structural sensitivity of CO2 hydrogenation towards the rational design of more selective catalysts for CO2 conversion.
查看更多>>摘要：Herein, we report a hydrogen peroxide-free resin photo-Fenton system with separation-free, low-cost, and strong mineralization ability of efficiently degrading organic pollutants (phenols, endocrine disruptors, antibiotics, and dyes). Based on the synergistic effect of hydroxyl radicals and holes, the corresponding degradation rate for Bisphenol A (BPA) was 11 times and 14.6 times higher than that of P-g-C3N4 and CdS/rGO photo-self-Fenton, respectively. The excellent performance is mainly attributed to a nearly 100% reduction of iron ions by electrons and promoted hydrogen peroxide utilization of 82.1%. Meanwhile, the introduction of strong oxidizing holes (2.15 eV) prevented the generation of macromolecular polymer intermediates, leading to a directly aromatic ring-opening and high mineralization efficiency (67%). This work exhibits a promising role of resin in visible-light photo-self-Fenton systems, offering a new route for eco-friendly and efficient wastewater treatment.
查看更多>>摘要：Despite the significant role of single atoms during the hydrogen evolution reaction (HER), the underlying nature of the synergetic effect between substrates and single atom is still unclear. Herein, through anchoring Pt single atoms on cobalt sulfide support (Pt@CoS), the roles of Pt single atoms and the substrate for alkaline HER catalysis are unfolded. Electrochemical studies demonstrate the remarkable catalytic performance of Pt @CoS catalysts with a 45-fold increase in mass current density compared to the benchmark Pt/C at 100 mV. The DFT calculation unravels that the anchored Pt SAs on CoS enable more unhybridized d(z)(2) orbitals of surrounding cobalt sites through the interfacial synergetic effect, which benefits the water dissociation kinetics. Likewise, the Pt sites can also act as active sites to facilitate the subsequent H-2 formation, thus synergistically promoting the alkaline HER catalysis. This work highlights the importance of the synergies effect between single atoms and substrate for rational catalyst design.
查看更多>>摘要：The increasingly massive consumption of plastics is becoming a global pollution disaster, with serious environmental and economic problems. Here we report an efficient and sustainable strategy for the visible-light driven upcycling of various plastic wastes into high-value-added formic acid. We firstly design and fabricate a self-assembly Z-scheme heterostructure of V-substituted phosphomolybdic acid clusters/g-C3N4 nanosheets (VPOM/CNNS). The Z-scheme charge transfer process is unambiguously elucidated by transient absorption spectra and electron spin resonance studies, which endow VPOM/CNNS heterostructure with efficient charge separation and strong redox potentials. Consequently, VPOM/CNNS heterostructure displays a superior photo catalytic performance toward upcycling of various plastics. The optimal VPOM/CNNS composite exhibits a remarkable formic acid production rate of 24.66 mu mol h(-1) g-1 for upcycling of polyethylene, which is 262-fold higher than that of pristine CNNS. This work highlights the potential of Z-scheme heterojunction as an unusual tool for the photo-driven upcycling of plastic waste.
Ramon, Adriana P.Li, XianshengClark, Adam H.Safonova, Olga V....
16页
查看更多>>摘要：Dry reforming of methane (DRM) is a promising process to generate synthetic gas with a low H-2/CO ratio. The main issues in DRM are the deposition of carbon over the catalyst and active metal sintering. Pyrochlores and perovskites are stable materials with properties that can overcome these challenges due to the presence of well dispersed active metal and oxygen vacancies. La2Ce2O7 and LaNiO3 mixed oxides containing 5 wt% of nickel were synthesized by modified Pechini and hydrothermal methods. The reduction of the La2Ce2O7 and LaNiO3 mixed materials was followed by in situ X-ray diffraction, ambient pressure X-ray photoelectron spectroscopy (APXPS), and X-ray absorption near edge structure. An oxygen-deficient perovskite La2Ni2O5 was identified already at room temperature. Both catalysts were stable during the performance test at low-(600 degrees C) and high-(850 degrees C) temperature DRM reaction, thanks to a negligible carbon accumulation on the catalyst surface. The high amount of electrophilic oxygen species, oxygen vacancies and basic sites detected correlates with the high catalytic activity. The material synthesized by hydrothermal method showed the highest conversion and yield. The better performance in this catalyst was related to higher amount of intermediate basic sites, oxygen vacancies and greater interaction between nickel and cerium. The reaction mechanism proposed in these materials takes into account the intermediates CHx and adsorbed O/OH, which were observed by means of APXPS.
查看更多>>摘要：Maintaining stable catalytic performance for chlorinated volatile organic compounds (CVOCs) oxidation in Pbcontaining scenarios is an intractable challenge for the industrial application of Ru-based catalysts. Herein, we systematically investigated the effect of Pb poisoning on the activity over various Ru-based catalysts during the CVOCs oxidation and explored the possible Pb resistance mechanism. The source of high Pb resistance was clarified from two aspects: (1) oxygen vacancies on supports (CeO(2 )or TiO2) captured Pb and firmly locked it in lattice, namely strong capture effect; and (2) the formation of stable Ru-O-M (M = Ce and/or W) bonds weakened the affinity between active Ru sites and Pb, ensuring the preferential deposition of Pb at oxygen vacancies. With the synergistic effect of above factors, the intrinsic activity (mainly strong acidity) of Ru sites in Ru/CeO2 and RuW/TiO(2 )catalysts was retained, which ensured the efficient dissociation of C-Cl bond and oxidation of CB.
查看更多>>摘要：Ground-level ozone causes great harm both to ecosystems and human health and should be strictly controlled. Manganese oxide (MnOx) is severely limited by catalyst deactivation due to environmental variations such as humidity and temperature. Herein, amorphous MnOx, prepared via a simple and mild redox reaction showed complete elimination of 40 ppm ozone at a high weight hourly space velocity of 600,000 mL.g(-1) h(-1), under the mild environmental condition with the relative humidity of 50 % and 25 ?C. It also kept predominant activity and remarkable stability even at harsh environmental conditions of low temperature (0 ?C) or high humidity (90 %). The superior ozone decomposition performance of MnOx resulted from the abundant grain boundaries and manganese redox pairs, which promoted oxygen vacancies generation and electron transfer. The findings may shed new light on the design of highly efficient and stable MnO(x )catalysts and are expected to drive great advances for large-scale practical applications.
查看更多>>摘要：Various MnOx phases and crystals were investigated in peroxymonosulfate (PMS) activation for oxidation of aqueous phenolic pollutants. MnOx with controlled crystal structure (alpha, beta, gamma, and amorphous-MnO2) and redox states (Mn2O3, and MnO) can induce different oxidative pathways toward organic polymerization against degradation in acidic conditions. Surface Mn-(s())II and Mn-(s)(III) of MnOx tend to bond with PMS to generate confined Mn-(s)((II, III))-(HO)OSO3- complexes to initiate a nonradical electron-transfer pathway (ETP). Meanwhile, high valence Mn/vs) in MnOx will directly attack micropollutants and spontaneously be reduced to low-valence states (Mn-(s)(II) and Mn-(s())III to initiate ETP. Mn2O3 can activate PMS to generate other radical species for mineralization. ETP will selectively initiate one-electron abstraction of phenol molecules into monomer phenoxy radicals and polyphenols on catalyst surface. Thus, manganese crystal structures will govern the surface redox species to induce multiple oxidation pathways toward different polymer products for water decontamination and carbon recycle.
查看更多>>摘要：Cobalt and oxides are the most recognized catalysts for peroxymonosulfate (PMS)-based advanced oxidation processes. However, the valence states - catalysis relations remain ambiguous. Herein, Co0/CoO/Co3O4 @K, N, O-doped carbons (Co-K-N-O-C) were synthesized via low-temperature pyrolysis. The cobalt species resulted in defective and doped carbons, and KOH facilitated the formation of low-valent Co species and carbon porosity. The synergy between Co and K facilitated peroxymonosulfate (PMS) activation and ciprofloxacin (CIP) mineralization due to enhanced electron transfer. Kinetics analysis was coupled with quenching experiments, electron paramagnetic resonance (EPR) detection and chemical probe identification to elucidate the contributions of each reactive oxygen species. As a result, hydroxyl radical (HO center dot) dominated the degradation (-64.8 +/- 1.2%), followed by sulfate radicals (SO4 center dot , -34.2 +/- 1.1%) and singlet oxygen (1O2, <2.0%). The low-valent Co species, especially Co0, greatly promoted radical generation. This study dedicates to in-depth elucidation of PMS activation mechanisms over metal/oxides@carbon composites for purifying recalcitrant contaminants in wastewater.
查看更多>>摘要：Solar-driven hydrogen evolution from urea-rich wastewater is a highly promising energy-environment bi-functional synthetical solution, while the intrinsic contradict between spectral energy quantity and quality of sunlight limits the existing wavelength-dependent technologies. Herein, we report the first demonstration of concentrated photo-thermo-catalysis (CPTC) technology that regulates the spectral energy quantity and quality and creates the synergy between photon and thermal effects to achieve full-spectrum solar harmonic conversion of aqueous urea and urine into hydrogen. The 50% enhanced CPTC performance compared with sole photo-/thermo-catalysis is achieved due to: (1) Catalyst structure optimization. Single Cu atom and 2D Cu raft are acquired on defect-rich TiO2 support by photo-thermo-organized metal-support interaction; (2) Reaction pathway expansion. The breakthrough against thermodynamic barrier of urea to hydrogen is realized by the novel cascade reactions of thermally-triggered urea hydrolysis and thermally-assisted ammonia photo-decomposition. The technological viability is convincingly presented through outdoor test with artificial urine under real sunlight.
NSTL
Elsevier