Direct epoxidation of propylene (DEP) by molecular oxygen is an ideal way to synthesize propylene oxide (PO), yet it remains quite challenging. We demonstrated here that the PO formation rate and selectivity could be enhanced simultaneously through photo-thermo-catalysis over the Cu/TiO2 catalyst. At 180 degrees C, by introducing light, the PO formation rate increased more than 20-fold (from 8.2 to 180.6 mu mol center dot g(-1)center dot h(-1)) and the corresponding selectivity improved more than 3-fold (from 8% to 27%), breaking the traditional perception that the semiconductors exhibit very low reactivity for this reaction. Kinetic study results showed that the apparent activation energy for PO formation could sharply decrease under light irradiation (from 95 to 40 kJ center dot mol(-1)). In situ electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were applied to characterize the dynamics of the valence state of the copper oxide species and the activation intermediates of molecular oxygen. Evidence for the activation of oxygen, which could direct to the PO formation pathway, was captured. The light-driven electrons could promote the formation of active Cu+, which could form the side-on mu-peroxo Cu(II)(2) structure, weaken the O - O bond, and improve the PO formation rate and selectivity. This work paves a new way for designing semiconductor-supported photocatalysts for DEP reactions with molecular oxygen.

Controlling the precise placement of active metals on supports is highly desirable yet challenging, which governs both the reaction pathway and the ultimate outcomes of catalytic reactions. Herein, the Cu species are positioned to the Lewis acidic sites created by the ultrahigh-temperature calcination of TiO2, where the atomic structures of the Lewis acids are identified as five-coordinated Ti4+ cations bound to three-coordinated O2- anions (L-beta sites) by in situ characterizations. Owing to the robust chemical affinity, CuOx manifests itself as a nanopatch. The Cu/TiO2 catalyst without any modifications exhibits a propylene oxide (PO) formation rate of 44 mmol g(Cu)(-1) h(-1) for direct epoxidation of propylene using molecular oxygen (DEP). The PO yield on Cu/TiO2 can be efficiently correlated with the quantity of the decreased Lewis acids, which demonstrates that the intimated interaction between the Cu species and Lewis acids should be responsible for PO production. Furthermore, density functional theory calculations suggest that Cu+ in the Ti-O-Cu interface formed at the L-beta sites is the active site of the DEP reaction, with the aid of the adjacent Cu atom. This study provides a Cu-based catalyst for the DEP reaction.

Catalytic oxidation is a commonly employed technology in the industry for removing volatile organic compounds (VOCs) due to its exceptional efficiency under mild operating conditions. Although supported Pt-based nano-catalysts are recognized widely as one of the most promising and extensively used industrial catalysts for VOC abatement, their practical application, and development are restricted by their exorbitant cost. Single-atom catalyst (SAC) with maximized metal utilization and exclusive electronic character has been explored extensively in various catalytic reactions. However, Pt SAC is usually deemed to be inactive in hydrocarbon oxidation reactions in thermal catalysis, compared with its nanoparticle counterpart. Here, we demonstrate that the WO3-TiO2 supported Pt SAC (Pt1/WO3- TiO2) exhibits much higher activities than the corresponding nanoparticle catalyst (PtNP/WO3-TiO2) in photo-thermo catalytic oxidation of C3H8 and C3H6, which represent different kinds of typical VOCs. A key finding is that the activities of Pt1/WO3- TiO2 and PtNP/WO3-TiO2 can be accelerated in photo-thermo catalytic C3H8 oxidation by overcoming oxygen poisoning. Upon the light irradiation, the apparent active energy (Ea) of the Pt1/WO3-TiO2 and PtNP/WO3-TiO2 decline from 116 to 60 kJ.mol-1 and from 103 to 30 kJ.mol-1, respectively, substantiating their effectiveness in photo-thermo catalysis. Notably, a substantially higher reaction rate of 3792 & mu;mol & BULL;gPt-1 & BULL;s-1 on the Pt1/WO3-TiO2 is achieved, which should be a benchmark for C3H8 oxidation. More intriguingly, photo-thermo catalytic C3H6 oxidation on the PtNP/WO3-TiO2 is prohibited due to the strong adsorption-induced C3H6 poisoning on the Pt nanoparticles, for which the Ea of the PtNP/WO3-TiO2 catalyst for C3H6 oxidation is maintained at approximately 55 kJ.mol-1, regardless of the light irradiation. In comparison, the C3H6 poisoning on the Pt1/WO3-TiO2 can be mitigated by light illumination, where the Ea of the Pt1/WO3-TiO2 catalyst for C3H6 oxidation dramatically reduced from 49 to 16 kJ.mol-1, signifying that the high energy barrier of C3H6 oxidation can be mediated by the light. Profiting from the apt affinity between C3H6 and Pt single atoms, the photogenerated electrons accumulated on the Pt single atoms produce repulsive force towards the electron-rich C3H6 molecules, which is conducive to the C3H6 desorption from the Pt1/WO3-TiO2. Therefore, the Pt1/WO3-TiO2 exhibits enhanced activity in photo-thermo catalytic C3H6 oxidation. This study exemplifies that the advantages of SAC are not only saving the consumption of precious metals but also discovering new catalytic reactions on the account of the specific electronic characteristic.

Propane dehydrogenation (PDH) is a crucial and effective technology to produce propylene industrially and is in great demand around the globe. Silica/zeolite-supported PtZn bimetallic catalysts have been reported to exhibit long-term operation and a consecutive regeneration process at high temperatures. However, over the industrially most commonly used support Al2O3, PtZn bimetallic nanoparticles suffer from low stability. Herein, we develop Zn-doped Al2O3 (ZnAlO x ) to stabilize PtZn nanoparticles (<1 nm) for the PDH reaction, for which the structure and composition of the PtZn intermetallic nanoparticles could be controlled by tuning the ratio of Zn/Al. The optimized catalyst with Zn/Al = 1/5 (mole ratio) exhibited the most remarkable stability with an extremely low k d value of 0.0007 h-1 and survived 10 cycles of regeneration tests with negligible deactivation. Characterizations by HAADF-STEM, XAS, and XRD, together with in situ XPS and CO-DRIFTS, proved that the excellent performance originated from the Pt1Zn1 intermetallic compound formed during the reaction and the enhanced interaction between the Pt1Zn1 nanoparticles and the Zn-doped Al2O3 support.

采用共浸渍法制备PtZn/β-x(x为SiO2/Al2O3物质的量比)分子筛双金属催化剂,探究了β分子筛中硅铝比对丙烷非临氢脱氢反应性能的影响.采用XRD、BET、HAADF-STEM、NH3-TPD、C3H6-TPD等一系列表征技术对催化剂的物相结构、表面性质及其对丙烷非临氢脱氢反应性能的影响进行了研究.结果表明,催化稳定性随载体中Si/Al比的增大而提高(稳定性顺序:PtZn/DeAl-β＞PtZn/β-40＞PtZn/β-30＞PtZn/β-25),而催化剂的强酸位点数量(PtZn/β-30＞PtZn/β-40＞PtZn/β-25＞PtZn/DeAl-β),在一定程度上受硅铝比的影响,与丙烯选择性顺序相反.因此,分子筛的Si/Al比对催化剂的性质有重要的调变作用,当催化剂强酸位点较少、丙烯吸附较弱、比表面积较大时,有助于提高丙烷转化率、丙烯选择性和催化稳定性.

The direct CH4 conversion (DMC) to methanol is a challenging topic. In this study, the Ru/SZ (sulfated zirconia) single-atom catalysts (SACs) were synthesized and utilized to the DMC to methanol under mild conditions (70 °C). The yield over the Ru/SZ SACs (18.32 µmol, TOF ≥ 80 h–1) significantly exceeded the sum of the yields over the SZ (0.67 µmol) and Ru/ZrO2 (0.29 µmol), indicating that a new active center was formed on the Ru/SZ SACs. Combined with the results of the 13CH4 isotope labeling experiments and various characterizations including the pyridine adsorption infrared spectroscopy, electron paramagnetic resonance and X-ray photoelectron spectroscopy, an unprecedented synergy effect between the single-atom and the super acid sites was pictured: The strong acidity of the Ru/SZ SACs could effectively promote the decomposition of H2O2 into the •OH, and the Ruδ+ (δ > 4) and the adjacent Zrγ+-•OH (γ > 4) could synergistically catalyze the CH4 to methanol.

The PtSn/Al2O3 is a prototypical industrial catalyst for propane dehydrogenation (PDH). However, the local structures of the active sites are still inconclusive under the operation conditions. Herein, the evolutions of the Pt-Sn active centers supported on nano-Al2O3 are definitely discerned at the atomic level during PDH reaction. By combining complementary in situ characterizations and theoretical calculations, we demonstrate that a highly productive Sn1Pt single-atom alloy (47.6 molC3H6 gPt–1 h–1) forms after the reduction, and thereby self-assembles to the Pt3Sn intermetallic compound during the reaction, which exhibits a rather stable performance (kd-10~40h: 0.0026 h–1). Intriguingly, the results of in situ diffuse reflectance infrared Fourier-transform spectroscopy further corroborate that the adjacent Pt atoms with terrace sites aggravating the coke deposition can be circumvented through this single-atom alloy mediated reconstruction. Our findings depict an unprecedented evolution process of the active sites of the PtSn/Al2O3, and afford an effectual nanostructure engineering pathway for stable PDH catalysts.

The photocatalysis of direct dehydrogenation of benzyl alcohol to benzaldehyde is an energy saving way to synthesize fine chemicals and pure hydrogen by using solar energy. The CdS-based catalysts were one of the typical kinds of photocatalysts for this reaction. The morphology of CdS could be easily tuned, which could greatly influence the photocatalytic performances. However, the morphology effect of CdS on the photocatalytic behaviour of the direct dehydrogenation of benzyl alcohol has not been investigated yet. In this work, we synthesized CdS with two different morphologies (nanosheet (NS) and nanowire (NW)) and found the CdS-NS showed much higher photocatalytic activity for converting the benzyl alcohol than the CdS-NW, but the selectivity to benzaldehyde over the two supports was very low. By depositing Au25 nanoclusters on the CdS-NW and CdS-NS, the morphology effect of the CdS support could be mitigated and their catalytic activity and selectivity could be greatly boosted for the photocatalytic anaerobic dehydrogenation of benzyl alcohol to benzaldehyde and H2. The results of this work would provide new insight into the design of efficient photocatalysts for synthesizing fine chemicals.

Pt-based catalysts are the typical industrial catalysts for propane dehydrogenation (PDH), which still suf-fer from insufficient long-term durability due to the structural instability and coke deposition. A commer-cial c-Al2O3 supported thermally robust sub-nanometer Pt2In3 intermetallic catalyst with atomically ordered structure and rigorously separated Pt single atoms was fabricated, which showed outstanding robustness in 240 h long-term operation at 600 & DEG;C with the deactivation rate constant kd as low as 0.00078 h-1, ranking among the lowest reported values. Based on various in situ characterizations and theoretical calculations, it was proved that the catalyst stability not only resulted from the separated Pt single-atom sites but also significantly affected by the distance of adjacent Pt atoms. An increasing dis-tance to 3.25 & ANGS; in the Pt2In3 could induce a weak p-adsorption configuration of propylene on Pt sites, which facilitated the desorption of propylene and restrained the side reactions like coking.CO 2023 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.

Synthesis of methyl methacrylate (MMA) via direct oxidative esterification from methacrolein (MAL) and methanol (MeOH) is of great significance in chemical industry. Supported gold catalysts are considered as one of the most potential candidates for this reaction but suffer from low activity and deactivation issue. Herein, by modulating the phase structure of hydroxyapatite (HAP) with different cations and anions, a synergic effect between gold and vanadate substituted hydroxyapatite (HVP) support for the synthesis of MMA was discovered. In direct oxidative esterification, among the evaluated catalyst/support systems, Au/HVP catalyst displays the best performance and unprecedented stability, which acts as one of the best-performing gold catalysts for oxidative esterification. Various characterizations such as X-ray diffraction (XRD), Raman spectra, scanning electron microscopy (SEM), transmission electron microscope (TEM) and in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) of CO were conducted to disclose the structural and electronic property of the catalysts. Through in-situ FT-IR spectra of MAL and MeOH, the substrate was proved to be easily transformed on Au/HVP catalyst to ester. Besides, the presence of O2 was found to facilitate the adsorption of MAL. The results of temperature programmed desorption (TPD) of O2 implied that gold particles together with HVP support is promotional for activation and dissociation of oxygen, leading to good activity and high selectivity.

Restricting the Pd sintering during aging is crucial for the three-way catalysts (TWCs). Herein, following the Ostwald-ripening mechanism, Pd sintering in the commercial TWCs was greatly suppressed by increasing the initial size of the Pd NPs, through a pre-precipitation method. Our catalysts showed initially larger Pd NPs after calcination at 550 degrees C (3.3 vs. 1.8 nm) while smaller ones after aging at 1000 degrees C (35.0 vs. 70.1 nm) than the counterpart made by impregnation. The optimal aged catalyst showed much better performance than the counterpart: T50 was decreased by 40, 13 and 14 degrees C for CO, NO and C3H6 over the powder samples, and a higher oxygen storage capacity was observed (248 > 178 mg/L) over the monolith converters. The decreased size of the Pd NPs and the improved reducibility as well as the more concentrated adsorbed oxygen species for the optimal aged catalyst were responsible for the improved performance.

Electrocatalysts for efficient production of ammonia from nitrogen reduction reaction (NRR) under ambient conditions are attracted growing interest in recent years, which demonstrate a great potential to replace the Haber-Bosch method which suffers the problems of the huge energy consumption and massive CO2 production. In this work, a novel electrocatalyst of Au25 -Cys-M is fabricated for NRR under ambient conditions, with transition metal ions (e.g., Mo6+ , Fe3+ , Co2+ , Ni2+ ) atomically decorated on Au25 nanoclusters via thiol bridging. The Au25 -Cys-Mo catalyst exhibits the highest Faradaic efficiency (26.5%) and NH3 yield (34.5 µg h-1  mgcat -1 ) in 0.1 m HCl solution. X-ray photoelectron spectroscopy analysis and high angle annular dark field image-scanning transmission electron microscopy characterization reveal that the electronic structure of Mo is optimized by forming the structure of Au-S-Mo and Mo acts as active sites for activating the nitrogen to promote the electrochemical production of ammonia. This work provides a new insight into the precise fabrication of efficient NRR electrocatalysts.

It remains a challenge to make metal oxides with limited reducibility as active component rather than support or modifier for the oxidative dehydrogenation (ODH) of light alkanes. Here, we report a special TiO 2 (M-TiO 2 ) evolved from Ti 3 C 2 T x MXene material to be a new kind of efficient catalyst in the ODH of ethane. The reactivity on this M-TiO 2 is four times higher than that on P25 TiO 2 , endowing an excellent ethylene productivity of 15.4 g C2H4 g cat -1 h -1 that outperforms the previously reported catalysts. Experimental characterizations and theoretical calculations reveal the existence of both Ti and oxygen vacancy defects on M-TiO 2 . The Ti defect can increase the reducibility of M-TiO 2 to reduce the activation barrier of ethane while the oxygen vacancy facilitates the adsorption of O 2 to recover lattice oxygen, accounting for the high performance. This work enlightens the defect engineering of traditional metal oxide as a promising catalyst in the oxidation catalysis.

Cost-efficient and durable oxygen evolution catalysts are in great demand, which are dominated not only by the component of the electrocatalysts but also by their molecular structure and crystallinity. Herein, we developed an efficient cobalt-vanadium spinel-type electrocatalyst with an extremely high concentration of Co3+ ions by tuning the balanced vanadium ions' concentration in crystallinity-modulated Co2-xVxO4 nanoplates. This resulted in the lowest overpotential of 240 mV at 10 mA/cm(2), the smallest Tafel slope of 45 mV dec(-1), and a current density of 100 mA/cm(2) at an overpotential of 280 mV for water oxidation, which is remarkably 20 times better than that of the benchmark RuO2 catalyst, along with excellent stability. Such excellent performance is due to the very high Co3+/Co2+ ratio of 2.84 achieved in situ in the lowcrystallinity Co2-xVxO4 (LC-Co2-xVxO4) sample, which is 40% higher than that of the widely reported Co3O4, as evidenced by both operando X-ray absorption near-edge spectroscopy and in situ X-ray photoelectron spectroscopy. These findings stimulate the opportunities to explore Co2-xVxO4 as a class of nonprecious-metal-based efficient OER electrocatalysts.

Oxygen carriers with active sites have attained wide attention for chemical looping reforming of CH4 recently thanks to their capacity to improve CH4 activation and oxygen reactivity. However, supported metals sintered significantly during multiple cycles, which entailed high metal loading (generally >5 wt %) to realize great performance promotion and caused coke formation. Herein, merely 0.1 wt % Ni addition into CeO2 could achieve remarkable enhancement of performance for chemical looping drying reforming of methane with CH4 conversion and CO selectivity of almost 100% as well as syngas productivity of 3.4 mmol/g without carbon deposition. This resulted from the encapsulation of Ni nanoparticles by CeO2 via the strong metal-support interaction during redox cycles preventing Ni nanoparticles from sintering, which brought about more surface oxygen vacancy for CH4 activation compared with CeO2. Nonetheless, the covering could not be observed in 5Ni/CeO2 resulting in the evident growth of Ni nanoparticles, which induced CH4 cracking on them and thus coke formation.

The high transmittance, environmentally robust, and unique interaction with water make lanthanide series rare-earth oxides promising for various applications such as next-generation self-cleaning coatings. However, the underlying mechanism of the anomalous hydrophobicity in lanthanide oxides remains controversial due to the lack of molecular-level studies in a well-controlled environment, which greatly limits the possibility to engineer their wettability for broader technical applications. Here, we systematically studied the mechanism that governs the wetting behaviors of ceria films by in-situ X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and water contact angle measurements under the environmentally controlled conditions. It was found that the hydrophobicity of ceria was mainly contributed by the adsorbed hydrocarbon, and the wettability could be enhanced on cleaner ceria surfaces with more degree of hydroxylation. Based on the significant dependence of wetting property on surface contamination, we further developed an in-situ annealing method to significantly improve the water-splitting performance of ceria powders by removing hydrocarbon contamination. These results suggest that the removal of surface contamination by high-grade oxidation is the key factor to facilitate the water dissociation of ceria films, providing new insights into the control of their wetting property and design of high-performance devices based on ceria films.

Long-term stable perovskite solar cells (PSCs) fabricated in ambient conditions are highly desirable. However, the stable perovskite film has yet to be easily controlled in open air, especially employing ZnO as an electron transportation layer. Here, the roles of cetyltrimethylammonium bromide (CTABr) were further investigated on ZnO-based PSCs, including more details of the grain boundaries and the interaction mechanism between CTABr and perovskite layer. The average efficiency of the unsealed CTABr-modified PSCs could remain at 93.2% of their original level after exposing to the environment with 60-65% relative humidity for as long as 2150 h. Meanwhile, the efficiency of the PSCs with the structure of fluorine-doped tin oxide (FTO)/ZnO/MAPbI(3)-CTABr/Spiro-OMeTAD/Au was also increased obviously. To deepen the understanding of the roles of CTABr, various powerful techniques such as synchrotron-based grazing incidence X-ray diffraction, Hall effect measurement, space-charge-limited current, and density functional theory calculations were used. Our work would deepen the understanding of the enhancement mechanism of CTABr on PSCs.

The IB metal (Au, Ag and Cu) alloyed Pd single atom catalysts had been proved to be efficient in promoting the selectivity for hydrogenation of acetylene to ethylene. As a base metal in the same group as Pd, the Ni-based catalysts are also active for hydrogenation reactions. Herein, the effects of the IB metals on the Ni/SiO2 catalyst for the selective hydrogenation of acetylene were systematically studied. Different from the Pd/SiO2 catalyst, the monometallic Ni/SiO2 catalyst is not active at low temperatures. The addition of the IB metals to the Ni/SiO2 catalysts can greatly enhance the activity. Besides, the catalytic activity of the AuNix/SiO2 and CuNix/SiO2 catalysts increase with the reduction temperature, while the AgNix/SiO2 catalysts are not sensitive to the pretreatment temperature. The origin of the effect of the different IB metals on the Ni-based catalysts for selective hydrogenation of acetylene is discussed based on the characterizations by XRD, TPR and microcalorimetric measurements.

AbstractPhoto–thermo catalysis, which integrates photocatalysis on semiconductors with thermocatalysis on supported nonplasmonic metals, has emerged as an attractive approach to improve catalytic performance. However, an understanding of the mechanisms in operation is missing from both the thermo‐ and photocatalytic perspectives. Deep insights into photo–thermo catalysis are achieved via the catalytic oxidation of propane (C3H8) over a Pt/TiO2‐WO3 catalyst that severely suffers from oxygen poisoning at high O2/C3H8 ratios. After introducing UV/Vis light, the reaction temperature required to achieve 70 % conversion of C3H8 lowers to a record‐breaking 90 °C from 324 °C and the apparent activation energy drops from 130 kJ mol−1 to 11 kJ mol−1. Furthermore, the reaction order of O2 is −1.4 in dark but reverses to 0.1 under light, thereby suppressing oxygen poisoning of the Pt catalyst. An underlying mechanism is proposed based on direct evidence of the in‐situ‐captured reaction intermediates.