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Chinese Journal of Catalysis
2020, Vol. 41, No. 8
Online: 18 August 2020

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Cover: Zhao and Ali in their Article on pages 1174–1185 reported the method for synthesis of hydrophillic mesoporous Ru/carbon, which is rich in –OH groups. This catalyst delivered the tandem hydrogenation and decarbonylation steps for production of quantitative yields of diesel-range alkanes from microalgae oil at a low temperature of 140 ℃ in aqueous phase.

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Table of Contents for VOL.41 No.8 2020, 41 (8):  0-0.  Abstract ( 18 )   PDF (1627KB) ( 13 )

Communications

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Engineering Ru(IV) charge density in Ru@RuO2 core-shell electrocatalyst via tensile strain for efficient oxygen evolution in acidic media Yizhi Wen, Tao Yang, Chuanqi Cheng, Xueru Zhao, Enzuo Liu, Jing Yang 2020, 41 (8):  1161-1167.  DOI: 10.1016/S1872-2067(20)63543-4 Abstract ( 128 )   [Full Text(HTML)] () PDF (1502KB) ( 290 )   Supporting Information The design of efficient Ru-based electrocatalysts with high intrinsic activities for acidic water oxidation is highly desirable and challenging for water splitting in proton exchange membrane electrolyzers. Here, for the first time, we engineer the charge density of Ru(IV) by creating tensile strains in the RuO2 shell of Ru@RuO2 core-shell nanoparticles, viz. Ru@RuO2-L. High-resolution spectroscopic characterizations confirm the presence of av. 6% tensile strain in Ru-O bonds, which results in an effective reduction of the Ru(IV) charge density. The resultant RuX+ (4 < X < 5) active sites greatly accelerate the oxygen evolution reaction (OER) in an acidic electrolyte, leading to a remarkably low overpotential of 191 mV at 10 mA cm-2. These values are lower than those for the benchmark RuO2 catalyst and are also among the lowest for efficient Ru-based electrocatalysts reported thus far. The specific activity and mass activity are also greatly enhanced 4.2-fold and 17.7-fold compared to those of RuO2, respectively. The acidic OER activity improvement is ascribed to the lowered adsorption energy of *OOH, owing to the reduced charge density of Ru(IV), and the rapid charge transport owing to the Ru core. Ru@RuO2-L also demonstrates high feasibility as the anode catalyst for the overall water splitting in acidic media.

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C(sp2)-H/O-H cross-dehydrogenative coupling of quinoxalin-2(1H)-ones with alcohols under visible-light photoredox catalysis Long-Yong Xie, Yi-Shu Liu, Hong-Ru Ding, Shao-Feng Gong, Jia-Xi Tan, Jun-Yi He, Zhong Cao, Wei-Min He 2020, 41 (8):  1168-1173.  DOI: 10.1016/S1872-2067(19)63526-6 Abstract ( 57 )   [Full Text(HTML)] () PDF (835KB) ( 172 )   Supporting Information An efficient and practical route to various 3-alkoxylquinoxalin-2(1H)-ones through visible-light photocatalytic C(sp2)-H/O-H cross-dehydrogenation coupling of quinoxalin-2(1H)-ones and alcohols, employing ambient air as an oxidant at room temperature under metal-free conditions, was developed.

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Ru nanoparticles supported on hydrophilic mesoporous carbon catalyzed low-temperature hydrodeoxygenation of microalgae oil to alkanes at aqueous-phase Arif Ali, Chen Zhao 2020, 41 (8):  1174-1185.  DOI: 10.1016/S1872-2067(20)63539-2 Abstract ( 77 )   [Full Text(HTML)] () PDF (1751KB) ( 184 )   Supporting Information The processing of an energy carrier such as microalgae oil into valuable fuels and chemicals is quite promising. Aqueous-phase processing is suitable for this purpose because the separation of intrinsic water from the algae cell is difficult. In this study, we synthesized ruthenium (Ru) nanoparticles supported on highly hydrophilic mesoporous carbon to catalyze the quantitative hydrodeoxygenation (HDO) of microalgae oil to alkanes in a one-pot process at a low temperature (140℃) in the aqueous phase. The mesoporous carbon was obtained by single-step calcination of starch and zinc chloride in nitrogen. The as-obtained carbon showed high surface areas and pore volumes, allowing high dispersion of Ru nanoparticles. The surface of the carbon material was rich in hydroxyl groups, as evidenced by X-ray photoelectron spectroscopy (XPS), infrared (IR) spectroscopy, and thermogravimetric analysis (TGA) measurements. As a result, the carbon material contacted preferably with the water phase versus the organic phase, improving the accessibility of substrates. On the other hand, the contact angle test results speculated the superior hydrophilic nature of mesoporous Ru/C (ZnCl2, starch) than commercial Ru/C. Both kinetics modeling and in situ IR monitoring in water revealed the superior performance of the hydrophilic mesoporous and hydrophilic Ru/C compared to a commercial Ru/C for the tandem hydrogenation of stearic acid and decarbonylation of stearyl alcohol. The herein designed hydrothermal carbon material was highly active, environmentally benign, sustainable, and recyclable material, and could be potentially used for other hydrogenation reactions in the aqueous phase.

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Robust photocatalytic benzene degradation using mesoporous disk-like N-TiO2 derived from MIL-125(Ti) Chen Zhao, Zhihua Wang, Xi Chen, Hongyu Chu, Huifen Fu, Chong-Chen Wang 2020, 41 (8):  1186-1197.  DOI: 10.1016/S1872-2067(19)63516-3 Abstract ( 129 )   [Full Text(HTML)] () PDF (1152KB) ( 219 )   Supporting Information N-doped anatase-rutile titanium dioxide (N-TiO2) is a classical semiconductor widely used in environmental remediation. Its photocatalytic performance is typically affected by its morphology, porous structure, and phase composition. Herein, disk-like mesoporous N-TiO2 was prepared by calcining MIL-125(Ti) and melamine matrix at different temperatures in air. The photocatalytic efficiency of the prepared mesoporous N-TiO2 for the photo-oxidation of gaseous benzene under visible-light irradiation was studied. With respect to light absorption and mass transfer, as-prepared N-TiO2 annealed at 500℃ (MM-500) showed the best photocatalytic activity with corresponding photodegradation and mineralization efficiencies of 99.1% and 72.0%, respectively. In addition, MM-500 exhibited excellent reusability and stability in cyclic experiments, in which 84.8% of gaseous benzene could still be photodegraded after 10 experimental cycles. Furthermore, electron spin resonance analysis indicated that ·OH and ·O2- radicals were the dominating reactive oxygen species during the photo-oxidation process. Their excellent performance suggests that the as-prepared N-TiO2 photocatalysts can be used to eliminate volatile organic compounds.

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A facile sulfur-assisted method to synthesize porous alveolate Fe/g-C3N4 catalysts with ultra-small cluster and atomically dispersed Fe sites Sufeng An, Guanghui Zhang, Jiaqiang Liu, Keyan Li, Gang Wan, Yan Liang, Donghui Ji, Jeffrey T. Miller, Chunshan Song, Wei Liu, Zhongmin Liu, Xinwen Guo 2020, 41 (8):  1198-1207.  DOI: 10.1016/S1872-2067(20)63529-X Abstract ( 85 )   [Full Text(HTML)] () PDF (806KB) ( 317 )   Supporting Information Heterogeneous catalysts with ultra-small clusters and atomically dispersed (USCAD) active sites have gained increasing attention in recent years. However, developing USCAD catalysts with high-density metal sites anchored in porous nanomaterials is still challenging. Here, through the template-free S-assisted pyrolysis of low-cost Fe-salts with melamine (MA), porous alveolate Fe/g-C3N4 catalysts with high-density (Fe loading up to 17.7 wt%) and increased USCAD Fe sites were synthesized. The presence of a certain amount of S species in the Fe-salts/MA system plays an important role in the formation of USCAD S-Fe-salt/CN catalysts; the S species act as a "sacrificial carrier" to increase the dispersion of Fe species through Fe-S coordination and generate porous alveolate structure by escaping in the form of SO2 during pyrolysis. The S-Fe-salt/CN catalysts exhibit greatly promoted activity and reusability for degrading various organic pollutants in advanced oxidation processes compared to the corresponding Fe-salt/CN catalysts, due to the promoted accessibility of USCAD Fe sites by the porous alveolate structure. This S-assisted method exhibits good feasibility in a large variety of S species (thiourea, S powder, and NH4SCN) and Fe salts, providing a new avenue for the low-cost and large-scale synthesis of high-density USCAD metal/g-C3N4 catalysts.

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One-step fabrication of TiO2/graphene hybrid mesoporous film with enhanced photocatalytic activity and photovoltaic performance Junxiong Guo, Yiyi Li, Shangdong Li, Xumei Cui, Yu Liu, Wen Huang, Linna Mao, Xiongbang Wei, Xiaosheng Zhang 2020, 41 (8):  1208-1216.  DOI: 10.1016/S1872-2067(19)63511-4 Abstract ( 64 )   [Full Text(HTML)] () PDF (986KB) ( 148 )   Supporting Information We synthesized a mesoporous film based on TiO2-reduced graphene oxide (RGO) hybrids using a one-step vapor-thermal method without the need for an additional annealing process. The vapor-thermally prepared TiO2-graphene hybrid (VTH) features unique structures with an ultra-large specific surface area of ~260 m2 g-1 and low aggregation, giving rise to enhanced light harvesting and increased charge generation and separation efficiency. It was observed that a mesoporous film with uniform pore distribution is simultaneously obtained during the VTH growth process. When a 5.0 wt% RGO VTH film was used as the active layer in photocatalysis, the highest photocatalytic activity for degradation of methyl orange was achieved. For another, when a 0.75 wt% RGO VTH film was used as the photoanode in a dye-sensitized solar cell, the power conversion efficiency reached 7.58%, which represents an increase of 73.1% compared to a solar cell using an a photoanode of pure TiO2 synthesized by a traditional solvothermal method. It is expected that this facile method for the synthesis of TiO2/graphene hybrid mesoporous films will be useful in practical applications for preparing other metal oxide/graphene hybrids with ultra-high photocatalytic activity and photovoltaic performance.

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Versatile bifunctional nitrogen-doped porous carbon derived from biomass in catalytic reduction of 4-nitrophenol and oxidation of styrene Jiangyong Liu, Jinxing Li, Rongfei Ye, Xiaodong Yan, Lixia Wang, Panming Jian 2020, 41 (8):  1217-1229.  DOI: 10.1016/S1872-2067(20)63534-3 Abstract ( 85 )   [Full Text(HTML)] () PDF (1517KB) ( 199 )   Supporting Information The scarcity and weak durability of metal, especially precious metal catalysts are big obstacles for their large-scale application in many reactions. The state-of-the-art of the catalytic science prefers such type of catalysts, which can replace metal-based catalysts to alleviate energy and environmental crises and exhibit catalytic performance comparable to or even exceeding these metal catalysts. Herein, we report that N-doped porous carbon (NKC) derived from cheap and abundant radish can be employed as versatile and efficient bifunctional catalysts in both the catalytic reduction of 4-nitrophenol (NRR) and oxidation of styrene (SOR). The series of NKC catalysts were prepared with a simple and facile one-pot strategy by coupling the N-doping, carbonization and KOH activation processes. These catalysts show hierarchical porosity, with the specific surface area, total pore volume and N-doping content ranging from 918.9-3062.7 m2 g-1, 1.01-2.04 cm3 g-1 and 1.29-15.3 at%, respectively. Interestingly, our finding suggests that the catalytic performance is not directly related to these parameters but correlates positively with the content of graphitic N dopants, which is the dominant contributor for impelling both the NRR and SOR. Another intriguing finding is that for both reactions, the optimal catalyst was found to be the NKC-3-800 which possesses the highest graphitic N content of 3.13 at%. In addition, to gain insight into the catalytic behavior, analyses of kinetics and thermodynamics were performed, and the catalytic mechanisms were postulated. This work paves the way for the construction of biomass-derived N-doped carbon catalysts for bi-or even multi-functional applications in various organic reactions.

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Construction of nitrogen and phosphorus co-doped graphene quantum dots/Bi5O7I composites for accelerated charge separation and enhanced photocatalytic degradation performance Kai Li, Mengxia Ji, Rong Chen, Qi Jiang, Jiexiang Xia, Huaming Li 2020, 41 (8):  1230-1239.  DOI: 10.1016/S1872-2067(20)63531-8 Abstract ( 56 )   [Full Text(HTML)] () PDF (1494KB) ( 144 )   Supporting Information Nitrogen and phosphorus co-doped graphene quantum dot-modified Bi5O7I (NPG/Bi5O7I) nanorods were fabricated via a simple solvothermal method. The morphology, structure, and optical properties of the as-prepared samples were investigated by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), and diffused reflectance spectroscopy. The photocatalytic performance was estimated by degrading the broad-spectrum antibiotics tetracycline and enrofloxacin under visible light irradiation. The photodegradation activity of Bi5O7I improved after its surface was modified with NPGs, which was attributed to an increase in the photogenerated charge transport rate and a decrease in the electron-hole pair recombination efficiency. From the electron spin resonance spectra, XPS valence band data, and free radical trapping experiment results, the main active substances involved in the photocatalytic degradation process were determined to be photogenerated holes and superoxide radicals. A possible photocatalytic degradation mechanism for NPG/Bi5O7I nanorods was proposed.

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Site-specific deposition creates electron-rich Pd atoms for unprecedented C-H activation in aerobic alcohol oxidation Yang Yan, Bin Ye, Mingshu Chen, Linfang Lu, Jian Yu, Yuheng Zhou, Yong Wang, Juanjuan Liu, Liping Xiao, Shihui Zou, Jie Fan 2020, 41 (8):  1240-1247.  DOI: 10.1016/S1872-2067(20)63535-5 Abstract ( 41 )   [Full Text(HTML)] () PDF (1281KB) ( 132 )   Supporting Information Here, we demonstrate a photochemical strategy to site-specifically deposit Pd atoms on Au nanoparticles. The high-sensitivity low-energy ion scattering spectra combined with the X-ray photoelectron spectra reveal that the surface electronic structure of Pd can be continuously regulated by tailoring the Pd-to-Au molar ratio and the location of Pd atoms in AuPd nanoparticles. It is revealed that electron-rich Pd atoms are considerably more active than the net Pd atoms in aerobic alcohol oxidation. Remarkably, the catalyst with the most electron-rich Pd sites (binding energy downshift:1.0 eV) exhibits an extremely high turnover frequency (~500000 h-1 vs 12000 h-1 for that with net Pd atoms) for solvent-free selective oxidation of benzyl alcohol, which is, to the best of our knowledge, the highest value ever reported. Kinetic studies reveal that electron-rich Pd atoms can accelerate the oxidation of benzyl alcohol by facilitating C-H cleavage, as indicated by the significant reduction in the activation energy as compared to net Pd atoms.

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Dehydration of sugars to 5-hydroxymethylfurfural and non-stoichiometric formic and levulinic acids over mesoporous Ta and Ta-W oxide solid acid catalysts Bin Guo, Lulu He, Gangfeng Tang, Li Zhang, Lin Ye, Bin Yue, Shik Chi Edman Tsang, Heyong He 2020, 41 (8):  1248-1260.  DOI: 10.1016/S1872-2067(19)63519-9 Abstract ( 77 )   [Full Text(HTML)] () PDF (838KB) ( 183 )   A series of mesoporous Ta and Ta-W oxides have been prepared and employed as solid acid catalysts for the dehydration of fructose and glucose to 5-hydroxymethylfurfural (HMF). Solid state 31P MAS NMR spectroscopic results using trimethylphosphine (TMP) as a probe molecule show that the acid strength and the ratio of Brönsted to Lewis acid sites increase gradually with the addition of tungsten in tantalum oxide. It is found that high sugar conversion and HMF selectivity are achieved over catalyst with relatively high ratios of Brönsted to Lewis acid sites. Unexpected stoichiometric excess of formic acid relative to levulinic acid can be observed mainly because of direct decomposition of fructose over Lewis acid sites. The addition of 2-butanol leads to the increase of sugars conversion and the HMF selectivity, especially for the catalyst with high ratio of Brönsted to Lewis acid sites. Among them, Ta7W3 oxide catalyst shows 54% HMF selectivity and good reusability with the addition of 2-butanol by extracting HMF from aqueous phase and removing humins deposed on the surface of the catalyst.

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Understanding the deactivation behavior of Pt/WO3/Al2O3 catalyst in the glycerol hydrogenolysis reaction Nian Lei, Zhili Miao, Fei Liu, Hua Wang, Xiaoli Pan, Aiqin Wang, Tao Zhang 2020, 41 (8):  1261-1267.  DOI: 10.1016/S1872-2067(20)63549-5 Abstract ( 73 )   [Full Text(HTML)] () PDF (1168KB) ( 188 )   The selective hydrogenolysis of glycerol to 1,3-propanediol is a highly important reaction for both improving the profitability of biodiesel and valorization of biomass. While intensive research efforts have been devoted to enhancing the catalytic activity and selectivity, little is focused on the stability although the latter is of paramount importance to practical applications. In this work, we investigated the stability of Pt/WO3/Al2O3 and observed a continuous deactivation trend during a 700 h time-on-stream run. Neither the leaching of active W nor the coking was responsible for the deactivation. Instead, XRD, HAADF-STEM and CO chemisorption results clearly showed the occurrence of significant aggregation of Pt particles, which caused a remarkable decrease of Pt-WOx interfacial sites. As a consequence, strong Brönsted acid sites which were in situ formed by H2 dissociation at the Pt-WOx interfacial sites were reduced, leading to the deactivation of the catalyst.

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Role of ball milling during Cs/X catalyst preparation and effects on catalytic performance in side-chain alkylation of toluene with methanol Qijun Yu, Jinzhe Li, Changcheng Wei, Shu Zeng, Shutao Xu, Zhongmin Liu 2020, 41 (8):  1268-1278.  DOI: 10.1016/S1872-2067(20)63567-7 Abstract ( 85 )   [Full Text(HTML)] () PDF (1182KB) ( 178 )   Supporting Information Ball milling modification was performed on Cs/X catalysts before or after cesium ion exchange. Multiple characterization results (such as pyridine-FTIR, XPS, and solid-state NMR) demonstrated that ball milling played a distinct role in these two different preparation procedures of the catalyst. Ball milling performed after the cesium modification has a strong influence on the Cs/X structure and acid-base properties, which results in the enhancement of the catalytic performance for side-chain methylation of toluene with methanol. Detailed studies revealed that ball milling intensified the interactions between oxides and molecular sieves, which not only increased the dispersion of the Cs species but also generated some weaker basic centers. It is proposed that the new basic centers could be Si-O-Cs and Al-O-Cs, which are produced by breaking of the Si-O-Al bonds of the zeolite framework under the synergetic effect of ball milling and alkali treatment. These new active sites may help to promote the side-chain methylation reaction. However, excessive ball milling will lead to the vanishing of zeolite micropores, thus deactivating side-chain methylation activity, which indicates that microporosity plays a key role in side-chain methylation and individual basic centers cannot catalyze this reaction.

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Geometric effect promoted hydrotalcites catalysts towards aldol condensation reaction Huimin Wang, Weihan Bing, Chunyuan Chen, Yusen Yang, Ming Xu, Lifang Chen, Lei Zheng, Xiaolin Li, Xin Zhang, Jianjun Yin, Min Wei 2020, 41 (8):  1279-1287.  DOI: 10.1016/S1872-2067(20)63556-2 Abstract ( 85 )   [Full Text(HTML)] () PDF (734KB) ( 194 )   Supporting Information In solid basic catalysis field, how to achieve optimized activity and desired stability through elaborate control over basic site properties remains a challenge. In this work, taking advantage of the structure memory effect of layered double hydroxides (LDHs), rehydrated Ca4Al1-xGax-LDHs and Ca4Al1-xInx-LDHs catalysts were prepared and applied in aldol condensation reaction that isobutyraldehyde (IBD) reacts with formaldehyde (FA) to obtain hydroxypivalaldehyde (HPA). Notably, the resulting re-Ca4Al0.90Ga0.10-LDHs exhibits an extraordinarily-high catalytic activity (HPA yield:72%), which is to our best knowledge the highest level in this reaction. The weak Brönsted basic site, 7-coordinated Ca-OH group, which serves as an active site, catalyzes the condensation process and promotes the product desorption. Studies on structure-property correlations demonstrate that Ga as a structural promoter induces a moderate expansion of the laminate lattice, which results in a significant increase in the concentration of weak basic sites in re-Ca4Al0.90Ga0.10-LDHs, accounting for its high catalytic activity. This work illuminates that geometric structure of basic active sites can be tuned via introducing catalyst additive, which leads to a largely improved performance of hydrotalcite solid basic catalysts towards aldol condensation reaction.

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Asymmetric photocatalysis over robust covalent organic frameworks with tetrahydroquinoline linkage Chunzhi Li, Yinhua Ma, Haoran Liu, Lin Tao, Yiqi Ren, Xuelian Chen, He Li, Qihua Yang 2020, 41 (8):  1288-1297.  DOI: 10.1016/S1872-2067(20)63572-0 Abstract ( 109 )   [Full Text(HTML)] () PDF (2224KB) ( 335 )   Supporting Information The asymmetric photocatalytic organic synthesis (APOS) process is a sustainable and environmentally benign method for the production of optically active chemicals with sunlight as an energy source. However, it still lacks efficient semiconductors with tunable band structures and has a low recycling stability. Herein, we report the synthesis of tetrahydroquinoline-linked covalent organic frameworks (QH-COFs) with irreversible tetrahydroquinoline linkage as efficient semiconductors for the visible-light-driven asymmetric α-alkylation of aldehydes by merging with a chiral secondary amine. Up to 94% ee was obtained over QH-COFs, and the activity of QH-COFs was significantly higher than those of inorganic semiconductors (e.g., TiO2, BiVO4, and WO3) under similar conditions, which is mainly attributed to their narrow band gap and suitable band edge. As far as we know, QH-COFs are the most active semiconductors for asymmetric α-alkylation of aldehydes ever reported. The QH-COFs were prepared via a one-pot Povarov cascade imine formation and cycloaddition reaction using Sc(OTf)3/Yb(OTf)3 as Lewis acid catalysts. Attributed to the tetrahydroquinoline linkage, QH-COFs showed extremely high recycling stability, which made practicals application possible. This work not only opens up a new avenue for asymmetric photocatalysis but also provides an efficient and general method for the construction of robust COFs.

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Elucidating structure-performance correlations in gas-phase selective ethanol oxidation and CO oxidation over metal-doped γ-MnO2 Panpan Wang, Jiahao Duan, Jie Wang, Fuming Mei, Peng Liu 2020, 41 (8):  1298-1310.  DOI: 10.1016/S1872-2067(20)63551-3 Abstract ( 68 )   [Full Text(HTML)] () PDF (1603KB) ( 184 )   Supporting Information Despite of considerable efforts on the MnO2-based catalytic combustion, the different structural and component requirements of MnO2 for gas-phase selective oxidation and complete oxidation largely remain unknown. By comparing four types of MnO2 with different crystal structures (α, β, γ and δ), γ-MnO2 was found to be the most efficient catalyst for both aerobic selective oxidation of ethanol and CO oxidation. The structural effect of γ-MnO2 was further investigated by doping metal ions into the framework and by comparing the catalytic performance in the gas-phase aerobic oxidation of CO and ethanol. Among ten M-γ-MnO2 catalysts, Zn-γ-MnO2 showed the lowest temperature (160℃) for achieving 90% CO conversion. The CO oxidation activity of the M-γ-MnO2 catalysts was found to be more relevant to the surface acidity-basicity than the reducibility. In contrast, surface reducibility has been demonstrated to be more crucial in the gas-phase ethanol oxidation. Cu-γ-MnO2 with higher reducibility and more oxygen vacancies of Mn2+/Mn3+ species exhibited higher catalytic activity in the selective ethanol oxidation. Cu-γ-MnO2 achieved the highest acetaldehyde yield (75%) and space-time-yield (5.4 g gcat-1 h-1) at 200℃, which are even comparable to the results obtained by the state-of-the-art silver and gold-containing catalysts. Characterization results and kinetic studies further suggest that the CO oxidation follows the lattice oxygen-based Mars-van Krevelen mechanism, whereas both surface lattice oxygen and adsorbed oxygen species involve in the ethanol activation.