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Ammonia has sparked a lot of interest as a promising hydrogen carrier for the development of renewable energy and as a workable method to produce CO x -free hydrogen for fuel cells through its on-site decomposition. The catalysts, composed of nickel as an active metal supported on the Y 2 O 3 , were synthesized by the sol-gel self-combustion method conveniently, in which the active metals are uniformly dispersed. 700–1.25Ni 1 Y 1 O α exhibits the best catalytic activity and has the most active metal dispersion (6.15 %). The ammonia conversion can reach 96 % at 550 °C and 12000 ml·g cat −1·h−1 gas hourly space velocities (GHSVs) as well as 100 % at 600 °C and the same GHSVs. Temperature-programmed reduction, temperature-programmed desorption, and X-ray photoelectron spectroscopy were used to characterize the catalysts. It was found that 700–1.25Ni 1 Y 1 O α has the best capacity for hydrogen desorption resulting in weakening the inhibitory effect of hydrogen to the reaction and enhancing the reactivity of the catalyst. The electron transfer from Y in Y–O–Ni structure increases gradually as the Ni to Y ratio becomes appropriate, enhancing the alkalinity of the catalyst and electron density around the Ni, which is beneficial to NH 3 decomposition. [Display omitted] • Catalysts prepared by sol-gel self-combustion are efficient and stable for NH 3 to H 2. • An appropriate Ni to Y ratio can enhance the formation of the Y–O–Ni structure. • Catalyst 700–1.25Ni 1 Y 1 O α has the strongest electron transfer ability in Y–O–Ni. • Catalyst 700–1.25Ni 1 Y 1 O α shows the most excellent ability of H 2 desorption. • NH 3 conversion of 96 % can be achieved by 700–1.25Ni 1 Y 1 O α at 550 °C. [ABSTRACT FROM AUTHOR]

• Catalysts modified by rare earth metals have efficient catalytic performance. • Inhibition of H 2 is greatly suppressed over 10Ni/A 1 Mg 4 O α. • Solid solution formed and induced surface defects in 10Ni/A 1 Mg 4 O α. • Stronger basicity modified by La and Ce performed to promote electron donate to Ni sites. • Ce and Y greatly improve the intrinsic activity of catalysts. The lack of detailed functions of different REMs in NH 3 decomposition to H 2 makes the efficient modified catalysts not rationally be designed though many REMs-modified catalysts have been reported. In this work, the 10Ni/A 1 Mg 4 O α (A = La, Ce, and Y) and 10Ni/MgO, in which supports were synthesized by the sol–gel method and Ni was loaded by the wet-impregnate method, were comparatively investigated to reveal the effect of REMs against NH 3 decomposition reaction. The presence of REMs enhanced the activity of 10Ni/A 1 Mg 4 O α and decreased the activation energy as greatly as by half compared to 10Ni/MgO. The produced H 2 in situ has little impact on the activity of 10Ni/A 1 Mg 4 O α , among which Ce has the most excellent H 2 desorption ability. The intrinsic activity of catalysts was improved better by Ce and Y than La and the best Ni particle size is around 6 nm according to TOF, though the Ni particle is the smallest (4.9 nm) in 10Ni/La 1 Mg 4 O α. The surface structure of catalysts was tuned by doping REMs, forming a solid solution and some defects (oxygen vacancies), which enhanced the interaction between active metal and support with obvious electron transfer from support to Ni obtaining a better Ni dispersion and making NiO easier to be reduced. Additionally, the catalysts doped by La or Ce possess more oxygen vacancy due to the changes of La 2 O 2 CO 3 and the valence of Ce, exhibiting stronger basic sites and better N 2 desorption capacity. The study offers a promising strategy for utilizing appropriate or multiple REMs to synthesize effective catalysts effectively for catalyzing NH 3 decomposition in the future. [ABSTRACT FROM AUTHOR]

[Display omitted] • A mechanism for sulfur poisoning the Ni/Al 2 O 3 catalyst was proposed. • The main factor accelerating catalyst poisoning is the migration of elemental S. • The catalyst adding 1.0% SiO 2 exhibits improved sulfur tolerance. • Smaller Ni particles are more sulfur-tolerant than larger ones. Dry reforming of methane (DRM) is the method to convert two greenhouse gases to synthesis gas. The nickel-based catalysts used in the DRM are extremely easily poisoned by H 2 S in the feed gas, however, the associated poisoning process is not clear. In this work, a mechanism for poisoning the Ni/Al 2 O 3 catalyst by elemental sulfur migration was proposed, and silica was added to the catalyst to prolong the sulfur tolerance of the catalyst. From the characterizations of the catalyst with different methods, it was noted that the main factor accelerating catalyst poisoning was the formation and migration of elemental sulfur. The catalyst Ni/Al 2 O 3 with 1.0 % SiO 2 exhibited improved sulfur tolerance. The addition of SiO 2 inhibits the growth of Ni particles during the reduction process, and the smaller Ni particles lead to less coke and a longer period of sulfur tolerance. [ABSTRACT FROM AUTHOR]

• Catalytic upgrading of bio-oil was conducted over metal oxide-modified Y zeolite. • The upgraded bio-oil by Fe/Y, Mg/Y and Zn/Y was rich in aromatics and phenols. • Ni/Y catalyst exhibited good selectivity to phenol and cresol. Pyrolysis as one of the most utilizations of biomass has aroused the increasing attention, however, the key is to upgrade biomass pyrolysis volatiles and enrich the high-valued chemicals in bio-oil. In this paper, different metal oxide-modified Y zeolites, including Fe/Y, Co/Y, Ni/Y, Mg/Y and Zn/Y, were prepared by wet impregnation and employed in catalytic upgrading of pyrolytic volatiles from rice straw (RS) and poplar sawdust (PS). Results showed that the modification by metal oxides led to the decrease of surface area and the changes in the acidity of zeolites. Higher yields of gas and water were obtained over metal oxide-modified zeolites at the expense of the bio-oil yields. More strong acid sites of the Ni/Y and Zn/Y catalysts promoted the generation of H 2. Fe/Y catalyst showed good selectivity to aromatics in bio-oil owing to high mesoporous volume and strong deoxidization capacity. The highest aromatic hydrocarbons content (63.0%) was obtained over Fe/Y in RS bio-oil. The formation of phenol and cresol was promoted with increasing the ratio of Lewis/Brönsted acid. Under the action of Ni/Y with the highest Lewis/Brönsted ratio, the phenol content in bio-oil from RS and PS pyrolysis was enhanced to 11.8% and 25.3%, respectively. The Fe/Y catalyst had good upgrading performance during three reaction-regeneration cycles. In addition, the possible reaction mechanism of biomass pyrolysis volatiles over metal oxide-modified Y zeolites was proposed. This work will provide a guide for the composition regulation of bio-oil from biomass pyrolysis. [ABSTRACT FROM AUTHOR]

• Core-shell structured Fe 3 C with various melamine/Fe(NO 3) 3 were prepared for CMD. • Mel-2.0 exhibited better catalytic activity owing to smaller Fe 3 C nanoparticles. • Mel-2.0–850 spent 7 times longer than Mel-2.0–700 to keep CH 4 conversion above 20%. • H 2 output increased to 3482 mmol/g cat in the 4th reaction-CO 2 regeneration cycle. • More Fe 3 C and less metal Fe are beneficial for methane decomposition. Fe 3 C as an intermediate often can be detected during catalytic decomposition of methane over Fe-based catalysts due to the dissolving of carbon in the bulk of Fe. However, the activity of Fe 3 C for methane decomposition is still unclear. In this work, Fe 3 C nanoparticles were prepared using melamine as carbon source mixed with Fe(NO 3) 3 via sol–gel method. The effects of the ratio of melamine to Fe(NO 3) 3 , reaction temperature and CO 2 -regeneration performances on catalytic methane decomposition (CMD) were investigated on a fixed-bed reactor. Results showed that the prepared catalyst performed better catalytic activity and stability for methane decomposition owing to smaller Fe 3 C nanoparticles with better dispersion, and typical core–shell structure with Fe 3 C core surrounded by carbon shell was obtained when the ratio of melamine to Fe(NO 3) 3 was 2:1. The reaction temperature significantly affected the activity and stability. About 13.2% of CH 4 conversion and 733 mmol/g cat hydrogen output were obtained at 850 °C after 700 min. Besides, the spent catalysts were regenerated by CO 2. With the increase of regeneration times, the activity and stability of catalyst decreased firstly and then increased. About 96.1% initial CH 4 conversion and 13.5% CH 4 conversion were obtained after reaction of 3500 min for the 4th cycle, along with 3482 mmol/g cat hydrogen output. And the mechanism models of CMD reaction and CO 2 -regeneration over Fe 3 C catalysts was proposed. This work provides a new idea to solve metal sintering problem in catalytic methane decomposition and improve the stability of catalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tar yields obtained from the pyrolysis of different rubbers exceed 90 wt%. • Tar compositions from rubber pyrolysis are related to their molecular structure. • Co-pyrolysis promotes the gas generation and inhibits the char formation. • Interaction between NR and SBR promotes the cycloolefin and chain olefin formation. • Co-pyrolysis of SBR and BR contributes to the formation of aromatic hydrocarbons. Pyrolysis of waste tire (WT) is an efficient method to convert it into fuels and high-value chemicals. However, the main organic components of tire including natural rubber (NR), styrene butadiene rubber (SBR) and butadiene rubber (BR) usually exert interaction during pyrolysis. To investigate the interactions between different rubbers, individual pyrolysis and co-pyrolysis of three pure rubbers were conducted using an infrared-heating fixed-bed reactor, and the synergy during co-pyrolysis was revealed based on products distribution, tar quality and compositions from pyrolysis of pure rubber and waste tire. The results show that tar yields from rubber pyrolysis exceed 90 wt% and tar compositions are related to the molecular structures of rubbers. Co-pyrolysis between different rubbers promotes gases formation and inhibits char formation. The interaction between NR and SBR facilitates the formation of cycloolefin and chain olefin, but co-pyrolysis of SBR and BR contributes to the aromatic hydrocarbons formation. Similar tar components from pyrolysis of demineralized waste tire as those from pyrolysis of NR/SBR/BR sample indicate that waste tire pyrolysis contains individual pyrolysis and co-pyrolysis of different rubbers. The potential reaction process of WT was also proposed. The insight on interaction between different rubbers will provide a good guide for efficient pyrolysis of waste tire. [ABSTRACT FROM AUTHOR]

We developed a novel electrochemical biosensor for uracil-DNA glycosylase (UDG) detection based on enzyme-free and substrate-free electrocatalytic signal amplification by porphyrin-based covalent-linked nanomaterial (OAPS-Por). This OAPS-Por could not only absorb much Thionine (Thi), but also possess obvious electrocatalytic activity toward the reduction of Thi without involvement of H 2 O 2. Sequentially, the functionalized OAPS-Por with Thi, Au nanoparticles and single-stranded DNA (OAPS-Por/Thi@AuNPs-ssDNA) was ingeniously designed as the signal probe. Meantime, the hairpin DNA (hDNA) with four uracil bases was immobilized on AuNPs/GCE via an Au–S bond. When UDG was present, the uracil in hDNA was removed and hairpin structure was unfolded. Next, the signal probes binded with the unfolded hDNA by DNA hybridization. The Thi in signal probes could generated an original electrochemical signal, which could be further amplified and output due to the robust electrocatalytic activities of OAPS-Por toward Thi. As a result, the as-constructed electrochemical biosensor had a broad linear range from 0.005 to 1 U mL-1. It also exhibited a low detection limit of 6.97 × 10-4 U mL-1. Moreover, this biosensor could be used to assay the inhibition of UDG (UGI) and the UDG activity in real samples (HeLa cell lysates and human blood serums), and demonstrated great prospect in clinical diagnostics and biomedical research. • A novel electrochemical biosensor is developed for sensitive detection of uracil-DNA glycosylase (UDG). • This biosensor is based on nonenzymatic nanomaterial (OAPS-Por) signal amplification. • OAPS-Por exhibited intrinsic electrocatalytic activity toward the reduction of absorbed Thi without involvement of H 2 O 2. • This biosensor shows low limit of detection and wide linear range of UDG activity. [ABSTRACT FROM AUTHOR]

Highlights • A novel porphyrin-based porous organic polymer (PPOP) is designed and prepared. • Large surface area with adequately exposed catalytic active sites of the PPOP ensures its high peroxidase-like activity. • A versatile colorimetric biosensor for H 2 O 2 , glucose and three antioxidants detection with high sensitivity and stability is established with PPOP. • The distinguishing inhibitory behaviors of three antioxidants to PPOP imply different antioxidative mechanisms. Abstract As promising alternatives to natural enzymes, catalytically active nanomaterials (nanozymes) are of great interest due to their high activity, controlled synthesis, low-cost, and excellent stability against stringent conditions. Studies of the chemical interactions between antioxidants and nanozymes would provide valuable information about catalytic mechanisms, help to better understand some metabolic pathways and screen more effective artificial enzymes. In this work, a porphyrin-based porous organic polymer, named FePPOP-1 was synthesized via a Sonogashira–Hagihara coupling reaction between 1,3,5-triethynylbenzene and iron 5,10,15,20-tetrakis-(4′-bromophenyl)porphyrin (FeTBrPP). FePPOP-1 possesses large BET surface area as well as high thermal and chemical stability. The good peroxidase-like activity of FePPOP-1 was confirmed by catalyzing the oxidation reaction of 3,3′,5,5′-Tetramethylbenzidine (TMB) with H 2 O 2. A FePPOP-1 based colorimetric biosensor was then established for H 2 O 2 , glucose and three antioxidants [ascorbic acid (AA), gallic acid (GA) and tannic acid (TA)] detection with high sensitivity and stability. Moreover, the inhibitory effects of these three natural antioxidants on peroxidase-like activity of FePPOP-1 and the relative strength of their anti-oxidative capacity were comparatively investigated. The distinguishing inhibitory behavior of AA, GA and TA implied their different anti-oxidative mechanisms. [ABSTRACT FROM AUTHOR]