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Hydrogen production from vegetable oil via a chemical looping process with hematite oxygen carriers has been carried out in a fixed-bed reactor at 1023.15–1173.15 K. The lattice oxygen release process and crystalline transformation for the oxygen carrier in the reaction process are investigated. Results indicate that the maximum H 2 composition achieved in the chemical looping hydrogen stage is over 91.72% when hematite oxygen carriers consisting of Fe 2 O 3 , Al 2 O 3 and SiO 2 are used. The active component Fe 2 O 3 in oxygen carriers represents three reduced peaks corresponding to the crystalline form transition from Fe 2 O 3 to Fe 3 O 4 . Up to 96.13% of the lattice oxygen in Fe 2 O 3 can be consumed in the reduction process. The deep reduction of FeO to Fe represents a lower reaction rate with the exhaustion of the lattice. The maximum carbon conversion efficiency of vegetable oil of 79.10% when the ratio of water to oil is 1.2 and hydrogen-rich gas with a highest concentration of 91.72% are achieved in the chemical looping reforming stage and H 2 production stage, respectively. The impurities in the gas are ascribed to the carbon deposition and steam reaction in the chemical looping process. The micrographs of fresh and used oxygen carriers present irregular and blocky structures, sintering is not observed after the multi-cycle reaction process. The crystalline form and reaction activity remain stable after 20-cycle experiments, suggesting that the hematite oxygen carrier is a promising candidate for hydrogen generation from vegetable oil via the chemical looping process. [ABSTRACT FROM AUTHOR]

The structures and electronic properties of different Co2P-supporting configurations on the rutile TiO2(110) surface have been investigated by first-principles density functional theory (DFT) calculations. A number of possible structural candidates and adsorption sites have been considered, while the calculations are executed on periodic systems using slab model. Our results indicate that the O atoms on TiO2(110) turn out to be preferable for the cluster to adsorb by Co atoms, with the largest adsorption energy of 211.50kJ/mol in the most favorable model. According to the Mulliken charge analysis, the Co2P cluster carries a significant positive charge after adsorption, due to the charge transfer occurring from the adsórbate to the substrate. Moreover, the frontier molecular orbital analysis shows that the cluster-surface binding occurs mostly through the interplay of filled Co 3d orbital with unoccupied eigenstates of surface localized on O 2p orbital, which can be also corroborated by the projected density of states investigations, while the lowest unoccupied molecular orbital is mostly contributed by Ti 3d orbital of the surface. In addition, of particular significance is that deposition of Co2P on the rutile TiO2(110) surface results in a small band gap narrowing vis-a-vis the pure surface, yielding a positive effect on catalytic activity. [ABSTRACT FROM AUTHOR]

The development of a stringent sensor to detect low levels of acetone, yielding the potential for the point-of-care clinical diagnosis of diabetes, is still a great challenge but is urgently required. Most studies have focused on Ti 3 C 2 T x , yet other types of MXenes with good performance are rare. Herein, an emerging kind of MXene, V 4 C 3 T x , has been prepared from V 4 AlC 3 via the selective etching of the Al layer using aqueous HF at room temperature (RT), and its performance as an acetone sensor is presented. A V 4 C 3 T x based acetone sensor delivers good performance, as demonstrated by its low working temperature of 25 °C, low detection limit of 1 ppm (lower than the 1.8 ppm diabetes diagnosis threshold), and high selectivity towards acetone in a mixed gas of acetone and water vapor, hopefully showing promise for application in the much faster and earlier diagnosis of diabetes. V 4 C 3 T x MXene is used for the first time in the field of acetone detection in this work, hopefully opening up a path for the investigation of applications of MXene in gas sensors, and such exciting findings distinguish V 4 C 3 T x as a comparable material to the well-known Ti 3 C 2 T x . In addition, we used DFT calculations to explore the mechanisms that result in the superior selectivity for acetone with respect to water vapor. Hopefully, the proposed mechanisms combining experimental results and theoretical study will shed light on the design and production of new high-performance acetone sensors., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Using the recently developed stochastic surface walking global optimization method, this work explores the potential energy surface of TiO2 crystals aiming to search for likely phases with higher photocatalytic activity. Five new phases of TiO2 are identified and the lowest energy phase transition pathways connecting to the most abundant phases (rutile and anatase) are determined. Theory shows that a high-pressure phase, α-PbO2-like form (TiO2II) acts as the key intermediate in between rutile and anatase. The phase transition of anatase to rutile belongs to the diffusionless Martensitic phase transition, occurring through a set of habit planes, rutile(101)//TiO2II(001), and TiO2II(100)//anatase(112). With regard to the photocatalytic activity, three pure phases (#110, pyrite and fluorite) are found to possess the band gap narrower than rutile, but they are unstable at the low-pressure condition. Instead, a mixed anatase-TiO2II phase is found to have good stability and narrower band gap than both parent phases. Because of the phase separation, the mixed phase is also expected to improve the photocatalytic performance by reducing the probability of the electron-hole pair recombination.

The effect of S-TE (solubilization by thermophilic enzyme) pretreatment on excess sludge solubilization and changes of chemical components under microaeration and different temperatures was investigated. The results showed that, two reaction mechanisms of enzyme-catalyzed reaction and thermal-hydrolyzed reaction were involved in the S-TE process, which began with depolymerization of sludge flocs by exoenzymes including proteases and amylases, followed by cell-walls and organic matters disintegration and hydrolyzation. The solubiozation process with thermophilic bacteria Bacillus stearothermophilus sp. AT06-1 addition was enhanced compared with the control (the process without the bacteria). Under the optimum temperature (65 degrees C), the solubilization rate of total suspended solid (TSS) and volatile suspended solid (VSS) reached 34.09% and 24.16% within 2 days respectively, 7.57% and 6.87% higher than the control. The results also revealed that under microaeration operation, the maximal soluble chemical oxygen demand (SCOD) of 4,531 mg/L and volatile fatty acid (VFA) of 2,319 mg/L were obtained, which would be beneficial to the followed anaerobic digestion process. At the same time the activity of protease was dramatically promoted. The protein released from the sludge was hydrolyzed, resulting in an increase of protein concentration at the early stage of the experiment and then a decrease at the later period.